Abstract 2517: The amplification of TPX2 is a potential biomarker of oxaliplatin-sensitivity of colorectal cancers (CRCs) with CIN phenotype

Abstract The amplification of Chr20q11. 21 harboring TPX2 gene is the most frequent copy number alteration among the cases of colorectal cancers (CRCs), especially left-sided ones. We retrospectively examined 2828 cases of CRC patients who took cancer-genome panel tests in Japan between June 2019 and November 2022. The time to first-line treatment failure was longer with regimen with oxaliplatin than with those with irinotecan in CRC patients with Chr20q11, 21 amplification (12. 2 versus 9. 2 months, p=0. 0481). Oxaliplatin induces double-strand breaks (DSBs) and then cellular apoptosis. A key event of the DNA damage response to DSBs for cellular survival is the extensive phosphorylation of Ser139 of Histone H2AX adjacent to the chromosomal break. TPX2 whose gene resides in Chr20q11, 21 has been reported to repress the phosphorylation of H2AX upon ionizing radiation. The purpose of this study is to identify the relationship between the amplification of TPX2 and oxaliplatin sensitivity in human CRCs. The knockdown of TPX2 decreased the oxaliplatin-susceptibility of COLO320 and Caco-2, CIN phenotype CRC cell lines which highly expressed TPX2. However, TPX2 knockdown did not reduce the oxaliplatin sensitivity of HCT-116, an MSI phenotype CRC cell line with low-level of TPX2 expression. The knockdown of TPX2 in CIN phenotype CRC cells, not in the MSI phenotype CRC cells, enhanced the phosphorylation of H2AX upon the DNA-damage induced by oxaliplatin. These findings suggest that amplification of TPX2 contributes to the oxaliplatin-susceptibility of CRCs with CIN phenotype through DNA repair machinery. Citation Format: Shohei Ueno, Taichi Isobe, Ryosuke Taguchi, Kenji Tsuchihashi, Koichi Akashi, Eishi Baba. The amplification of TPX2 is a potential biomarker of oxaliplatin-sensitivity of colorectal cancers (CRCs) with CIN phenotype 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 (6Suppl): Abstract nr 2517.