Mechanisms of resistance for HNSCC to cisplatin (CDDP), the foundational chemotherapeutic agent in the treatment of this disease, remain poorly understood. We previously demonstrated that cisplatin resistance (CR) can be overcome by targeting Trk receptor. In the current study, we explored the potential mechanistic role of the BDNF-TrkB signaling system in the development of CDDP resistance in HNSCC. Utilizing an in vitro system of acquired CR, we confirmed a substantial up-regulation of both BDNF and TrkB at the protein and mRNA levels in CR cells, suggesting an autocrine pathway dysregulation in this system. Exogenous BDNF stimulation led to an enhanced expression of the drug-resistance and anti-apoptotic proteins MDR1 and XiAP, respectively, in a dose-dependently manner, demonstrating a key role for BDNF-TrkB signaling in modulating the response to cytotoxic agents. In addition, modulation of TrkB expression induced an enhanced sensitivity of cells to CDDP in HNSCC. Moreover, genetic suppression of TrkB resulted in changes in expression of Bim, XiAP, and MDR1 contributing to HNSCC survival. To elucidate intracellular signaling pathways responsible for mechanisms underlying BDNF/TrkB induced CDDP-resistance, we analyzed expression levels of these molecules following inhibition of Akt. Inhibition of Akt eliminated BDNF effect on MDR1 and Bim expression in OSC-19P cells as well as modulated expressions of MDR1, Bim, and XiAP in OSC-19CR cells. These results suggest BDNF/TrkB system plays critical roles in CDDP-resistance development by utilizing Akt-dependent signaling pathways.

Targeting HER2 may be a promising avenue for the development of novel therapies for SNUC. © 2016 Wiley Periodicals, Inc. Head Neck 38: E1926-E1934, 2016.

It has long been known that the tumor microenvironment contributes to the proliferation and survival of neoplasms through the constant interaction with the stromal and immune compartments. In this investigation, we explored the role of cancer-associated fibroblasts (CAFs) in the regulation of the tumor microenvironment in head and neck squamous cell carcinoma (HNSCC) though a complex intercellular BDNF-TrkB signaling system. Our studies show that conditioned media derived from patient-derived CAFs promoted HNSCC cell proliferation, in vitro cell migration, cell invasion and chemotherapy resistance, compared to normal fibroblasts. Furthermore, examination of the in vivo impact of CAF pathophysiology in the tumor microenvironment in animal xenograft models revealed that HNSCC cell lines in combination with CAFs promoted tumor growth and increased incidence of lymphovascular metastasis as compared to injection of tumor cells or CAF cells alone. Using pharmacological and genetic alterations, we mechanistically demonstrate the critical importance of BDNF-TrkB signaling in the tumor microenvironment. These investigations further support the rationale for BDNF/TRKB targeted therapy against in the treatment of HNSCC.

Head and neck squamous cell carcinoma (HNSCC) is a biologically aggressive disease, with an annual incidence of approximately 44,000 cases in the United States, and over 650,000 worldwide. While strides have been made in surgical techniques, refinement of radiation delivery and intensification of local-regional treatment with chemotherapeutic strategies, a significant number of patients succumb to distant metastasis and local-regional failure. Thus, there is a compelling need for new treatment regimens that target relevant molecular pathways. The TRK family of receptor tyrosine kinases (RTK) plays important roles in embryonic development and mediates diverse processes including cellular proliferation, migration, stem cell survival and physiologic angiogenesis. Several lines of evidence support the role of TrkB for invasion and metastasis in various solid tumor models. Our laboratory has established the critical role of the TrkB receptor in human HNSCC tumors and as a mediator of EMT in this disease. TrkB activates diverse downstream signaling cascades that ultimately induce cellular proliferation, invasion and survival mechanisms, through AKT, STAT3 and MAPK pathways. Emerging evidence also supports a role for TrkB in the tumor microenvironment and as a mediator of chemotherapy resistance in HNSCC. Thus, TrkB is a potentially important target for novel treatment approaches for HNSCC. Therapeutic modulation of TrkB function has been supported in the literature by the development of small molecule inhibitors (SMIs) that have putative activity against TrkB but have not resulted in clinical effectiveness. Utilizing computational-based structural modeling, compounds were designed to inhibit the ATP-binding pocket of the TrkB RTK. Synthetic templates were proposed for building a library of potential inhibitors. An induced fit docking protocol was utilized to generate a model capable of evaluating the putative compounds. After an initial model was constructed, the top 20% of scoring structures from docking were evaluated in ten other kinases and the data was fed into a Knime workflow along with ADME calculated properties. The filtering led to 19 structures and the distribution of scores suggests that the selected compound should demonstrate a modest selectivity for TrkB over other kinases and seven of those structures were made and were examined in-vitro. The MTT method was utilized for proliferation analysis in HNSCC cell lines. Proliferation analysis revealed significant growth inhibition for compounds Trk-4 (IC50=3.5) and Trk-5 (IC50=10.4) in all tested HNSCC cell lines. Conclusions: Computational based approaches for the development of TrkB RTK inhibitors are feasible. In vitro validation confirmed the cytotoxic nature of these novel compounds in cell lines with high expression of TrkB. Further validation of efficacy in an animal model and RTK selectivity are warranted. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr A122.