Lung Cancer Resistance to Chemotherapy
`
`David J. Stewart
`
`Abstract Metastatic lung cancer remains incurable by chemotherapy. Several factors
`contribute to resistance to chemotherapy, including many factors that are adaptations
`of systems that evolved to protect normal cells from a hostile environment. 'I‘11mor
`cell characteristics, tumor cell interactions with extracellular matrix and stromal
`
`cells, and tumor physical characteristics all contribute to resistance. Resistance may
`arise from gene upregulation or downregulation as a downstream consequence of the
`oncogene mutations or tumor suppressor gene deletions that underlie tumorigenesis
`or may also arise due to tumor hypoxia or due to exposure to therapy. Host gene poly-
`morphisms may alter resistance by determining the half-life or enzymatic activity of
`upregulated resistance factors. Resistance may arise from decreased drug delivery to
`tumor, impact of extracellular pH on drug uptake, altered drug uptake transporters or
`cell membrane characteristics, increased drug efflux or detoxification, decreased drug
`binding, altered drug targets, increased DNA repair, decreased proapoptotic factors,
`increased antiapoptotic factors, altered cell cycling or mitotic checkpoints, or altered
`transcription factors. This diversity of resistance mechanisms magnifies the chal-
`lenges facing us in predicting patient prognosis and in overcoming resistance.
`
`Keywords Lung cancer - Chemotherapy - Resistance
`
`Lung Cancer and Resistance
`
`As outlined elsewhere in this text, despite 20-50% of patients with advanced
`non-small cell lung cancer (NSCLC) and 60-80% of patients with extensive small
`cell lung cancer (SCLC) initially responding to chemotherapy, Widely metastatic
`
`D.J. Stewart(B])
`Department of Thoracic/Head & Neck Medical Oncology,
`University of Texas M.D. Anderson Cancer Center, Houston, TX, USA
`e-mail: dstewart@mdanderson.org
`
`D.J. Stewart (ed.), Lung Cancer: Prevention, Management, and Emerging Therapies,
`Current Clinical Oncology, DOI 10.1007/978-l-60761-524-8_l5,
`© Humana Press, a part of Springer Science+Business Media, LLC 2010
`
`331
`
`AVENTIS EXHIBIT 2027
`Mylan v. Aventis
`IPR2016-00627
`
`AVENTIS EXHIBIT 2027
`Mylan v. Aventis
`IPR2016-00627
`
`

`
`332
`
`D.J. Stewart
`
`disease cannot be cured since almost all tumors, that are not intrinsically resistant,
`rapidly develop acquired broad cross-resistance to therapy. The mechanisms by which
`tumors become resistant to chemotherapy are generally adaptations of mecha-
`nisms that have developed through evolution to protect normal tissues from a
`hostile environment. The observation that many genes often concurrently have
`altered expression within the same resistant lung cancer
`suggests that resis-
`tance is generally due to the cumulative effect of sever
`rs acting together,
`rather than being due to the effect of just one or a few f
`he fact that tumor
`gene expression arrays-and in vitro sensitivity testing
`are highly accurate
`in predicting clinical resistance but less accurate in predicting sensitivity in lung
`cancer suggests that tumor cellular factors alone are sufficient to cause resistance,
`but that in vivo tumor physical characteristics and host factors may preclude
`response despite the presence of intrinsically sensitive tumor cells. In addition,
`while drug efficacy differs somewhat across types of lung cancer preclinically
`— there are also substantial similarities, and the broad cross-
`resistance seen between chemotherapy agents in both preclinical ‘and
`clinical 2 studies suggests that factors that render a tumor resistant to one
`agent will also often render it resistant to most other agents.
`
`
`
`Types of Resistance
`
`Resistance is often classified as “intrinsic” vs. “acquired.” As outlined in Ta
`it can also be classified as “active” (due to excess of a resistance factor) vs. ‘
`
`,
`-
`
`saturable passive” (due to mutation or alteration of a factor) vs. “saturable pas
`(due to deficiency or saturation of a factor required for drug efficacy)
`Flattening of dose—response curves at higher chemotherapy dosesjsuggests that
`resistance due to deficiency or saturation of factors required for drug efficacy
`(e.g., as a result of gene silencing through drug-induced DNA hyperrnethylation
`- may be particularly important
`in NSCLC and other epithelial
`tumors.
`Resistance may also be “accelerated” (due to rapid tumor cell repopulation) or
`“quiescent” (from insufficient cycling through sensitive phases of the cell cycle, with
`the quiescent resistance being related in some cases to broad downregulation of
`
`Table 1 Examples of ways to classify resistance
`
`Intrinsic vs. acquired
`Active vs. non-saturable passive vs. saturable passive
`Quiescent vs. accelerated
`Due to:
`
`Mutation vs. epigenetic
`Host factors vs. tumor factors
`
`Tumor cell factors vs. microenvironment/stromal factors vs. abscopal effects of a distant
`resistant tumor
`
`

`
`Lung Cancer Resistance to Chemotherapy
`
`333
`
`membrane transporters- to reversible senescence—).
