Abstract 3582: Epidermal growth factor receptor and anaplastic lymphoma kinase bypass signaling in oral squamous cell carcinomain vivo

Oral squamous cell carcinoma (OSCC) is an insidious disease with poor prognosis. This is due to invasive disease that is refractive to conventional therapies. We reported a gene-set of hypomethylated loci in metastatic OSCC involved in Epidermal Growth Factor Receptor (EGFR) signaling. EGFR over-expression is an early event in OSCC however therapies targeting EGFR have had dismal results. Our studies showed hypomethylation of Anaplastic Lymphoma Kinase (ALK) correlates with metastatic OSCC. ALK and EGFR signaling drive glioblastoma and non-small cell lung cancers (NSCLC). Furthermore, NSCLC that develop resistance to ALK inhibition demonstrate activation of EGFR bypass signaling. Based upon these findings, we hypothesize that simultaneous targeting of both ALK and EGFR in OSCC will yield greater anti-tumor activity than single drug therapies. Our objective was to assess expression and activation of EGFR and ALK signaling pathways in response to therapies targeting EGFR and/or ALK in vitro and in mouse OSCC xenograft models. Expression of total and activated EGFR and ALK was analyzed in HSC3 cells (invasive) and SCC4 cells (non-invasive) using western blot analysis. Effects on downstream signaling molecules (AKT, STAT3, and RAS) were also evaluated following treatments with TAE684 (ALK inhibitor) and/or Gefitinib (EGFR inhibitor). Anti-tumor effects of TAE684 and/or Gefitinib were evaluated in mouse OSCC xenograft models using HSC3 and SCC4 cell lines. This study revealed that HSC3 and SCC4 cell lines have unique growth, invasion, and signaling profiles resulting in varying responses to treatments targeting ALK and/or EGFR. HSC3 cells express ALK and have active EGFR whereas SCC4 cells have low ALK expression and low EGFR activity. Subsequently, HSC3 xenografts were sensitive to Gefitinib and co-targeting ALK resulted in an additive effect. Targeting ALK alone had no effect on tumor growth. Similar to NSCLC, western blot analysis revealed that ALK inhibition alone induces increased activation of EGFR bypass signaling in both HSC3 and SCC4 cells. In contrast SCC4 xenografts failed to respond to TAE684 and/or Gefitinib treatments. Co-treatment with TAE684 and Gefitinib down regulated the already low EGFR activity. Downstream effector molecules AKT and STAT3 had reduced activity in response to co-treatments in both HSC3 and SCC4 cell lines. Conversely, MAPK activity increased with all treatments in both cell lines. Therefore, we conclude that OSCC with active EGFR and ALK signaling are responsive to combination treatments targeting ALK and EGFR resulting in more efficacious anti-tumor effects than single drug therapies. Furthermore, single anti-ALK therapy induces compensatory EGFR activation and has no effect on tumor growth. Additional parallel pathways may account for elevated MAPK activity in response to all treatments and warrants further investigation. Citation Format: Cara B. Gonzales, Heping Chen, Jorge J. De La Chapa, Nameer B. Kirma. Epidermal growth factor receptor and anaplastic lymphoma kinase bypass signaling in oral squamous cell carcinoma in vivo . [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3582. doi:10.1158/1538-7445.AM2015-3582