Abstract 372: VGF is functionally responsible for chemotherapy resistance in non-small cell lung cancer
Authors: Nogami Wataru , Tona Yumi , Tofukuji Soichi , Ishioka Yoshino , Matsumoto Mitsunobu , Yamada Hajime , Kuwabara Kenji , Tanaka Hidekazu , Adachi Shigeki , Yamamoto Yoko , Kanzaki Ryu , Funaki Soichiro , Shintani Yasushi , Okumura Meinoshin , Nomura Taisei 
Published: August 2019

Abstract
Despite the success of immune checkpoint therapy, most non-small cell lung cancer (NSCLC) patients still receive conventional chemotherapy. Overcoming chemotherapy resistance by identifying specific targets should improve cancer treatment and patient survival. In this study, we examined a prospective chemotherapy-resistant subpopulation in NCI-H1975 NSCLC cells and identified a novel target, neurosecretory protein VGF (VGF). Using flow cytometry, we first analyzed the expression profile of cancer stem cell markers in 100 cancer cell lines and found that NCI-H1975 cells could be divided into three subpopulations, CD44-low (CD44-L), CD44-middle (CD44-M) and CD44-high cells based on the expression pattern of CD44. CD44-M cells account for less than 5% of the NCI-H1975 cells under normal conditions, but only this subpopulation can proliferate in vitro and in vivo after treatment with cytotoxic agents, such as paclitaxel, pemetrexed and 5-fluorouracil. Affymetrix microarray analysis revealed that VGF is specifically expressed in CD44-M cells and we hypothesized that VGF would play a critical role in chemotherapy resistance. We next employed patient-derived xenograft (PDX) models of NSCLC to confirm this hypothesis with human clinical samples. NOD/SCID mice were subcutaneously transplanted with PDX and treated with either vehicle or paclitaxel (12 mg/kg, Q3Dx3, i.v.). VGF immunohistochemistry on resected PDX revealed that the number of VGF-expressing cells increased 5.6-fold in the paclitaxel-treated group compared to the vehicle control. We also performed VGF immunohistochemistry on NSCLC surgical specimens which were obtained from 127 patients, consisting of 42 neoadjuvant chemotherapy treated cases and 85 non-treated cases. The frequency of VGF-expressing specimens was higher in neoadjuvant chemotherapy treated cases (50%) than non-treated cases (18%). These results suggest that VGF-expressing tumor subpopulation is paclitaxel-resistant even in clinical settings. We also analyzed the molecular functions of VGF. Knockdown of VGF expression by siRNAs could signifıcantly suppress paclitaxel resistance in CD44-M cells. On the other hand, overexpression of VGF could significantly induce paclitaxel resistance in CD44-L cells. These results suggest that VGF is functionally responsible for chemotherapy resistance in NSCLC patients and combined administration of an anti-VGF drug and chemotherapy could be effective for preventing cancer recurrence and prolonging cancer free survival.
Citation Format: Wataru Nogami, Yumi Tona, Soichi Tofukuji, Yoshino Ishioka, Mitsunobu Matsumoto, Hajime Yamada, Kenji Kuwabara, Hidekazu Tanaka, Shigeki Adachi, Yoko Yamamoto, Ryu Kanzaki, Soichiro Funaki, Yasushi Shintani, Meinoshin Okumura, Taisei Nomura. VGF is functionally responsible for chemotherapy resistance in non-small cell lung cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 372.