`Furthermore, resistance may be “genetic” (due to resistance-generating mutations)
`or “epigenetic” (due to upregulation or downregulation of expression of relevant
`genes), and it may be related to tumor cell characteristics, stromal characteris-
`tics, or host factors. Tumors in one part of the body may render tumors at a distance
`resistant I possibly through mobilization of protective mesenchymal stem cells
`from the bone marrow. All of these mechanisms probably play a role in rendering
`advanced lung cancer incurable.
`
`Importance of the Host Genotype
`
`Tumors inherit the genotype of the host, in addition to having tumor-specific
`mutations. Gene polymorphisms inherited from the host may modulate resistance
`by altering the enzymatic activi
`or protein half-life of a resistance factor, such as
`a DNA repair protein (Table
`correlation of chemotherapy-induced leukopenia
`with tumor response in SC
`is in keeping with a link between host genotype
`and tumor sensitivity to therapy. Little is known regarding the relative importance
`of host-derived factors vs. tumor-specific factors in resistance, and it is likely that
`both play a role. The number of copies of a gene for a resistance factor may be
`higher in tumor than in normal cells (due to gene amplification or polyploidy),
`and tumor-specific factors could also affect gene transcription and posttranscrip-
`tional modifications of the resistance factor, but the protein expression of the resistance
`factor could also be increased or decreased if the host polymorphisms are associated
`
`
`
`Table 2 Genes for which host genetic polymorphisms have been reported to contribute
`to resistance
`
`Factor
`
`MRP2
`MDR1/p-glycoprotein
`Glutathione-S-transferase-It
`Deoxycytidine deaminase
`ERCC1
`Xeroderma pigmentosum C
`Xeroderma pigmentosum D
`Xeroderma pigmentosum G
`
`XRCC1
`NQO1
`p53
`Cyclin D1
`
`Agents affected
`
`Cisplatin + irinotecan
`Cisplatin + etoposide or vinorelbine“
`Cisplatin regimens
`Gemcitabine
`Platinum regimens
`Platinum regimens”
`Platinum regimens”
`Platinum regimens
`
`Platinum regimens”
`Platinum regimens
`Platinum regimens
`Platinum regimens
`
`‘No association with outcome in patients treated with cisplatin—docetaxel
`“Data were equivocal or negative in some individual trials
`
`

`
`334
`
`D.J. Stewart
`
`with increased or decreased half-life of the protein, and for a given degree of
`expression, the effect of the resistance factor could vary with polymorphisms that alter
`the enzymatic activity of the factor.
`Host gene polymorphisms could also affect drug efficacy by altering drug metabo-
`lism. In NSCLC patients, efficacy correlated with cytochrome p450 polymorphisms
`in patients receiving vinorelbine-based chemotherapy‘, and efficacy and toxic-
`ity correlated with uridine diphosphate-glucuronosyltransferase polymorphisms in
`patients receiving irinotecan plus cisplatin-.
`
`Chemotherapy as “Targeted” Therapy
`
`tubulin,
`including DNA,
`Chemotherapy agents may hit a variety of targets,
`topoisomerases, a variety of other enzymes, etc. However, little is known about
`how chemotherapy agents achieve the selectivity that permits major tumor shrinkage
`with relatively little damage to most normal organs. An early concept was that the
`major selectivity factor was the rapid growth of tumor cells. However, the obser-
`vation that agents like cisplatin can shrink cancers while causing minimal damage
`to bone marrow, gastrointestinal mucosa, skin, or other rapidly proliferating
`normal tissues indicates that tumor growth rate is not necessarily the factor
`conferring selectivity. While substantial attention has been paid to the investiga-
`tion of factors that render tumors resistant, much less attention has been paid to
`characteristics or “targets” that are required in order for a tumor to be sensitive to
`a chemotherapy agent.
`Below, we discuss mechanisms of acquisition of resistance or loss of sensitivity
`that have been investigated in lung cancer cell lines and xenografts (Table-, and that
`pertain to commonly used standard chemotherapy agents. We also outline factors that
`have been assessed in human lung cancer samples and that appeared to alter drug
`efficacy (Table -, as well as presenting factors that did not correlate with treatment
`efficacy clinically despite modulating resistance in preclinical systems (Table
`
`Drug and Oxygen Delivery
`
`Drug delivery to tumor cells may be limited primarily by tumor blood flow (“flow-
`limited” drugs) or may be limited primarily by cell membrane characteristics
`(“membrane-limited” drugs)- Tumor blood flow may be reduced by high tissue
`pressure, high serum fibrinogen, decreased red blood cell membrane deformability,
`and impaired blood flow autoregulation
`emcitabine delivery appeared to be
`flow-limited in a SCLC model. w
`ious observations suggest that cis-
`platin delivery may be membrane-limit
`and relatively little is known about
`other agents.
