PIK3CA mutations are associated with increased tumor aggressiveness and Akt activation in gastric cancer
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Ji-Won Kim1,*, Hye Seung Lee2,*, Kyung Han Nam3, Soyeon Ahn4, Jin Won Kim1, Sang-Hoon Ahn5, Do Joong Park5, Hyung-Ho Kim5 and Keun-Wook Lee1
1Department of Internal Medicine, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam 13620, Korea
2Department of Pathology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam 13620, Korea
3Department of Pathology, Haeundae Paik Hospital, Inje University College of Medicine, Busan 48108, Korea
4Medical Research Collaborating Center, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam 13620, Korea
5Department of Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam 13620, Korea
*These authors contributed equally to this work
Keun-Wook Lee, email: firstname.lastname@example.org
Keywords: PIK3CA, mutation, AKT, expression, gastric cancer
Received: October 11, 2016 Accepted: June 10, 2017 Published: June 28, 2017
PIK3CA mutations are frequent in gastric cancer. However, their pathological and clinical implications are still unclear. We analyzed the clinicopathological characteristics according to the PIK3CA mutation status of patients with stage IB–IV disease who underwent gastrectomy between May 2003 and Dec. 2005 (cohort 1; n = 302) and of those with stage IV disease who received gastrectomy between Jul. 2006 and Dec. 2012 (cohort 2; n = 120). PIK3CA mutations were detected in 40 patients (13.2%) in cohort 1. In these patients, PIK3CA-mutant tumors were more frequently located in the upper third of the stomach (p = 0.021) and significantly showed poorly differentiated histology (p = 0.018) and increased lymphatic (p = 0.015), vascular (p = 0.005), and perineural invasion (p = 0.026). In addition, these tumors showed significantly increased lymphocyte and neutrophil infiltration in cancer stroma (p < 0.001), Epstein–Barr virus positivity (p < 0.001), and microsatellite instability (p = 0.015). Cytoplasmic Akt expression was significantly increased in these tumors (p = 0.001). In cohort 2, PIK3CA mutations were identified in 15 patients (12.5%). PIK3CA-mutant tumors showed significantly increased vascular invasion (p = 0.019) and microsatellite instability (p = 0.041). In addition, cytoplasmic Akt expression was also significantly increased (p = 0.018). However, in both cohorts, PIK3CA mutations were not associated with the prognosis of patients. In conclusion, PIK3CA mutations were associated with increased tumor aggressiveness, especially in locoregional disease, and Akt activation in gastric cancer. Our data suggest that PIK3CA-mutated gastric cancer is a distinct disease entity, which might need a different therapeutic approach.
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