MET overexpression as a hallmark of the epithelial-mesenchymal transition (EMT) phenotype in colorectal cancer

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Background: Dysregulation of the proto-oncogene MET (mesenchymal-epithelial transition factor gene) has been implicated in tumorigenesis and correlates with worse survival and chemo/radio-resistance in colorectal cancer (CRC). EMT has been identified as a dominant molecular characteristic of a subset of CRC tumors and represents a key feature in the developing colorectal taxonomy. The purpose of this study was to compare protein expression of MET with protein/gene expression of EMT markers and other clinicopathological characteristics, and to evaluate its impact on overall survival (OS). Methods: We performed an exploratory analysis of 590 CRC samples using data from The Cancer Genome Atlas. Fisher-exact test and Pearson’s method was used to determine the relationship between MET protein expression, clinicopathological characteristics and EMT marker protein expression by reverse-phase protein array (RPPA) and EMT-associated gene expression by RNA-sequencing. Regression tree method was applied to find the best cutoff point for MET using patients with available survival data. Overall survival (OS) was estimated non-parametrically using Kaplan-Meier curve and log-rank test was used to evaluate hazard ratio. Results: MET expression by RPPA did not correlate with traditional clinicopathologic characteristics. MET was overexpressed in 17% of CRC tumors and was significantly associated with OS (HR 2.92; 95% CI: 1.45 - 5.92). Correlation analysis of MET levels with gene expression of EMT markers AXL, CDH1, FGFR1, SNAIL, TWIST1/2, VIM, SLUG, ZEB1/2, FN1 demonstrated that the highest quartile of MET protein expression was associated with a 1.5 fold increase in ZEB1 (p = 0.002), a 1.4 fold increase in AXL (p = 0.005) and ZEB2 (p = 0.008), and a 1.3 fold increase in VIM (p = 0.02). MET expression also correlated strongly with protein expressions of SNAIL (transcription factor for EMT) (r = 0.96) and ERCC1 (r = 0.83) (a marker for oxaliplatin chemo-resistance). Conclusions: Increased MET protein expression is seen in 17% of CRC tumors and strongly correlates with a molecular EMT phenotype and poor survival in patients with CRC. MET protein expression may be a surrogate biomarker for this unique subset of CRC.

Role of the MET–HGF axis in colorectal cancer: precepts and prospects

SUMMARY Colorectal cancer (CRC) accounts for 10% of all cancer-related mortality globally. Despite significant therapeutic advances, overall survival is limited. The restricted repertoire of therapies necessitates investigation into novel pathways of colorectal carcinogenesis. The proto-oncogene MET encodes a receptor tyrosine kinase that acts as a receptor for the HGF. Dysregulation of this MET–HGF axis has been implicated in proliferation, survival and metastasis in various tumor types including CRC. Increased MET–HGF expression correlates with tumor progression and adverse survival outcome. The prognostic impact argues in favor of employing inhibition of the MET–HGF axis as a promising new therapeutic strategy. Future investigations should endeavor to assess the potential application of targeted MET–HGF therapy in CRC and towards patient selection.

Effect of bevacizumab on rate of oxaliplatin-induced thrombocytopenia and splenomegaly

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Background: Oxaliplatin-based chemotherapy can cause hepatic sinusoidal injury (HSI) leading to portal hypertension. This results in splenic sequestration of platelets and thrombocytopenia. Evidence suggests that bevacizumab may protect against HSI, although the clinical impact of this has not been well examined. The purpose of our study was to evaluate rate of thrombocytopenia and splenomegaly as clinical end-points indicative of bevacizumab mediated modulation of oxaliplatin-induced hepatic toxicity. Methods: We performed a retrospective review of metastatic colorectal cancer patients treated at M D Anderson Cancer Center from 1/2003 to 1/2010 with ≥ 3 months of frontline fluoropyrimidine and oxaliplatin (FOLFOX) with or without bevacizumab. Patients with prior liver disease, liver surgery or absence of spleen were excluded. Splenic volumes pre, during and post FOLFOX therapy were determined with CT scans and correlated with platelet counts and treatment. Results: A total of 184 patients [Bev cohort: FOLFOX/Bev (n =138); Non-Bev cohort: FOLFOX alone (n = 46)] were identified. Baseline characteristics (age, gender, spleen size and platelet counts) were similar in both groups. Median number of oxaliplatin cycles for each cohort was 9.00 (p = 0.9). The median total oxaliplatin dose did not differ between the two cohorts (p = 0.9). Development of splenomegaly (volume increase ≥ 30%) was more common in the Non-Bev cohort (48% vs. 32%; p = 0.013). The median time to develop splenomegaly was significantly longer in the Bev cohort (7.6 vs. 5.5 months; p = 0.023). Splenomegaly correlated with a higher rate of thrombocytopenia (defined as platelets < 150K) at 3 months (40% vs. 16%, p = 0.0005) and beyond (during 3 to 6 months of treatment, p < 0.0001). Correspondingly, bevacizumab therapy was associated with lower rates of thrombocytopenia at 3 months (24% in Bev cohort vs. 43% in Non-Bev cohort, p = 0.006) and beyond (p = 0.003). Conclusions: In our cohort, addition of bevacizumab to oxaliplatin chemotherapy reduces the occurrence of splenic enlargement, which correlates with a decreased rate of thrombocytopenia. Further studies to understand the potential hepato-protective mechanism of anti-VEGF therapy are needed.