`
`
`
`

`
`Lung Cancer Resistance to Chemotherapy
`
`335
`
`Table 3 Tumor factors contributing to lung cancer resistance in cell lines or xenografts
`
`Factor (expression or activity)
`Decreased tumor blood flow
`
`1 Drug delivery
`1 Oxygen delivery
`
`1 HIF-I0.
`
`Alterations of tumor extracellular pH
`i PH
`T PH
`Decreased drug uptake
`1 Cell membrane rigiditylsphingomyelinl
`cholesterol
`
`1 Long chain and unsaturated fatty acids
`1 CTR1
`1 Multiple membrane transporters
`1 Na’', K’' ATPase/‘[ thromboxane A2/T sorbitol
`1 Human equilibrative nucleoside transporter 1
`Increased drug efflux
`1 MRP/GS-X
`
`1 MDR1/p-glycoprotein“
`T RLIP76/RALBP1
`1 Lung resistance protein“
`1 P-type adenosine triphosphatase 7B
`Increased drug detoxification
`T Glutathione
`
`T Glutamate-cysteine ligase
`T Glutafl1ione peroxidase/glutafl1ione reductase
`T Glutathione-S-tIansferase-rt
`1 Metallothioneins
`T Dihydrodiol dehydrogenase
`
`T Thyrnidine and folate pools
`T Peroxiredoxin V
`
`T Deoxycytidine dearninase
`Decreased drug activation
`1 Deoxycytidine ldnase activity
`Decreased drug binding/‘[ intracellular pH
`Increased, decreased or altered target
`1 Folate pathway enzymes
`1 Stathrnin (oncoprotein 18)
`1 Class 1]] [3 tubulin (+/ — or tubulin)
`
`1 or mutated Topoisomerase II-or
`T Fragile histidjne triad gene
`
`Agents affected
`
`All?
`
`Etoposide, paclitaxel (not cisplatin,
`topotecan)
`Cisplatin, doxorubicin, paclitaxel
`
`Weak bases (doxorubicin, vinca alkaloids)
`
`Weak acids (platjnums, alkylating agents)
`
`Platinums, etoposide, paclitaxel
`
`Platinums
`Platinums
`Platinums
`Platinums
`Gemcitabine
`
`Platinums“, anthracyclines, vincas,
`etoposide, taxanes, gemcitabine“
`Anthracyclines, vincas, etoposide, taxanes
`Vinorelbine, doxorubicin
`
`Cisplatin“, etoposide“
`Cisplatin
`
`Cisplatin, etoposide“, anthracyclines“,
`vincas“, camptofl1ecins, mitomycin,
`alkylating agents, methotrexate,
`radiation
`
`Cisplatin
`Cisplatin
`Cisplatin“
`Cisplatin, etoposide
`Cisplatin, doxorubicin, taxanes, vincas,
`melphalan
`Pemetrexed
`
`Doxorubicin, etoposide
`Gemcitabine
`
`Gemcitabine
`
`Cisplatin
`
`Pemetrexed
`Vincas
`
`Taxanes, vincas“, cisplatin, doxorubicin,
`etoposide
`Etoposide, anthracyclines
`Etoposide, carnptothecins
`
`(continued)
`
`

`
`336
`
`Table 3 (continued)
`
`Factor (expression or activity)
`
`Agents affected
`
`D.J. Stewart
`
`Increased DNA damage repair
`1 Topoisomerase II-0L
`1 Nucleotide excision repair
`1 ERCC1
`T Xeroderma pigmentosum A
`T Ribonucleotide reductase M1
`1 Rad51 (homologous combination repair)
`1 DNA-dependent protein kinase
`1 Husl
`T BRCA1
`1 High mobility group box 2
`1 Fragile histidine triad gene
`1 Thymidylate synthase
`1 Dihydropyrimidine dehydrogenase
`Decreased apoptotic response
`1 DNA mismatch repair
`Mutant p53
`
`1 p53-Binding protein 2
`1 GML protein
`1 Caspase-8 activity
`1 Caspase-9 activity
`1 FUS1
`1 SAPK/c-Jun N-terminal kinase
`1 Bak
`1 Bax“
`1 Apoptosis signal transduction
`Increased apoptosis inhibitors
`1 Cyclooxygenase-2
`
`T Telomerase
`1 Heat shock protein 90
`T PPARy splice variant
`Altered membrane gangliosides
`T Caveolin-1/caveolae organelles
`T Clusterin
`1 Attachment to extracellular matrix/stromal
`cells
`
`1 Big-h3
`T Stromal-cell-derived factor-1/CXCL12
`1 Connexin 32
`1 Epidermal growth factor receptor
`
`Cisplatin, radiation, vincas
`Platinums
`Platinums“
`Platinums
`
`Gemcitabine, cisplatin
`Platinums, etoposide
`Etoposide
`Cisplatin
`Platinums“
`
`Cisplatin
`Cisplatin
`Platinums
`Platinums
`
`Platinums
`
`Cisplatin, etoposide, camptothecin,
`methotrexate, antl1racyclines, radiation,
`taxanes“, others
`
`Cisplatin, radiation
`Cisplatin
`Cisplatin, topotecan, radiation
`Cisplatin
`Cisplatin
`Platinums, gemcitabine
`Cisplatin, etoposide, radiation, Fas ligand
`Cisplatin, etoposide, taxanes, doxorubicin
`Cisplatin, taxanes
`
