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Aim: Mutation spectrum of TP53 in gastric cancer (GC) has been investigated world-widely, but a comparison of mutation spectrum among GCs from various regions in the world are still sparsely documented. In order to identify the difference of TP53 mutation spectrum in GCs in Eastern Europe and in East Asia, we sequenced TP53 in GCs from Eastern Europe, Lujiang (China), and Yokohama, Kanagawa (Japan) and identified the feature of TP53 mutations of GC in these regions. Subjects and Method: In total, 689 tissue samples of GC were analyzed: 288 samples from East European populations (25 from Hungary, 71 from Poland and 192 from Romania), 268 from Yokohama, Kanagawa, Japan and 133 from Lujiang, Anhui province, China. DNA was extracted from FFPE tissue of Chinese, East European cases; and from frozen tissue of Japanese GCs. PCR products were direct-sequenced by Sanger method, and in ambiguous cases, PCR product was cloned and up to 8 clones were sequenced. We used No. NC_000017.11(hg38) as the reference sequence of TP53. Mutation patterns were categorized into nine groups: six base substitutions, insertion, deletion and deletion-insertion. Within G:C>A:T mutations the mutations in CpG and non-CpG sites were divided. Furthermore, 40 cases of Rwanda GC were compared in the world for mutation spectrum. The Cancer Genome Atlas data (TCGA, ver.R20, July, 2019) having somatic mutation list of GCs from Whites, Asians, and other ethnicities were used as a reference for our data. Results: The most frequent base substitutions were G:C>A:T transition in all the areas investigated. The G:C>A:T transition in non-CpG sites were prominent in East European GCs, compared with Asian ones. Mutation pattern from TCGA data revealed the same trend between GCs from White (TCGA category) vs Asian countries. Chinese and Japanese GCs showed higher ratio of G:C>A:T transition in CpG sites and A:T>G:C mutation was more prevalent in Asian countries. Conclusion: The divergence in mutation spectrum of GC in different areas in the world may reflect various pathogeneses and etiologies of GC, region to region. Diversified mutation spectrum in GC in Eastern Europe may suggest GC in Europe has different carcinogenic pathway of those from Asia. Whether the Rwanda pattern belong to Asian or East European would be interesting. Citation Format: Hiroko Natsume, Kinga Szczepaniak, Hidetaka Yamada, Yuji Iwashita, Marta Gędek, Jelena Šuto, Rika Kasajima, Felix Manirakiza, Augustin Nzitakera, Rei Ishikawa, Eric Rutaganda, François Ngabonziza, Benoit Seminega, Placide Kamali, Vincent Dusabejambo, Belson Rugwizangoga, Nobuhito Nobuhito, Yaping Wang, Yohei Miyagi, Simona Gurzu, Haruhiko Sugimura. Non-CpG sites preference in G:C>A:T transition of TP53 in gastric cancer of Eastern Europe (Poland, Romania and Hungary) compared to East Asian countries (China and Japan) : gastric cancer in the world, mutation spectrum revisited [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2609.