Molecular events in gastric cancer

Molecular events in gastric cancer Lorenzo Fornaro, MD Unit of Medical Oncology 2 Azienda Ospedaliero-Universitaria Pisana Istituto Toscano Tumori Pisa- Italy

Disclosures No conflict of interest to disclose

Disclosures Education: Medical Oncologist Apologies to: Geneticists, Molecular biologists, Pathologists and many others

Agenda Molecular profiling for clinicians: something more than the essential Key molecular alterations: clinical perspective Familial gastric cancer: overview Conclusions

Moving from pathology Diffuse type Intestinal type

Revisiting pathology: clinical perspectives Shah MA et al. Clin Cancer Res 2011

Revisiting pathology: clinical perspectives Bittoni A et al. PLoS One 2013

From pathology to genetics: molecular subtypes Gene expression profiling for 37 gastric cancer cell lines Two major intrinsic subtypes identified (171 gene set): Genomic-Intestinal vs. Genomic-Diffuse Concordance between genomic (G-INT and G-DIF) and pathological (INT and DIF) findings: 64% Tan IB et al. Gastroenterology 2011

From pathology to genetics: molecular subtypes Mesenchymal Proliferative Metabolic Diffuse vs. Intestinal vs. Mixed 58.2% - 29.2% - 11.9% 17.3% - 73.6% - 9.1% 40.6% - 53.6% - 5.8% Pathway activation EMT, TGFβ, VEGF, NF-κB, mtor, SHH, CSC E2F, MYC, and RAS Amplified genes - CCNE1, MYC, ERBB2, KRAS SPEM Methyled CpGs, hyper vs. hypo 84.6% - 15.4% 57.8% - 42.2% 76.1% - 23.9% TP53 mutations low high low Lei Z et al. Gastroenterology 2013 -

Ready for clinical application? Tan IB et al. Gastroenterology 2011

Ready for clinical application? Lei Z et al. Gastroenterology 2013

TCGA: molecular subgroups 50% 9% 22% 20% Cancer Genome Atlas Research Network. Nature 2014

TCGA: limitations Limited follow up for the examined patients limitations in the interpretation of the prognostic role No clear distinction of different driver molecular alterations among different subgroups anticipated limited role in the prediction of benefit from targeted agents Subgroups evaluated on resected specimens different prevalence of subgroups between localized and advanced settings

Agenda Molecular profiling for clinicians: something more than the essential Key molecular alterations: clinical perspective Familial gastric cancer: overview Conclusions

Looking at molecular events from the bedside... Key molecular events in gastric cancer might represent therapeutic targets for biologic agents might identify subtypes enriched for a specific target What we will talk about: MSI (and ATM) FGFR2, KRAS, BRAF, MET CSCs PD-1/PD-L1

MSI in gastric cancer Prevalence of MSI in gastric cancer ranges from 10% to 30% 1 heterogeneity due to the number of cases studied and the type and number of markers examined MSI-high is associated with defects of the mismatch repair pathway: loss of expression of hmlh1 or hmsh2 (gene promoter hypermethylation) MSI gastric cancer has peculiar clinical features Older age, Lauren s intestinal subtype, antral location 2 1Halling KC et al. Am J Pathol 1999 2Seo HM et al. J Surg Oncol 2009

ATM expression in gastric cancer Ataxia-telangiectasia mutated (ATM) gene plays a pivotal role in signaling and responding to double strand breaks (DSBs) Low ATM expression more frequently identified in patients: of older age in more advanced stage with MSI-positive tumor Kim JW et al. Int J Cancer 2014

ATM expression and MSI in gastric cancer Kim JW et al. Int J Cancer 2014

PARP-inhibitors in ATM low gastric cancer 124 patients progressed after I-line with evaluable ATM status by IHC R A N D O M I Z E TXL Olaparib q4w TXL Placebo Paclitaxel + Olaparib 61 patients 80 mg/m 2 IV, d1-8-15 100 mg bid OS, continuously Paclitaxel + Placebo 62 patients 80 mg/m 2 IV, d1-8-15 q4w Bang YJ et al. J Clin Oncol 2015

