ERK-dependent IL-6 autocrine signaling mediates adaptive resistance to pan-PI3K inhibitor BKM120 in head and neck squamous cell carcinoma.

Hyperactivation of phosphatidylinositol 3-kinase (PI3K) pathway occurs frequently in head and neck squamous cell carcinoma (HNSCC). However, clinical outcomes of targeting the PI3K pathway have been underwhelming. In present study, we investigated the resistant mechanisms and potential combination therapeutic strategy to overcome adaptive resistance to PI3K inhibitor in HNSCC. Treatment of NVP-BKM120, a pan-PI3K inhibitor, led to upregulation of interleukin-6 (IL-6) and subsequent activation of either extracellular signal-regulated kinase (ERK) or signal transducers and activators of transcription 3 (STAT3), causing modest antitumor effects on the growth of HNSCC cells. Blockade of autocrine IL-6 signaling with siRNA or neutralizing antibody for IL-6 receptor (IL-6R) completely abolished NVP-BKM120-induced activation of ERK and STAT3 as well as expression of c-Myc oncogene, which resulted in enhanced sensitivity to NVP-BKM120. Moreover, when compared with a pharmacologic inhibitor or silencing of STAT3, trametinib, a MEK inhibitor, in combination with NVP-BKM120 yielded more potent anti-proliferative effects by inhibiting S phase transition, arresting cells at G0/G1 phase, and downregulating IL-6 and c-Myc expression. Furthermore, as compared with either agent alone, combination of NVP-BKM120 with trametinib or tocilizumab, a humanized anti-IL-6R antibody, significantly suppressed tumor growth in NVP-BKM120-resistant patient-derived tumor xenograft (PDTX) models, which was also confirmed in PDTX-derived cell lines. Collectively, these results suggested that IL-6/ERK signaling is closely involved in adaptive resistance of NVP-BKM120 in HNSCC cells, providing a rationale for a novel combination therapy to overcome resistance to PI3K inhibitors.

Co-clinical trials demonstrate predictive biomarkers for dovitinib, an FGFR inhibitor, in lung squamous cell carcinoma.

BACKGROUND: We conducted co-clinical trials in patient-derived xenograft (PDX) models to identify predictive biomarkers for the multikinase inhibitor dovitinib in lung squamous cell carcinoma (LSCC). METHODS: The PDX01-02 were established from LSCC patients enrolled in the phase II trial of dovitinib (NCT01861197) and PDX03-05 were established from LSCC patients receiving surgery. These five PDX tumors were subjected to in vivo test of dovitinib efficacy, whole exome sequencing and gene expression profiling. RESULTS: The PDX tumors recapitulate histopathological properties and maintain genomic characteristics of originating tumors. Concordant with clinical outcomes of the trial enrolled-LSCC patients, dovitinib produced substantial tumor regression in PDX-01 and PDX-05, whereas it resulted in tumor progression in PDX-02. PDX-03 and -04 also displayed poor antitumor efficacy to dovitinib. Mutational and genome-wide copy number profiles revealed no correlation between genomic alterations of FGFR1-3 and sensitivity to dovitinib. Of note, gene expression profiles revealed differentially expressed genes including FGF3 and FGF19 between PDX-01 and 05 and PDX-02-04. Pathway analysis identified two FGFR signaling-related gene sets, FGFR ligand binding/activation and SHC-mediated cascade pathway were substantially up-regulated in PDX-01 and 05, compared with PDX-02-04. The comparison of gene expression profiles between dovitinib-sensitive versus -resistant lung cancer cell lines in the Cancer Cell Line Encyclopedia database also found that transcriptional activation of 18 key signaling components in FGFR pathways can predict the sensitivity to dovitinib both in cell lines and PDX tumors. These results highlight FGFR pathway activation as a key molecular determinant for sensitivity to dovitinib. CONCLUSIONS: FGFR gene expression signatures are predictors for the response to dovitinib in LSCC.

Oncogenic BRAF fusions in mucosal melanomas activate the MAPK pathway and are sensitive to MEK/PI3K inhibition or MEK/CDK4/6 inhibition.