`Cisplatin, anthracyclines, etoposide,
`vincas, taxanes, gemcitabine
`Cisplatin, docetaxel, etoposide
`Taxanes
`
`Cisplatin
`Cisplatin
`Etoposide, paclitaxel
`Paclitaxel, gemcitabine
`Cisplatin, doxorubicin, taxanes, etoposide,
`others
`
`Etoposide
`Etoposide
`Vrnorelbine
`
`Cisplatin“, doxorubicin, etoposide, vincas,
`taxanes, carnptothecin, pemetrexed,
`gemcitabine, others
`
`(continued)
`
`

`
`Lung Cancer Resistance to Chemotherapy
`
`337
`
`Table 3 (continued)
`
`Factor (expression or activity)
`
`Agents affected
`
`T HER-2/neu (erbB-2, p185)
`
`T STAT3
`1 ERK1/2 and MAPK/ERK kinase
`
`T Hepatocyte growth factor
`T PI3K/Akt pathway activation
`
`T p70S6K and S6 phosphorylation
`T PKC-8
`T PKC-8
`T PKC-0L, PKC-11
`
`1 PKC—B
`T IGF-1R
`T c-myc
`
`T MAPK phosphatase-1
`T Growth hormone releasing hormone
`T Fibroblast growth factor 2
`T Annexin IV
`T Hyaluronan
`T Bcl-2“
`
`T Bcl-XL
`
`T Mcl-1
`T Survivin
`T Livin
`T X-linked inhibitor of apoptosis protein
`(XIAP)
`
`T Inhibitor of apoptosis proteins (IAPs)
`T Nrf2/heme oxygenase-1
`T P21WAF1/CIPI
`
`T TRAIL decoy receptors DcR1 and DcR2
`Altered cell cycling
`Cell cycle phase
`1 Mitotic slippage/1 aneuploidy
`T Aneuploidy
`T RB/1 PRB
`T SKP2
`T E2F4/1 E2F1
`1 CHK2 kinase
`Mitotic spindle checkpoint abnormalities
`T 14-3-3Q
`
`Cisplatin, etoposide, doxorubicin, taxanes,
`gemcitabine“, others
`Cisplatin
`Taxanes“, cisplatin
`Cisplatin
`Cisplatin, etoposide, taxanes, gerr1citabine,
`others
`
`Cisplatin
`Etoposide, doxorubicin
`Etoposide, cisplatin
`Platinums“, vincas, taxanes“, doxorubicin,
`others
`
`Cisplatin, etoposide
`Platinums, etoposide
`Cisplatin
`Cisplatin
`Taxanes
`
`Etoposide
`Taxanes
`
`Cisplatin
`Cisplatin, camptothecin, doxorubicin,
`etoposide, vincas
`Cisplatin, gemcitabine, doxorubicin,
`vincas, taxanes, etoposide, others
`Cisplatin, etoposide, taxanes, radiation
`Cisplatin, gerr1citabine, taxanes
`Etoposide
`Cisplatin, etoposide
`
`Gemcitabine
`
`Cisplatin
`Cisplatin, camptothecin, doxorubicin,
`etoposide
`Doxorubicin, etoposide
`
`Varies with drug
`Taxanes
`
`Etoposide, topotecan, gerncitabine
`Cisplatin, etoposide, taxanes, 5-FU
`Cisplatin, camptothecin, others
`Cisplatin, etoposide
`Cisplatin
`Vinorelbine, taxanes
`
`Cisplatin
`
`(continued)
`
`

`
`338
`
`Table 3 (continued)
`
`D.J. Stewart
`
`Factor (expression or activity)
`
`Agents affected
`
`Increased transcription factors
`1 NF-KB
`
`1 TWIST
`1 SNAIL
`1 Clock
`1 Activating transcription factor 4
`1 HIV-1 Tat interacting protein 60 (Tip60)
`“Not consistent across all studies
`
`Cisplatin, doxorubicin“, etoposide“,
`gemcitabine, taxanes
`Cisplatin
`Cisplatin
`Cisplatin, etoposide
`Cisplatin, etoposide
`Cisplatin
`
`"No association with resistance to platinurns; may sensitize to gemcitabine
`“No association with resistance to anthracyclines, vinca alkaloids, bleomycin, irinotecan/SN-38
`
`“BRCA1 expression sensitized cells to antimicrotubule agents
`“Paradoxical increase in sensitivity to gemcitabine—cisplatin combination in one study
`‘Paradoxical increase in sensitivity to taxanes in some studies
`
`Reduced tumor blood flow also decreases oxygen delivery. Hypoxia may
`directly reduce efficacy of etoposide—, it may increase
`efficacy of topotecan-, and it has little impact on efficacy of cisplatin2
`in lung cancer cells. Hypoxia may also have indirect effects on drug efficacy by
`upregulating the expression of resistance-associated antiapoptotic factors 2 and
`by increasing expression of hypoxia inducible factor-lot (HIF-lot). HIF-lot in turn
`may render NSCLC cells more resistant to cisplatin— and
`paclitaxel - and after initial tumor cell killing by chemotherapy, HIF-10. may
`support accelerated repopulation of tumors by upregulating the expression of the
`vascular endothelial growth factor (VEGF) and platelet derived growth factor
`(PDGF) that support angiogenesis-.
