Abstract 529: The significance of activated PI3K/AKT pathway in FGFR3-TACC3 fusion positive cervical cancer
Authors: Tamura Ryo , Yoshihara Kosuke , Saito Tetsuya , Ishimura Ryosuke , Martínez-Ledesma Emmanuel , Mori Yutaro , Yamawaki Kaoru , Suda Kazuaki , Ishiguro Tatsuya , Aoki Yoichi , Sato Seiya , Itamochi Hiroaki , Komatsu Masaaki , Verhaak Roeland , Enomoto Takayuki 
Published: July 2017

Abstract
Uterine cervical cancer is one of the most common cancer in women worldwide, and the prognosis in advanced or recurrent cases remains poor because of no effective molecular target therapies for this disease. The aim of our study is to identify and validate therapeutically targetable gene fusions in uterine cervical cancer, leading to the development of new therapeutic strategies. We have analyzed RNA sequencing data of 253 TCGA cervical cancer samples to search for gene fusions by using PRADA algorithm, and validated recurrent fusions in our Japanese dataset (n = 100) by RT-PCR and sanger sequencing. In TCGA samples, we detected 358 fusion transcripts and extracted 3 kinds of recurrent in-frame fusion transcripts (FGFR3-TACC3, ARL8B-ITPR1 and NXN-ABR). We focused on FGFR3-TACC3 fusion as a candidate of therapeutic kinase fusion and identified FGFR3-TACC3 fusion in 2 of 253 (0.8%) TCGA samples and 2 of 100 (2%) Japanese samples. All of fusion positive samples, which were histologically diagnosed as squamous cell carcinoma, showed high expression of both FGFR3 and TACC3 genes. To evaluate the possibility as therapeutically targetable fusions in uterine cervical cancer, we transfected FGFR3-TACC3, wild type FGFR3 and TACC3 transcripts to normal immortalized cervical keratinocytes derived from ectocervix (Ect1/E6E7) and four uterine cervical cancer cell lines (SiHa, ME180, HeLa, CaSki). Continuous expression of FGFR3-TACC3 fusion transcript led to anchorage-independent growth in Ect1/E6E7 and the dramatically alteration of cell proliferation in all cancer cell lines. On the other hand, no obvious phenotype change was observed in FGFR3 or TACC3 transfected cells. Western blotting analysis demonstrated that MAPK pathway was activated in all the fusion transfected cell lines but PI3K/AKT pathway was activated only in ME180 and CaSki harboring PIK3CA mutation. Fusion transfected cell lines exhibited high sensitivity to fusion specific siRNA and FGFR inhibitor compared to control. Although PI3K/AKT activated cell lines (ME180 and CaSki) showed less effective against FGFR inhibitor compared to PI3K/AKT neutral cell lines (SiHa and HeLa), combined inhibition of FGFR and AKT had a synergic effect in PI3K/AKT activated cell lines. Our findings suggest FGFR3-TACC3 fusion gene is an oncogenic driver event and therapeutic target in a fraction of cervical cancer. When FGFR3-TACC3 fusion positive cervical cancer is treated by FGFR inhibitor, genomic background such as PI3K/AKT status should be considered.
Citation Format: Ryo Tamura, Kosuke Yoshihara, Tetsuya Saito, Ryosuke Ishimura, Emmanuel Martínez-Ledesma, Yutaro Mori, Kaoru Yamawaki, Kazuaki Suda, Tatsuya Ishiguro, Yoichi Aoki, Seiya Sato, Hiroaki Itamochi, Masaaki Komatsu, Roeland Verhaak, Takayuki Enomoto. The significance of activated PI3K/AKT pathway in FGFR3-TACC3 fusion positive cervical cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 529. doi:10.1158/1538-7445.AM2017-529