Abstract 5969: VRK1 can be a therapeutic target in small cell neuroendocrine carcinoma of the uterine cervix

Abstract Objective: Small cell neuroendocrine carcinoma of the uterine cervix (SCNEC) is extremely rare but highly aggressive and its prognosis is usually poor. Vaccinia-related kinase (VRK)1 is a serine/threonine protein kinase that is involved in cell proliferation by regulating cell-cycle progression and inducing cell-cycle arrest in response to stress signals. VRK2 belongs to the same family as VRK1, and they are paralogs. VRK1 has been reported as a potential therapeutic target in nervous system tumors with low VRK2 expression. Previously, we identified high expression of VRK1 in SCNEC through proteomic analysis of isolated organoids. The objective of the present study is to investigate the effect of VRK1 on the proliferation of SCNEC and its potential as a therapeutic target. Methods: The mRNA and protein expression of VRK1 and VRK2 in ten organoids and two cell lines derived from SCNEC were examined and compared with cervical cancer of other histological subtypes by RNA microarray and western blot analysis. The effect of VRK1 on tumor growth in vitro and in vivo (xenograft model) were evaluated by shRNA-mediated knockdown of VRK1 (shVRK1). RNA-seq was performed from the xenograft tumors. The effects of shVRK1 on cell proliferation were evaluated under various levels of oxidative stress induced by H2O2. Results: VRK1 expression was higher in organoids and cell lines derived from SCNEC than those derived from squamous cell carcinoma and adenocarcinoma, while VRK2 expression was lower in SCNEC. Tumor growth was suppressed significantly by shVRK1 in vivo (mean weight: cell line 1: 0.62 vs 0.06g, p<0.05, 2: 1.79 vs 0.58g, p<0.01). Gene ontology analysis of RNA-seq data suggested that VRK1 is related to cellular responses to stress. Proliferation was slightly suppressed by shVRK1 under normal conditions; however, it was significantly enhanced under oxidative stress (Cell line 1: in shVRK1, -14.0% without oxidative stress vs -54.9% under H2O2 750μM, p<0.01, Cell line 2: similar to Cell line 1). Conclusion: SCNEC exhibited high VRK1 and low VRK2 expression, and the tumor suppressive effect of shVRK1 was more significant in vivo than in vitro. VRK1 may play a role in the tumor microenvironment, including oxidative stress, and is a potential therapeutic target for SCNEC. Citation Format: Mariya Kobayashi, Satoshi Nakagawa, Mizuki Kanda, Yuji Kamei, Masuda Tatsuo, Mamoru Kakuda, Kosuke Hiramatsu, Toshihiro Kimura, Yutaka Ueda, Takayuki Enomoto, Masahiro Inoue, Tadashi Kimura. VRK1 can be a therapeutic target in small cell neuroendocrine carcinoma of the uterine cervix [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5969.