`The role of tumor blood flow and hypoxia in resistance remains uncertain in
`lung cancer patients. By (l8)F-fluoromisonidazole imaging studies, the hypoxic
`cell fraction is low in NSCLC
`I-HF-lot expression in NSCLC tumors resected
`after neoadjuvant cisplatin—ge
`bine did not correlate with patient survival -,
`and prechemotherapy serum
`levels - and tumor VEGF expression by
`immunohistochemistry (IHC)
`did not predict outcome in advanced NSCLC
`
`
`
`patients receiving cisplatin-based combinations.
`
`Extracellular pH
`
`Low extracellular pH augments cellular uptake and cytotoxicity of weak acids such
`as cisplati
`and alkylating agents -, while high extracellular pH augments
`cellular u
`d cytotoxicity of weak bases such as doxorubicin - and vinca
`alkaloids
`nd pH has little net effect on zwitterions like paclitaxel
`The role of pH clinically remains unknown, but both dietary factors and cone
`medications may alter tumor extracellular pH and hence might alter resistance
`
`
`
`

`
`Lung Cancer Resistance to Chemotherapy
`
`339
`
`Table 4 Factors for which some available clinical data support a role in lung cancer resistance
`Factor
`
`Agents affected
`
`Decreased drug uptake
`1 Na’', K’' ATPase
`1 Human equilibrative
`nucleoside transporter 1
`Increased drug efflux
`T MRP/GS-X
`T MDRI/p-glycoprotein
`T Breast cancer resistance
`protein
`T Lung resistance protein
`Increased drug detoxification
`T Glutathione-S-transferase-it
`T Metallothioneins
`
`Increased, decreased or altered target
`1 Stathmin (oncoprotein 18)
`T/Mutated class 111 B tubulin
`1/Mutated topoisomerase II-0L
`Increased damage repair
`T Topoisornerase II-0.
`T Nucleotide excision repair/T
`ERCC 1
`
`T Ribonucleotide reductase Ml
`T BRCAI
`Decreased apoptotic response
`1 DNA mismatch repair
`Mutant p53
`By sequencing
`By II-IC positivity
`J, GML protein
`Increased apoptosis inhibitors
`T Cyclooxygenase-2
`T Heat shock protein 27
`T Caveolin-1
`J, p-ERK
`Mutant K-ras
`
`Platinums“
`Gemcitabine“
`
`Multiple platinum regimens“; vindesine +etoposide
`Multiple regimens“
`Platinum regimens
`
`Platinum regimens“
`
`Platinum regimens“
`Cisplatin—etoposide/CAV
`
`Cisplatin—vinorelbine"
`Taxanes, cisplatin—vinorelbine“
`Etoposide
`
`Cisplatin regimens
`Platinum regimens“
`
`Gemcitabine regimens
`Cisplatin + gemcitabine“
`
`Platinum regimens“
`
`Platinum regimens
`Platinum regimens”, CAV
`Cisplatin
`
`Carboplatin‘, gemcitabine‘, vinorelbine‘, docetaxel
`Vinorelbine‘
`
`Gemcitabinelcisplatin, gemcitabine/epirubicin
`Gemcitabine
`Taxanes
`
`T c-Kit
`T PC cell-derived growth factor
`T Survivin
`T P2lWAF1/CIPl
`
`Cisplatin + etoposide
`Platinum regimens
`Cisplatin/etoposide
`Platinum regimens
`
`Altered cell cycling
`T RB
`T p27Kip1
`J, Cyclin B]
`T 14-3-30
`
`1 Eg5
`
`Cisplatin regimens“
`Cisplatin regimens“
`Platinums + antimitotic agents
`Cisplatin + gemcitabine
`Cisplatin + antimitotic agent
`
`(continued)
`
`

`
`340
`
`Table 4 (continued)
`Factor
`
`Agents affected
`
`“Data were equivocal or negative in some individual trials
`"Effect clinically was opposite from preclinical effect
`“Paradoxical increase in efficacy in p53 IHC positive patients in occasional studies
`“Celecoxib improved outcome in patients whose tumors expressed COX-2
`‘Trend present
`
`D.J. Stewart
`
`Table 5 Factors for which available clinical data fail to strongly support a role in lung cancer
`resistance despite a role in preclinical resistance
`Factor
`
`Agents assessed
`
`Tumor blood flow/HIF-loL/
`VEGF
`
`1 Lung resistance protein
`1 Glutathione-S-transferase-1:
`1 Nucleotide excision repair
`(ERCC1)
`T Ribonucleotide reductase M1
`1 Rad51 (homologous
`recombination repair)
`1 BRCA1
`T FANCD2
`Mutant p53
`1 Epidermal growth factor receptor
`by IHC or FISH“
`T HER-2/neu (erbB-2, p185)
`L p-ERK
`T p-AKT
`K-ras mutations
`
`T PKC-or
`1 Bcl-2
`
`T Bcl-XL
`1 Bak, Bad, Bid
