Edwin A. Clark

Expression of Epiregulin and Amphiregulin and K-ras Mutation Status Predict Disease Control in Metastatic Colorectal Cancer Patients Treated With Cetuximab

PURPOSE The antiepidermal growth factor receptor (EGFR) antibody cetuximab shows activity in multiple epithelial tumor types; however, responses are seen in only a subset of patients. This study was conducted to identify markers that are associated with disease control in patients treated with cetuximab. PATIENTS AND METHODS One hundred ten patients with metastatic colorectal cancer were enrolled onto a cetuximab monotherapy trial. Transcriptional profiling was conducted on RNA from mandatory pretreatment metastatic biopsies to identify genes whose expression correlates with best clinical responses. EGFR and K-ras mutation analyses and EGFR gene copy number analyses were performed on DNA from pretreatment biopsies. RESULTS Gene expression profiles showed that patients with tumors that express high levels of the EGFR ligands epiregulin and amphiregulin are more likely to have disease control with cetuximab (EREG, P = .000015; AREG, P = .000025). Additionally, patients whose tumors do not have K-ras mutations have a significantly higher disease control rate than patients with K-ras mutations (P = .0003). Furthermore, patients with tumors that have high expression of EREG or AREG also have significantly longer progression-free survival (PFS) than patients with low expression (EREG: P = .0002, hazard ratio [HR] = 0.47, and median PFS, 103.5 v 57 days, respectively; AREG: P < .0001, HR = 0.44, and median PFS, 115.5 v 57 days, respectively). CONCLUSION Patients with tumors that have high gene expression levels of epiregulin and amphiregulin and patients with wild-type K-ras are more likely to have disease control on cetuximab treatment. The identified markers could be developed further to select patients for cetuximab therapy.

The Mechanisms of Differential Sensitivity to an Insulin-like Growth Factor-1 Receptor Inhibitor (BMS-536924) and Rationale for Combining with EGFR/HER2 Inhibitors

Overexpression and enhanced activity of insulin-like growth factor-I receptor (IGF-IR) in diverse tumor types make it an attractive target for cancer therapy. BMS-536924 is a potent small molecule inhibitor of IGF-IR, which shows antitumor activity in multiple tumor models, including sarcoma. To facilitate the development of IGF-IR inhibitors as cancer therapy, identification of biomarkers for selecting patients most likely to derive clinical benefit is needed. To do so, 28 sarcoma and neuroblastoma cell lines were screened for in vitro response to BMS-536924 to identify sensitive and resistant cell lines. Notably, Ewings sarcoma, rhabdomyosarcoma, and neuroblastoma are more responsive to BMS-536924, suggesting these specific subtypes may represent potential targeted patient subpopulations for the IGF-IR inhibitor. Gene expression and protein profiling were performed on these cell lines, and candidate biomarkers correlating with intrinsic and/or acquired resistance to BMS-536924 were identified. IGF-I, IGF-II, and IGF-IR were highly expressed in sensitive cell lines, whereas IGFBP-3 and IGFBP-6 were highly expressed in resistant lines. Overexpression of epidermal growth factor receptor (EGFR) and its ligands in resistant cell lines may represent one possible resistance mechanism by the adaptation of IGF-IR-independent growth using alternative signaling pathways. Based on cross-talk between IGF-IR and EGFR pathways, combination studies to target both pathways were performed, and enhanced inhibitory activities were observed. These results provide a strategy for testing combinations of IGF-IR inhibitors with other targeted therapies in clinical studies to achieve improved patient outcomes. Further exploration of mechanisms for intrinsic and acquired drug resistance by these preclinical studies may lead to more rationally designed drugs that target multiple pathways for enhanced antitumor efficacy.

Phase II Genomics Study of Ixabepilone as Neoadjuvant Treatment for Breast Cancer

PURPOSE This phase II study evaluated the efficacy and safety of ixabepilone as neoadjuvant therapy for invasive breast cancer not amenable to breast conservation surgery. Gene expression studies were undertaken using genes that were identified as potentially associated with sensitivity/resistance to ixabepilone in prior preclinical investigations. PATIENTS AND METHODS Patients with invasive breast cancer >or= 3 cm were eligible. Ixabepilone 40 mg/m(2) was administered as a 3-hour intravenous infusion on day 1 of a 21-day cycle for four or fewer cycles. RESULTS One hundred sixty-one patients were treated. The overall complete pathologic response (pCR) rate was 18% in breast and 29% in estrogen receptor (ER) -negative patients. Gene expression data were available for 134 patients. ER gene expression (ER1) was inversely related to pCR in breast and had a positive predictive value (PPV) of 37% and negative predictive value (NPV) of 92%. A 10-gene penalized logistic regression (PLR) model developed from 200 genes predictive of ixabepilone sensitivity in preclinical experiments included ER and tau and had higher PPV (45%) and comparable NPV (89%) to ER1. Grade 3 to 4 adverse events (AEs) were reported for 32% of patients. Except for neutropenia and leukopenia, all grade 3 to 4 AEs occurred in <or= 3% of patients. Reversible peripheral neuropathy was experienced by 3% of patients. CONCLUSION ER, microtubule-associated protein tau, and a 10-gene PLR model that included ER were identified as predictors of ixabepilone-induced pCR. RESULTS indicate an inverse relation between ER expression levels and ixabepilone sensitivity. Neoadjuvant ixabepilone demonstrated promising activity and a manageable safety profile in patients with invasive breast tumors.

