Characterization of Poorly Cohesive and Signet Ring Cell Carcinomas and Identification of PTPRM as a Diagnostic Marker

SIMPLE SUMMARY: The classification of signet ring cell (SRC) carcinoma has been inconsistent and SRC carcinoma was classified as a subtype gastric cancer of poorly cohesive (PC) carcinoma. SRC and PC gastric carcinomas are morphologically similar but has been suggested to exhibit different biological behavior. We compared clinical and molecular characteristics of SRC and PC carcinomas. SRC and PC carcinomas showed significantly different clinical behavior that SRC carcinoma was associated with favorable clinical factors, suggesting that these subtypes should be classified and treated differently. SRC and PC carcinomas shared common transcriptome expression patterns, however, PC carcinomas showed an increased expression of genes related to cancer progression. Among genes differentially expressed between PC and SRC carcinomas, protein tyrosine phosphatase receptor type M (PTPRM) was overexpressed in PC and related to unfavorable clinical factors. PTPRM was identified as a potential diagnostic and prognostic biomarker for PC carcinoma. ABSTRACT: Background and aims. Signet ring cell (SRC) and poorly cohesive (PC) gastric carcinomas are morphologically similar but exhibit different biological behavior. We compared the clinical and molecular characteristics of SRC and PC carcinomas. Methods. Diffuse-type gastric cancer (GC) cases were classified into SRC carcinomas (>90% of SRCs), PC carcinomas (<10% of SRCs), and combined PC/SRC carcinomas (≤90% but ≥10% of SRCs). The gene expression patterns in SRC and PC carcinomas were examined by transcriptome and protein immunohistochemistry analyses, and diagnostic and prognostic biomarkers were identified. Results. SRC and PC carcinomas showed significantly different clinical behaviors but shared common RNA expression patterns. PC carcinomas showed an increased expression of genes related to cancer progression. Among genes differentially expressed between PC and SRC carcinomas, protein tyrosine phosphatase receptor type M (PTPRM) was overexpressed in PC and related to unfavorable clinical factors. Conclusion. We found that PC and SRC carcinomas had distinct clinical characteristics and should be classified as different carcinoma types. PTPRM was identified as a potential diagnostic and prognostic biomarker for PC carcinomas and could represent a potential therapeutic target.