Aberrant expression of connexin 26 is associated with lung metastasis of colorectal cancer.

PURPOSE: Connexin 26 (Cx26) is one of the gap junction-forming family members classically considered to be tumor suppressors. However, recent studies show association of elevated expression of Cx26 with poor prognosis in several human malignancies. Furthermore, Cx26 has been observed to be indispensable to spontaneous metastasis of melanoma cells. Here, we assessed Cx26 expression in primary colorectal cancer (CRC) and the metastatic lesions to elucidate its role in metastasis. EXPERIMENTAL DESIGN: Cx26 expression was assessed in 25 adenomas, 167 CRCs, and normal mucosa, together with the metastatic lesions. RESULTS: Normal mucosa and adenomatous tissue expressed Cx26 mainly in the plasma membrane, whereas cancer cells mostly contained Cx26 in the cytoplasm. The incidence of aberrant Cx26 expression varied widely in CRC (mean, 49.5 +/- 35.5%), and the expression levels were confirmed by Western blot and quantitative reverse transcription-PCR. Clinicopathologic survey revealed association of high expression with less differentiated histology and venous invasion (P = 0.0053 and P = 0.0084, respectively). Notably, high Cx26 expression was associated with shorter disease-free survival and shorter lung metastasis-free survival in 154 curatively resected CRC sets (P = 0.041 and P = 0.028, respectively). Survey of metastatic lesions revealed that lung metastasis, but not liver and lymph nodes metastases, expressed higher Cx26 than the CRC series or corresponding primary CRCs (P < 0.0001 and P = 0.0001, respectively). CONCLUSIONS: These findings suggest that aberrant expression of Cx26 plays an essential role in lung metastasis. Thus, Cx26 is a promising therapeutic target, particularly for CRC patients who develop lung metastasis.

Overexpression of connexin 26 in carcinoma of the pancreas.

Contrary to the previously purported role of gap junction (GJ) associated-protein connexin 26 (Cx26) as a tumor suppressor, increased expression of Cx26 has recently been demonstrated in several human malignancies. Surprisingly, this high expression is reportedly related to poor prognosis in squamous cell lung carcinoma and breast cancer. In this study, we examined levels of Cx26 in various human gastrointestinal (GI) carcinomas, with a focus on pancreatic carcinomas, using immunohistochemistry. Many GI carcinomas displayed abundant Cx26 expression, predominantly in the cytoplasm. Cx26 was detected in 5/8 gastric cancers (62.5%), 6/8 squamous cell carcinomas of the esophagus (75.0%), 7/8 pancreatic cancers (87.5%) and 7/8 colon cancer cases (87.5%). However, Cx26 expression was not present in hepatocellular carcinoma (HCC, 0/8). Extensive immunohistochemical examination was performed on pancreatic carcinomas, revealing strong expression of Cx26 protein in 30/43 cases (70%), weak expression in 6/43 (14%) and no expression in 7/43 (16%). The present study demonstrated up-regulated Cx26 expression in a considerable percentage of GI carcinomas, with the exception of HCC. Our findings suggest that Cx26 may be involved in some of the malignant processes of GI cancers, and especially in pancreatic carcinomas.

Hypoxia-induced up-regulation of angiopoietin-2 in colorectal cancer.

Angiogenesis is a compensatory mechanism that enables malignant tumors to survive in an oxygen-deficient environment. To test our hypothesis that hypoxia stimulates the production of angiopoietin-2 (Ang-2) in colorectal cancer (CRC), we investigated the expression of Ang-2 in three cultured CRC cell lines, and in specimens from 11 CRC metastatic liver tumors. Hypoxia-induced Ang-2 mRNA expression was clearly evident in HCT116 cells that did not express Ang-2 under normoxic conditions. Ang-2 mRNA was detected only after 48 h in hypoxic serum-deprived cultures in a LoVo cell line, and under both normoxic and hypoxic conditions without any noticeable difference in the HT29 cells. There was a stepwise increase in Ang-2 expression from the periphery to the central part of the liver metastatic foci, whereas an inverse result was noted in tumor blood vessels, with a gradual decrease in CD31-positive ECs from the edge to the central region of the metastatic lesion. An expression pattern similar to Ang-2 was found in glucose transporter 1 (Glut-1), a known hypoxia-induced factor. These findings suggest that hypoxia plays an important role in inducing the expression of Ang-2 in CRC.

[Complete response of primary tumor in a case of advanced gastric cancer with liver metastasis treated by TS-1 plus divided administration of CDDP].

A 62-year-old female patient was hospitalized for general fatigue and appetite loss. Type 3 gastric cancer (moderate differentiated adenocarcinoma) with liver metastasis (S8) and direct invasion to the retro-peritoneal space and duodenal third portion was detected by endoscopic and radiographic examination. This case was judged to be unresectable from these findings. TS-1 plus divided administration of CDDP was performed. TS-1 (100 mg/day) was administrated from day 1 to 21 followed by 14 days rest as one course. CDDP (20 mg/m2) was infused for 2 hours on day 1, 8, and 15. One course was done in the hospital, and the following 2 courses as ambulatory treatment. Grade 2 neutropenia was observed as an adverse reaction. At the completion of 3 courses, partial response in the primary tumor, complete response in the duodenal third portion and no change in the liver metastasis were assessed by examination. Because of this remarkable down-staging, distal gastrectomy and radiofrequency ablation (RFA) for liver metastasis were performed. There was no evidence of direct invasion to the other organs from the primary tumor in intraoperative findings. Pathological examination revealed the disappearance of carcinoma cell in the resected stomach and the surrounding lymphnodes. In conclusion, this chemotherapy regimen has an excellent antitumor effect with low toxicities. Therefore, this regimen was comparatively safe for outpatients and was an effective neo-adjuvant chemotherapy.