`1 Bax
`
`Cisplatin combinations
`
`Taxanes, CAV, some cisplatin regimens
`Vinorelbine regimens, some platinum regimens
`Gemcitabine/docetaxel, gemcitabinelepirubicin
`
`Platinum + etoposide
`Cisplatin + gemcitabine
`
`Gemcitabine + epirubicin
`Platinum regimens
`Taxanes or vincas without platinums
`Platinums, taxane, gemcitabine, vinorelbine, radiation
`
`Platinum regimens”
`Platinum regimens, taxane regimens
`Platinum regimens, taxanes
`Platinum regimens“
`Cisplatin + gemcitabine
`Platinum regimens (multiple), vincas, taxanes, etoposide
`regimens
`Vinorelbine
`Vinorelbine
`
`Cisplatin regimens, Vinorelbine/docetaxel
`
`“Patients with EGFR mutations, particularly with exon 19 deletions did benefit more from
`chemotherapy than did patients with EGFR wild type tumors in some studies
`
`“Data are equivocal or not consistent across all clinical studies
`
`Drug Uptake
`
`Tumor uptake of drugs may be by passive diffusion, by active transport or by both.
`Mechanisms of cellular uptake of taxanes and vinca alkaloids in lung cancer cells
`are uncertain. For cisplatin, reduced uptake has been reported in a high proportion
`
`

`
`Lung Cancer Resistance to Chemotherapy
`
`341
`
`of resistantNSCLC— cell lines. Reduced cisplatin uptake
`may be accompanied by membrane changes that might alter either passive diffusion
`or membrane transporter activity. Membrane changes include increases in rigidity
`
`2 density of lipid packingf-ngomyelin content. and decreased
`
`long chain and unsaturated fa
`Incorporation of exogenous long chain
`fatty acids into membrane phospholipids augmented cisplatin uptake and reduced
`resistance 2
`Cisplatin-resistant lung cancer cell lines may have reduced expression of the
`copper/platinum uptake transporter CTR1 I Platinum-resistant cells may also
`have broad cross-resistance and decreased expression of a wide spectrum of mem-
`brane transporters : and conversely, exposure to many types of chemotherapy
`and targeted agents could potentially render tumors cross-resistant to platinums
`through temporary downregulation of CTR1 expression‘
`Na’', K’' ATPase may also be important in cisplatin uptake and efficacy in lung
`
`cancer cell lines, particularly with NSCLC !The Na’', K’' ATPase antago-
`
`ecrease cisplatin uptake and
`nists thromboxane A2 ‘ and sorbit
`efficacy, and the antagonism of N’', K’' ATPase by the glucose metabolite sorbitol
`could potentially augment cisplatin resistance in poorly controlled diabetes
`Thallium-201 (T201) retention on SPECT scanning may reflect Na’', K’' ATPase
`activity. In clinical trials, pretreatment tumor T201 retention predicted outcome
`
`with chemotherapy in one SCLC iut did not correlate in another SCLC
`
`unknown if the lack of correlation is
`study - nor in a NSCLC study
`due to a lack of importance clinically of N’', K’' ATPase, to an inaccurate prediction
`of N", K" ATPase by T201 retention, or to a modifying effect on outcome by the
`agents used in combination with cisplatin.
`With respect to other agents, etoposide uptake into resistant NSCLC tumor
`cells is lower than uptake into sensitive SCLC tumor cells _ It is not known
`how etoposide enters lung cancer cells, but detergents that may increase
`membrane fluidity increased etoposide efficacy in NSCLC cell lines - while
`increased cellular content of cholesterol (which increases cell membrane rigidity)
`
`augmented resistance
`
`Human equilibrati
`uptake of gemcitabin
`abine resistance
`
`clinical studies
`
`
`
`leoside transporter 1 (hENT1) plays a role in cellular
`, and hENT1 deficiency was associated with gemcit-
`paiticularly with intrinsic resistance- While some
`a role for hENT1 in NSCLC resistance to gemcitabine
`
`- others did
`Overall, preclinical data suggest that reduced drug uptake may be an important
`cause of resistance in lung cancer, but clinical data are very limited.