Despite remarkable progress in cutaneous melanoma genomic profiling, the mutational landscape of primary mucosal melanomas (PMM) remains unclear. Forty-six PMMs underwent targeted exome sequencing of 111 cancer-associated genes. Seventy-six somatic nonsynonymous mutations in 42 genes were observed, and recurrent mutations were noted on eight genes, including TP53 (13%), NRAS (13%), SNX31 (9%), NF1 (9%), KIT (7%) and APC (7%). Mitogen-activated protein kinase (MAPK; 37%), cell cycle (20%) and phosphatidylinositol 3-kinase (PI3K)-mTOR (15%) pathways were frequently mutated. We biologically characterized a novel ZNF767-BRAF fusion found in a vemurafenib-refractory respiratory tract PMM, from which cell line harboring ZNF767-BRAF fusion were established for further molecular analyses. In an independent data set, NFIC-BRAF fusion was identified in an oral PMM case and TMEM178B-BRAF fusion and DGKI-BRAF fusion were identified in two malignant melanomas with a low mutational burden (number of mutation per megabase, 0.8 and 4, respectively). Subsequent analyses revealed that the ZNF767-BRAF fusion protein promotes RAF dimerization and activation of the MAPK pathway. We next tested the in vitro and in vivo efficacy of vemurafenib, trametinib, BKM120 or LEE011 alone and in combination. Trametinib effectively inhibited tumor cell growth in vitro, but the combination of trametinib and BKM120 or LEE011 yielded more than additive anti-tumor effects both in vitro and in vivo in a melanoma cells harboring the BRAF fusion. In conclusion, BRAF fusions define a new molecular subset of PMM that can be targeted therapeutically by the combination of a MEK inhibitor with PI3K or cyclin-dependent kinase 4/6 inhibitors.

Activation of the Met kinase confers acquired drug resistance in FGFR-targeted lung cancer therapy.

Aberrant fibroblast growth factor receptor (FGFR) activation/expression is a common feature in lung cancer (LC). In this study, we evaluated the antitumor activity of and the mechanisms underlying acquired resistance to two potent selective FGFR inhibitors, AZD4547 and BAY116387, in LC cell lines. The antitumor activity of AZD4547 and BAY1163877 was screened in 24 LC cell lines, including 5 with FGFR1 amplification. Two cell lines containing FGFR1 amplifications, H1581 and DMS114, were sensitive to FGFR inhibitors (IC50<250 nm). Clones of FGFR1-amplified H1581 cells resistant to AZD4547 or BAY116387 (H1581AR and H1581BR cells, respectively) were established. Receptor tyrosine kinase (RTK) array and immunoblotting analyses showed strong overexpression and activation of Met in H1581AR/BR cells, compared with that in the parental cells. Gene set enrichment analysis against the Kyoto Encyclopedia of Genes and Genomes (KEGG) database showed that cytokine-cytokine receptor interaction pathways were significantly enriched in H1581AR/BR cells, with Met contributing significantly to the core enrichment. Genomic DNA quantitative PCR and fluorescent in situ hybridization analyses showed MET amplification in H1581AR, but not in H1581BR, cells. Met amplification drives acquired resistance to AZD4547 in H1581AR cells by activating ErbB3. Combination treatment with FGFR inhibitors and an anaplastic lymphoma kinase (ALK)/Met inhibitor, crizotinib, or Met-specific short interfering RNA (siRNA) synergistically inhibited cell proliferation in both H1581AR and H1581BR cells. Conversely, ectopic expression of Met in H1581 cells conferred resistance to AZD4547 and BAY1163877. Acquired resistance to FGFR inhibitors not only altered cellular morphology, but also promoted migration and invasion of resistant clones, in part by inducing epithelial-to-mesenchymal transition. Taken together, our data suggest that Met activation is sufficient to bypass dependency on FGFR signaling. Concurrent inhibition of the Met and FGFR pathways may have synergistic clinical benefits when targeting FGFR-dependent LC.