Prognostic and predictive effect of COX-2 expression in appendiceal adenocarcinomas

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Background: Cyclooxygenase-2 (COX-2), an inducible isoenzyme, is upregulated in inflammation and involved in cancer progression by promoting angiogenesis, cell proliferation and migration and by inhibiting apoptosis. COX-2 is implicated in colorectal tumorigenesis and by extension COX-2 expression testing and therapeutic inhibition has been considered in appendiceal adenocarcinomas (AAs). However, its role in this setting has never been well studied. The purpose of our study was to investigate COX-2 expression in AAs and to evaluate its prognostic and predictive significance.

Methods: We performed a retrospective review of 607 patients with AAs treated at MD Anderson Cancer Center between 2002 and 2010. Immunohistochemistry was performed for COX-2 expression (COX2 mAb Clone CX229, Cayman Chemical) in 49 (8%) patients. Thirty (61%) stained positive and 19 (39%) showed no staining. Kaplan-Meier product limit method and log-rank test were used to estimate overall survival (OS) and to determine association between OS, COX-2 expression and other characteristics.

Results: Median age at diagnosis was 47 yrs (range 34-78 yrs). Grade (P = 0.003), completeness of cytoreduction score (P = 0.010) and stage (P = 0.023) were significantly associated with OS. Median OS for patients with COX-2 positive and COX-2 negative tumors was 58.3 and 42.8 months, respectively (P = 0.232). Nine COX-2 positive patients received celecoxib (selective COX-2 inhibitor) in combination with other chemotherapy. Mean treatment duration was 5.5 months with best radiographic response being stable disease in 7 patients. Reduction in tumor markers (CEA or CA19-9) was seen in 7 cases (median reduction of 30%). Similar treatment duration (6.6 months), rate of stable disease (6/8 pts) and tumor marker reduction (7/8 pts) was seen on the preceding non-celecoxib containing chemotherapy in these patients. Median OS, with and without COX-2 inhibition, was 55.7 and 57.6 months respectively (P = 0.57).

Conclusions: In this cohort, COX-2 expression is not a significant prognostic factor in AAs. Benefit from COX-2 inhibition in COX-2 expressing AAs is unclear. Current data does not support the routine use of either COX-2 testing or COX-2 inhibition therapy in AAs.

Motesanib and advanced NSCLC: experiences and expectations

INTRODUCTION

Benefits from conventional chemotherapy in NSCLC have plateaued. Accordingly, sizeable efforts have gone into developing novel therapies. Tumor angiogenesis mediated principally by VEGF has emerged as an alluring target because of its vital role in tumor growth, sustenance and metastasis. The Eastern Cooperative Oncology Group (ECOG) trial E4599 showed significant improvement in overall survival with addition of bevacizumab, a VEGF monoclonal antibody, to cytotoxic chemotherapy in metastatic NSCLC. A number of compounds targeting tumor angiogenesis have since gone into preclinical and clinical testing. The multifaceted nature of cancer has led to development of multitarget tyrosine kinase inhibitors (MTKIs) that target several pathways concomitantly. Motesanib, an orally administered potent small molecule, targets VEGFR 1 - 3, PDGFR and KIT. Oral bioavailability and preliminary evidence of activity make this compound an appealing choice for additional investigations.

AREAS COVERED

This review summarizes the background of angiogenesis and rationale for targeting the VEGF pathway in NSCLC. The authors also review recent clinical trial data evaluating motesanib.

EXPERT OPINION

VEGF is a validated target in NSCLC. In early trials motesanib has shown promising activity in NSCLC with tolerable toxicity profile. A Phase III trial with motesanib in combination with chemotherapy is ongoing.

A review of electrocardiography in pulmonary embolism: recognizing pulmonary embolus masquerading as ST-elevation myocardial infarction

A 64-year-old woman with hypertension and diabetes presented with acute shortness of breath and left-sides chest discomfort. Electrocardiopgram (ECG) demonstrated Q waves, coved ST-segment elevations, and T-wave inversions in leads V₁-V₄, suggesting acute anterior ST-elevation myocardial infarction (STEMI). catheterization revealed nonocclusive coronary artery disease with elevated pulmonary and right heart pressures, confirmed by echocardiography. Ventilation perfusion scan was deemed high probability for pulmonary embolism (PE). Treatment for a submassive PE was initiated and ECG changes resolved by discharge. This case exemplifies similarities in clinical presentation of PE and acute STEMI. The presence of Q waves in anterior leads wih coved ST-elevation after PE has not been described previously. We review the differential diagnosis of ST elevation and the assorted spectrum of ECG changes seen in PE.