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A significant difference was observed in the Dukes stage (p = 0.0438). Netrin-1 receptors might act as a tumor suppressor in colorectal cancers, and thus methylation might present a malignant potential in colorectal cancer.

The Mus81 gene encodes a critical endonuclease involved in DNA repair and tumor suppression. Our previous study has shown reduced expression of Mus81 in hepatocellular carcinoma and its association with the metastastic potential and prognosis of hepatocellular carcinoma. However, the role of Mus81 in colorectal carcinoma is currently unknown. We therefore carried out the present study to explore the correlation between Mus81 expression and the progression of colorectal carcinoma. Mus81 expression in 92 cases of colorectal carcinoma and matched normal tissues was determined by quantitative real-time polymerase chain reaction. Our results showed that Mus81 expression in colorectal carcinoma tissues was significantly reduced compared with the corresponding normal tissues (P < 0.001) and the downregulation of Mus81 (decreased by more than 50%) was found in 60.9% (56/92) of colorectal carcinoma. Moreover, Mus81 downregulation correlated significantly to hepatic metastasis (P = 0.019) and a high TNM stage (P = 0.025) of colorectal carcinoma. In addition, the decrease of Mus81 was also detected in 10 cases of hepatic metastasis tissues compared with the corresponding primary colorectal carcinoma tissues (P = 0.016). More importantly, colorectal carcinoma patients with apparent Mus81 downregulation have shown significantly poorer overall survival than those with little Mus81 downregulation (P = 0.0374). Also, multivariable Cox regression analysis identified Mus81 downregulation as an independent prognostic factor for colorectal carcinoma (hazard ratio, 1.678; P = 0.040). In conclusion, the reduced expression of Mus81 is closely related to hepatic metastasis and poor prognosis of colorectal carcinoma, indicating Mus81 as a novel prognostic marker for colorectal carcinoma. (Cancer Sci 2011; 102: 472-477) C olorectal carcinoma (CRC) ranks as the third most common cancer in the world and the incidence of CRC is increasing rather rapidly in the Asia-Pacific region, especially in Japan.(1,2)Up until now, abundant evidence has shown that a variety of genetic and epigenetic alterations in both oncogenes and tumor suppressors are involved in the pathogenesis of CRC. Activation of oncogenes such as the ras gene and the inactivation of tumor suppressors such as APC and p53 genes have been documented in CRC. (3)(4)(5) In addition, we have identified some genetic as well as epigenetic changes related to this disease.(6-11) However, further investigations are still necessary to clarify the tumorigenic pathway of CRC.The Mus81 gene encodes a structure-specific DNA endonuclease, which resolves holliday junctions through constituting a heterodimer with Eme1 ⁄ Mms4 and plays a critical role in the repair of double-strand breaks of DNA and maintenance of chromosomal integrity.(12-15) McPherson et al. (16) have shown that 73% Mus81 ) ⁄ ) mice and 50% Mus81 + ⁄ ) mice died of various spontaneous tumors such as lymphoma, breast cancer and prostate cancer, implicating Mus81 as a potent tumor suppressor in mice. Moreover, Mus81 was found ...

This report presents the case of a 62-year-old man with a collision tumor of primary malignant lymphoma and adenocarcinoma in the cecum. All regional mesenteric lymph nodes that were removed surgically were found to be occupied by lymphoma cells and no lymph nodes contained any cancer cells, although the primary carcinomas did exhibit lymphatic invasion. Malignant lymphoma was also seen in the duodenum. Systemic chemotherapy was administered for the malignant lymphoma, and a complete response was thus obtained. However, just after chemotherapy multiple liver metastases of adenocarcinoma emerged, and chemotherapy against adenocarcinoma was therefore continued. The occurrence of synchronous lymphoma and adenocarcinoma of the colorectum is rare. Furthermore, collisions of these different entities are also extremely unusual; so far only five such case reports have been published. The accurate clinical determination of the dominant tumor and a close follow-up is required for proper treatment in these cases.

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