`
`Drug Efflux
`
`Efflux pumps may also render cells resistant by pumping drugs out of cells after
`they enter.
`
`

`
`342
`
`D.J. Stewart
`
`Multidrug Resistance Protein
`
`NSCLC cell lines tend to have greater expression of multidrug resistance protein
`(MRP) (which may function as a glutathione S-conjugate (GS-X) pump‘ than
`do SCLC cell lines
`MRP expression was associated with decreased accu-
`
`
`
`mulation ofcisplat-aclitaxel,jandother agentsIin lungcancercell
`
`
`
`and
`ma be associated with
`
`lines. Protein or mRNA expression of MRP in SCLC
`NSCLC ‘cell lines or heterotrans lants
`resistance to anthracyclines
`vinca
`etoposide_, taxan
`tabine,
`although an association with resistance has not been seen in all cell lines or with all
`drugs
`(particularly for cisplatin
`d gemcitabine -).
`
`
`
`
`MRP1_ and MRP7may beEimportant. Impact of
`
`MRP on resistance may be decreased by 5-fluoro
`‘or by glutathione depletion‘.
`Clinically, MRP expression is common in both NSCLC‘ and SCLC
`2 and MRP expression increased after exposure to platinum-based regimens‘
`suggesting that it may be upregulated as a protective response. High MRP expression
`was associated with decreased respo
`or survival-
`
`
`
`eiving platinum-based
`Outcome in
`or with vindesine plus etoposide
`combina
`
`advanced NSCLC patients treated with cisplatin plus irinotecan also varied signifi-
`
`in SCLC:CLC
`
`
`
`cantly with MRP2 host gem“ However, no correlation was seen between
`MRP expression and response
`r survival: with platinum-based combina-
`tions in some other NSCLC studies, and impact of MRP expression on clinical out-
`come may be greater in adenocarcinomas than in squamous cell carcinomas-
`Overall, the available data suggest that MRP may play a role in resistance in
`lung cancer.
`
`MDRI/p-Glycoprotein
`
`In SCLC—and NSCLC— cell lines, increased IHC expression
`of the efflux pump p-glycoprotein (P-gp) or increased mRNA expression for its
`
`gene MDRI was associated with increased resistance to anthracycl'
`vinca alkaloids—, etoposid
`es
`was not usually associated with the up
`sistance to
`platinums (which may inhibit P-gp
`actually sensitize cells to
`
`
`
`P-gp expression was occasionally associated with MDR1 gene amplification
`
`
`and tumor samplei
`gemcitabine- In lung cancer cell
`correlated with hypoxia‘or with expression ofH]F-lU.-or caveolin 1
`
`32 in NSCLC
`
`
`
`- Expression of the gap junction protein and tumor supp
`cells downregulated MDRI and sensitized cells to vinorelb
`
`(5-FU), by veraparnil,
`
`

`
`Lung Cancer Resistance to Chemotherapy
`
`343
`
`Clinically, MDR1 mRNA or P-gp was expressed in 11-32% of NSCLC tumor
`samples - and in 13-60% of SCLC tumor sam
`Expression increased after chemotherapy treatment—
`cal studies‘and in some NSCLC clini
`2 high tumor MDR1 or P-gp expression was significantly associated with
`
`decreased mend/or survival:
`
`in patients treated with chemotherapy, including cisplatin—etoposid
`_, paclitaxel plus a platinum_, cyclophosphamide—doxorubicin—
`vincristine (CAV)- or other doxorubicin or etoposide regimens2
`However, in other NSCLC trials, tumor P-gp expression did not correlate signifi-
`cantly with response to a variety of platinum-based regimens
`that also included vinca al
`irinotec
`
`gemcitabine ‘or radiafio
`
`In pharrnacogenetic studies, the MDR1 3435 CC host genotype was associated
`with significantly better response to cisplatin—etoposide- and cisplatin—vinorelbine
` patients than were other genotypes, but was not
`associated with the outcome in NSCLC patients treated with cisplatin—docetaxel—
`High tumor expression of MDRI/P-gp or MRP was associated with reduced
`uptake or retention of Tc-99m methoxyisobutyl isonitrile (MIBI) and technetium-
`99m tetrofosmin (Tc-TF) on SPECT scarming in some studies—
`
`
`
`but not in othe-‘Tumor MIBI uptake was significantly lower in NSCLC
`
`
`
`than in SCLC C— and NSCLC:
`clinical trials, there was a significant correlation between tumor
`uptake/reten-
`
`tion on SPECT and response to cisplatin—etoposide-based regimens
`
`
`
`or there
`
`taxel-based regimens
`
`NSCLC and SCLC patients was
`
`— to cisplatin, mitomycin-C plus vindesine-to pacli-
`
`or to other nonplatinum regi
`was atrendtowardm e smallMIBI studyincludingboth
`tor receptor (EGFR) inhibitor gefitinil:-ted chemotherapy uptak
`or e
`P-gp expressing lung cancer cell lines‘ and
`grafts
`ornized lung cancer clinical trials, neither verapamil
`
`
`
`.