KRAS mutations in MSI-positive gastric cancer Low rate of BRAF mutation: 1/124 MSS cases and 0/37 MSI cases BRAF mutation not involved in gastric tumorigenesis Higher incidence of KRAS mutations within the MSI group the activation of KRAS-dependent pathways contributes to the tumorigenesis of gastric cancers with MMR deficiency Oliveira C et al. Oncogene 2004

FGFR2 amplification in gastric cancer FGFR2 amplification occurs in almost 10% of gastric cancer cases and is associated with higher FGFR2 expression 1 Dovitinib (TKI258): multitargeting oral TKI with potent inhibitory activity against bfgf receptors 1, 2, 3, VEGF receptors 1, 2, 3, PDGFR and c- KIT Dovitinib inhibits tumour growth in a human primary gastric cancer xenograft model bearing FGFR2 gene amplification 1 Failure of random phase II trial SHINE with AZD4547 vs. paclitaxel 2 1Deng N et al. Gut 2012; 2 Bang YJ et al.asco Ann Meeting 2015

MET in gastric cancer MET copy number alteration and over-expression reported in a variable number of gastric cancer cases 1 no standard methods for assessment Good correlation between gene number alteration by ISH and expression by IHC 2 IHC 0 IHC 2+ IHC 3+ disomy high polysomy gene amplification 1Peng Z et al. Plos One 2014 2Lee HE et al. Br J Cancer 2012

MET: negative prognostic role Peng Z et al. PLoS One 2014

MET and resistance to anti-egfr/her2 Patients with HER2+ esophago-gastric cancer treated for 10 days with lapatinib and then with XELOX + lapatinib. Endoscopic samples were taken for molecular analysis at: baseline including for ex vivo culture +/- lapatinib to predict in vivo response post-lapatinib monotherapy at surgery Significant correlation between the activation of MET with the level of P-Erk and P- PI3K:T-PI3K (total PI3K) ratio MET is likely to be a significant mechanism of lapatinib resistance in vivo De Silva N et al. Br J Cancer 2015

MET and gastric cancer: the end of the beginning? Study Arms (n) RR p PFS (mos) HR OS (mos) HR RILOMET-1 1 ECX + Placebo 39.2% 5.7 11.5 ECX + Rilotumumab 30% 0.027 5.7 1.30 9.6 1.37 METGastric 2 FOLFOX + Placebo 41% 6.8 11.3 FOLFOX + Onartuzumab 46% 0.253 6.7 0.90 11.0 0.82 1Cunningham D et al. ASCO Ann Meeting 2015 (abstr. 4000) 2Shah MA et al. ASCO Ann Meeting 2015 (abstr. 4012)

Cancer stem cells hypothesis: tumour heterogeneity STOCHASTIC MODEL CSCs MODEL Reya T et al. Nature 2001

Cancer stem cells in resistance and progression ANTI-CSCs AGENTS CONVENTIONAL AGENTS Reya T et al. Nature 2001

Cancer stem cells in gastric cancer Markers Stemness features Tumour formation CD44+ yes yes yes CD44+ EpCam+ CD44+ CD54+ CD44+ CD24+ yes yes ne yes yes ne yes yes ne CD133+ yes ne ne ALDH1+ yes yes yes ne: not evaluated Selfrenewal CT/RTresistance Singh SR. Cancer Lett 2013 Mod. from Brungs D et al. J Gastroenterol 2015

Targeting cancer stem cells: phase Ib/II 46 patients progressed after I-line to III-line Pretreated with platinum + fluoro/ts inhibitor TXL BBI608 Paclitaxel + BBI608 80 mg/m 2 IV, d1-8-15 480-500 mg bid OS, continuously q4w BBI608: acts on CSCs through the inhibition of the Stat3 and Wnt/β-catenin pathways Previous lines (n) G3 adverse events RR DCR PFS (weeks) OS (weeks) I-line: 10 Vomiting: 10% Among 20 patients not pretreated with taxanes II-line: 16 Diarrhea: 7% 31% 75% 20.6 39.3 III-line: 20 Fatigue: 7% Among 26 patients who failed prior taxanes 11% 68% 12.6 33.1 Becerra C et al. ASCO Annual Meeting 2015

