Scirrhous gastric cancer, which has the worst prognosis among the various types of gastric cancer, is highly invasive and associated with abundant stromal fibroblasts. Although cancer-associated fibroblasts (CAFs) have been proposed to generate a tumor-supportive extracellular matrix that promotes the expansion of this type of cancer, the molecular mechanisms by which CAFs assist cancer cells are not yet fully understood. Here, we show for the first time that Asporin, a small leucine-rich proteoglycan (SLRP), is predominantly expressed in CAFs, and has essential roles in promoting co-invasion of CAFs and cancer cells. CAFs of scirrhous gastric cancer possess high potential for invasion, and invasion by CAFs frequently proceeded invasion by cancer cells, both in vitro and in vivo. Expression of Asporin was induced in fibroblasts by exposure to gastric cancer cells. Asporin secreted from CAFs activates Rac1 via an interaction with CD44 and promotes invasion by CAFs themselves. Moreover, Asporin promoted invasion by neighboring cancer cells, via paracrine effects mediated by activation of the CD44-Rac1 pathway. These results suggest that Asporin is a unique SLRP that promotes progression of scirrhous gastric cancer and is required for coordinated invasion by CAFs and cancer cells. Therefore, Asporin may represent a new therapeutic target molecule for the development of drugs aimed at manipulating the cancer microenvironment.

Scirrhous gastric cancer is frequently associated with peritoneal dissemination, and the interaction of cancer cells with peritoneal mesothelial cells (PMCs) is crucial for the establishment of the metastasis in the peritoneum. Although cells derived from PMCs are detected within tumors of peritoneal carcinomatosis, how PMCs are incorporated into tumor architecture is not understood. The present study shows that PMCs create the invasion front of peritoneal carcinomatosis, which depends on activation of Tks5 in PMCs. In peritoneal tumor implants, PMCs represent majority of cells located at the invasive edge of the cancer tissue. Exogenously implanted PMCs and host PMCs aggressively invade into abdominal wall upon the peritoneal inoculation of cancer cells, and PMCs locate ahead of cancer cells in the direction of invasion. Tks5, a substrate of Src kinase, is predominantly expressed in the PMCs of cancer tissue, and promotes the invasion of PMCs and cancer cells. Expression and activation of Tks5 was induced in PMCs following their exposure to gastric cancer cells, and increased Tks5 expression was detected in PMCs located at the invasion front. Reduced Tks5 expression in PMCs blocked PMC invasion, which in turn prevents cancer cell invasion both in vitro and in vivo. The peritoneal dissemination of gastric cancer was significantly increased by mixing cancer cells and PMCs, and was suppressed by knockdown of Tks5 in PMCs. These results suggest that cancer-activated PMCs create invasion front by guiding cancer cells. Signaling leading to Tks5 activation in PMCs may be a suitable therapeutic target for prevention of peritoneal carcinomatosis.

Agr2 is a disulfide isomerase residing in the endoplasmic reticulum (ER), which physiologically regulates protein folding and mediates resistance to ER stress. Agr2 is overexpressed in adenocarcinomas of various organs, where it participates in neoplastic transformation and metastasis, therefore acts as a pro-oncogenic protein. Besides its normal localization in the ER, Agr2 is also found in the serum and urine of cancer patients, although the physiological significance of extracellular Agr2 is poorly understood. In this study, we demonstrated that extracellular Agr2 can activate stromal fibroblasts and promote fibroblastassociated cancer invasion in gastric signet-ring cell carcinoma (SRCC), where Agr2 is highly expressed. Agr2 secreted from SRCC cells was incorporated by the surrounding gastric fibroblasts and promoted invasion by these cells. In turn, activated fibroblasts coordinated the invasive behavior of fibroblasts and cancer cells. Our findings suggested that Agr2 drives progression of gastric SRCC by exerting paracrine effects on fibroblasts in the tumor microenvironment, acting also to increase the growth and resistance of SRCC cells to oxidative and hypoxic stress as cell autonomous effects. Cancer Res; 75(2); 356-66. Ó2014 AACR.

Abstract. Mutations at codons 12 and 13 of the KRAS gene have been identified as level I predictive biomarkers against the treatment of advanced colorectal cancer with anti-epidermal growth factor receptor (EGFR) monoclonal antibodies. It is thought that the genetic analysis of KRAS mutations associated with metastatic colorectal cancer can be routinely conducted using DNA obtained on one occasion from one organ, from the primary or a metastatic site, whichever is preferentially available. However, the issue of tumor heterogeneity resulting from acquired/intratumoral mutations remains. Recently, the possibility of acquired/intratumoral mutations in the KRAS gene has been reported by two research groups and has ranged from 7.4 to 15.4%. Specimens were collected from advanced colorectal cancer patients with resected primary, and at least one metastatic, site. Direct sequence analysis was performed for KRAS, BRAF and PIK3CA, and immunohistochemistry for glutathione S-transferase II (GSTP) and EGFR. In the current study, we identified an acquired mutation rate of approximately 11.1% in the KRAS gene (1/9). This figure is not negligible. Our observation indicates, particularly in the case of metastatic recurrence after a long interval, that there may be considerable tumor heterogeneity resulting from acquired or intratumoral mutations of the KRAS gene.

Coronavirus disease 2019 (COVID-19) was thought to have respiratory symptoms as the main manifestation, but it has become clear that extrapulmonary symptoms such as gastrointestinal disorders also occur. There are several reports of intussusception associated with COVID-19 in children, but these are rare in adults. In this report, we present a case of cystic intestinal duplication that enlarged during the course of COVID-19 treatment and resulted in intussusception. Right hemicolectomy was performed for intussusception due to the cystic lesion. To the best of our knowledge, this is the first resected case of intussusception due to alimentary tract duplication after COVID-19 infection.