`
`The calcium channel blocker verap
`
`and the epidermal growth fac-
`
`
`
`nor the hormonal agent/P-gp antagonist megestrol acetate
`nor g
`2 improved outcome when added to chemotherapy.
`Overall, available evidence suggests that MDR1/P-gp is associated with resis-
`tance to some chemotherapy agents in SCLC, and much (but not all) of the avail-
`able evidence also suggests a role for MDR1/P-gp in resistance in NSCLC.
`
`Breast Cancer Resistance Protein
`
`High tumor 11-IC expression-and blood concentrations 2 of the efflux
`transporter breast cancer resistance protein (BCRP) were associated with lower
`
`

`
`344
`
`D.J. Stewart
`
`response rates— and shorter survival - in NSCLC patients receiving
`platinum-based chemotherapy.
`
`Ral-Interacting Protein (RLIP76) (RALBP1)
`
`With vinorelbine 2 and doxorubicin‘ increased efflux, decreased
`cellular concentrations and resistance in SCLC and NSCLC cell lines was seen with
`
`the transport
`overexpression of the glutathione-conjugate transporter RLIP76,
`activity of which is regulated by protein kinase C (PKC)-ct-mediated phosphoryla-
`tion -. The differential phosphorylation of RLIP76 in NSCLC vs. SCLC may
`contribute to the greater resistance to doxorubicin in NSCLC cells-
`
`Lung Resistance Protein
`
`Lung resistance protein (LRP) expression correlated with resistance to cisplatin
` n some NSCLC cell lines, but in other NSCLC cell
`lines, LRP expression did not correlate with resistance to cisplatin
`etopo-
`
`
`
`sidi anthracyclines
`
`cin
`
`e irinotecan metabolite SN-38
`
`. In some clinical studies,
`
`, bleomy-
`
`NSCLC response to platinum-based chemotherapy was decreased in patients whose
`tumors expressed LRP-, while there was no significant link between
`efficacy and LRP expression in other NSCLC
`d SCLC-
`studies usin
`latinurns combined with tax
`epipodoph llotoxins
`
`if or using taxane-based che
`, or CAV
`Exposure to platinums did not upregulate expression of LRP - Overall, LRP
`does not appear to play a major role in lung cancer resistance.
`
`P-Type Adenosine Triphosphatase (ATP 7B)
`
`In NSCLC xenografts, cisplatin resistance correlated with expression of the copper
`transporter ATP 7B which may play a role in cisplatin efflux I
`
`Drug Detoxification
`
`Glutathione (GSH)
`
`GSH may bind and inactivate cisplatin, augment repair of platinum—DNA adducts
`I and potentiate drug efflux via GS-X pumps (including MRP
`In
`Nscm—ce111ines»
`esn
`
`

`
`Lung Cancer Resistance to Chemotherapy
`
`345
`
`content was associated with resistance to cisplatin—(with
`reduced platinum—DNA
`and reduced intracellular platinum accu-
`mulation
`oside
`yclines
`'nca alkaloids
`,
`
`
`camptoth
`mito
`latin
`, methotrexa
`,
`and radia
`However, there were also examples where GSH content did not
`correlate with cisplatin resistance in NSCLC cell lines- NSCLC xenografts
`2, or SCLC cell lines
`or did not correlate with resistance to anthra-
`cyclines (-ophyllotox
`vinca alkaloids
`
`
`
`
`the glutamate-cysteine ligase/gamma-
`Expressi
`or activity
`
`glutamylcysteine synthetase gene responsible for GSH synthesis correlated with
`cisplatin resistance, and expression of this gene was higher in NSCLC than in
`SCLC 2. The enzymes GSH peroxidase and GSH reductase also may play a
`role in cisplatin resistance‘
`While results vary across cell lines, the bulk of available preclinical evidence
`suggests that GSH may play a role in resistance to cisplatin and perhaps other
`agents. Clinical data in lung cancer remain limited.
`
`Glutathione-S- Transferase-pi
`
`The binding of GSH to drugs may be catalyzed by GST and the expression of the
`GST isoenzyme glutathione-S-transferase-pi (GSTn:) was higher in NSCLC than in
`SCLC cell lines— As with GSH, the association between GST and che-
`motherapy resistance varied across studies. GST inhibitors increased sensitivity to
`cisplatin—, and cisplatin resistance correlated with