PD-1/PD-L1 in gastric cancer Expression of immune check points molecules (PD-L1 most studied) varies in gastric cancer higher expression in cancer than in healthy stomach correlated with poor clinico-pathologic features in the advanced setting vs. lower stage/ intestinal type/well-moderately differentiated tumors in radically resected specimens Further studies needed to clarify the prognostic role poor prognosis in the metastatic setting vs. good prognosis in the adjuvant setting Abdel-Rahman O. Crit Rev Oncol Hematol 2015

PD-L1 negative prognostic role: meta-analysis PD-L1 expression and 3-year OS PD-L1 expression and 5-year OS Wu P et al. Plos One 2015

Immune checkpoints: CTLA4 and PD-1/PD-L1 Pardoll DM. Nat Rev Cancer 2012

PD-1 blockade and MMR status Le DT et al. N Engl J Med 2015

Phase Ib KEYNOTE-012 39 patients Pembrolizumab ECOG PS 0-1 Measurable disease RECIST v.1.1 Pembrolizumab 10 mg/kg IV PD-L1 expression in 1% tumor cells q2w Pembrolizumab shows signals of activity in gastric cancer RR: 22% (median duration of response: 40 weeks) 6-months PFS rate: 26% 6-months OS rate: 66% Further studies needed to confirm the value of anti-pd-1 agents KEYNOTE-062: I-line, Pembrolizumab vs. CT+Pembrolizumab vs. CT KEYNOTE-061: II-line, Pembrolizumab vs. Paclitaxel Bang YJ et al. WCGIC 2015 (LBA-04)

Rationale for anti-pd-1/pd-l1 Higher mutation burden higher neoantigen load greater benefit from PD-1 blockade in NSCLC Rizvi NA et al. Science 2015

Rationale for anti-pd-1/pd-l1 Higher mutation burden higher neoantigen load greater benefit from PD-1 blockade in NSCLC Rizvi NA et al. Science 2015 Lawrence MS et al. Nature 2013

Agenda Molecular profiling for clinicians: something more than the essential Key molecular alterations: clinical perspective Familial gastric cancer: overview Conclusions

Familial gastric cancer Three main syndromes identified hereditary diffuse gastric cancer gastric adenocarcinoma and proximal polyposis of the stomach familial intestinal gastric cancer Gastric cancer risk increased among other cancer-associated syndromes (e.g. Lynch, Li- Fraumeni, Peutz-Jeghers, and others) Only hereditary diffuse gastric cancer syndrome is genetically explained mutations in CDH1, encoding E-cadherin mutations in CTNNA1, encoding alpha-e-catenin Oliveira C et al. Lancet Oncol 2015

HDGF: role of E-cadherin Corso G et al. Cancer Metastasis Rev 2014

HDGC: second-hit CDH1 inactivation Oliveira C et al. Lancet Oncol 2015

HDGC: clinical features Oliveira C et al. Lancet Oncol 2015

HDGC: management algorithm Tan RY and Ngeow J. World J Gastrointest Oncol 2015

Agenda Molecular profiling for clinicians: something more than the essential Key molecular alterations: clinical perspective Familial gastric cancer: overview Conclusions

Conclusions The knowledge of the molecular basis of gastric cancer is rapidly evolving Different classifications (TCGA and others) proposed Prognostic/predictive value: to be investigated and validated Mind possibile overlap among different classifications Multiple potential therapeutic targets identified Immune checkpoints inhibitors particularly intriguing Potential mechanisms of resistance to targeted agents suggested e.g. MET for anti-her2/anti-egfr agents

Conclusions Be aware of gastric cancer-associated syndromes Be aware of the gastric cancer risk associated with other cancer-related syndromes Insights into the molecular basis and pathogenesis of gastric cancer Genetic screening for suspected cases and their relatives dedicated genetic teams needed shared and validated algorithms of surveillance and treatment

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