Identification of potential biomarkers for measuring inhibition of Src kinase activity in colon cancer cells following treatment with dasatinib

Elevated levels of Src kinase expression have been found in a variety of human epithelial cancers. Most notably in colon cancer, elevated Src expression correlates with malignant potential and is also associated with metastatic disease. Dasatinib (BMS-354825) is a novel, orally active, multi-targeted kinase inhibitor that targets Src family kinases and is currently under clinical evaluation for the treatment of solid tumors. However, the effects of dasatinib on epithelial tumors are not fully understood. We show that concentrations of dasatinib that inhibit Src activity do not inhibit proliferation in 10 of 12 colon cancer cells lines. However, inhibition of integrin-dependent adhesion and migration by dasatinib correlated with inhibition of Src activity, suggesting that dasatinib may have anti-invasive or anti-metastatic activity and antiproliferative activity in epithelial tumors. Using phospho-specific antibodies, we show that inhibition of Src activity in colon cancer cell lines correlates with reduced phosphorylation of focal adhesion kinase and paxillin on specific Src-dependent phosphorylation sites. We have validated the use of phospho-specific antibodies against Src Tyr419 and paxillin Tyr118 as biomarkers of dasatinib activity in vivo. Colon carcinoma–bearing mice treated with dasatinib showed a decrease in both phospho-Src Tyr419 and phospho-paxillin Tyr118 in peripheral blood mononuclear cells, which correlated with inhibition of Src activity in the colon tumors. Thus, peripheral blood mononuclear cells may provide a useful surrogate tissue for biomarker studies with dasatinib using inhibition of Src Tyr419 and paxillin Tyr118 phosphorylation as read-outs of Src activity. [Mol Cancer Ther 2006;5(12):3014–22]

Oncogenic NRAS has multiple effects on the malignant phenotype of human melanoma cells cultured in vitro

Activating mutations in the NRAS gene, which occur predominantly in codon 61 (Q61R, Q61K) are among the most common genetic events in malignant melanoma. NRAS protein with oncogenic codon 61 mutations may therefore be good therapeutic targets. In the present study, we used gene expression profiling as a method for global characterization of gene expression alterations that resulted from treatment of melanoma cells with siRNA specifically targeting NRASQ61R. Sixteen probe sets representing 15 unique genes were identified whose expression was significantly altered by siRNA against NRASQ61R in 2 melanoma cell lines. The genes with altered expression are involved in several functions, including modulation of cell growth, invasion and migration. The results suggest that downregulation of cyclin E2 and cyclin D1 and also upregulation of the negative cell‐cycle regulator HBP1 in NRASQ61R knockdown cells contribute to the inhibition of cell proliferation. Furthermore, suppression of oncogenic NRAS results in reduced migration and invasion, which is accompanied by downregulation of EphA2 (a receptor tyrosine kinase), uPAR (urokinase receptor) and cytoskeleton proteins such as leupaxin, paxillin and vinculin. These studies support the concept that suppression of oncogenic NRAS by siRNA can induce growth arrest and inhibit invasion of human melanoma cells by modulating the levels of these gene products.

Abstract 3571: Exploratory biomarker discovery for clinical development of ARQ 087, a potent pan-FGFR kinase inhibitor

Fibroblast growth factor receptor (FGFR) tyrosine kinase family members have gained increasing attention as potential therapeutic targets. Gene amplification, or gain-of-function translocations and mutations of these receptors, have been implicated in a variety of cancers including breast, gastric, bladder, ovarian, endometrial, lymphoma and myeloma. We have previously described the biological profiling of ARQ 087, a potent small-molecule pan-FGFR kinase inhibitor that shows anti-tumor activity in FGFR dysregulated tumor cells in vitro and in vivo. A number of cell lines with genetically-altered FGF receptors were identified that were sensitive in anti-proliferative assays to ARQ 087, including FGFR2 amplified gastric carcinoma lines KATO III and SNU-16, and endometrial lines AN3CA, MFE-296 and MFE-280 harboring FGFR2 mutants, as well as a breast cancer cell line with increased FGFR1 gene copy (MDA MB-157). Western blot pharmacodynamic analysis demonstrates that ARQ 087 inhibits FGFR phosphorylation and downstream pathway markers in these cell lines in a concentration-dependent manner. Using antibody arrays specific for known cytokines as well as regulatory proteins involved in angiogenesis and apoptosis, we have identified a number of protein biomarkers in cell lysates and in conditioned media of sensitive cell lines that changed in response to ARQ 087 exposure. Three proteins (cytochrome c, clusterin, and HTRA2) decreased in SNU-16 (ARQ 087-sensitive, FGFR amplified) but not DLD1 (ARQ 087-resistant, non FGFR expressing) cells. VEGF decreased and IL-1rα increased in SNU-16 but not in DLD1 conditioned media in response to ARQ 087. Furthermore, analysis of mouse plasma from animals bearing AN3CA tumors treated with ARQ 087 revealed a decrease in human VEGF, CXCL16, MMP-9, Serpin E1 and MIF and an increase in RANTES, IL-1β, IP-10, SDF-1, IL-1rα. TNFα, GM-CSF, IL-2, sTREM-1, sICAM-1, MIP-1β, IL-8. In summary, we have identified a number of cell lines from a broad cell line screening campaign that exhibited dysregulated FGFR pathway function and are sensitive to the anti-proliferative effects of ARQ 087. These cell lines, in turn, have been used as models in which to identify candidate biomarkers that may greatly facilitate subsequent clinical evaluation of this molecularly targeted anti-tumor agent. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3571. doi:10.1158/1538-7445.AM2011-3571