6q24.3

CAPOK,DUH1,SH3D6A,dJ323M4.1

Breast cancer

Loss of the gene-internal microsatellite DNA marker D6S311 was found in 30% of samples of primary breast carcinoma, and the LOH was significantly correlated with poor survival and increase in tumor size. In established human mammary cancer cell lines, SASH1 is expressed at relatively low levels. SASH1 is downregulated in the majority (74%) of breast tumors in comparison with corresponding normal breast epithelia. In addition, SASH1 is also downregulated in tumors of the lung and thyroid. (Zeller et al., 2003).

Colorectal cancer

The mRNA as well as protein expression of SASH1 was strongly and significantly reduced in colon cancer of UICC stage II, III, and IV, as well as in colorectal liver metastases. In contrast, SASH1 expression was not significantly altered in benign adenomas and in early stage lesions (UICC I). Around 40% of primary colon tumours tested (n=113) showed a 10-fold or stronger reduction in SASH1 expression, compared to normal colon mucosa. Decreased SASH1 mRNA expression was correlated with the occurrence of metachronous distant metastasis, and multivariate analysis identified SASH1 downregulation as an independent negative prognostic parameter for patient survival (Rimkus et al., 2006). Recently, these results were confirmed on an independent patient collective of stage II colon cancer (n=179 patients), confirming that decreased SASH1 expression is an independent negative prognostic factor in colon cancer, allowing to distinguish high-risk patients in early, locally restriced stages of the disease (Nitsche et al., 2012).

Pancreatic cancer (unpublished observations)

In a collective of n=103 patients with pancreatic ductal adenocarcinoma, 38% of the tumors showed no or strongly reduced SASH1 protein expression by immunohistochemistry. Decreased SASH1 expression was significantly reduced with poor survival in Kaplan-Meier analysis (Tiago de Oliveira and Klaus-Peter Janssen, unpublished data).

Benign dyskeratosis

SASH1 germline mutations have been identified in patients with a kind of dyschromatosis. Of note, three independent heterozygous germline mutations have been identified, that cause amino acid substitutions in the central SH3/SAM-containing region in the SASH1 gene. In epidermal tissues from an affected individual, increased transepithelial migration of melanocytes was observed (Zhou et al., 2013).

SASH1 protein was significantly down-regulated in osteosarcoma tissues compared to normal bone tissue. Moreover, SASH1 protein showed significant down-regulation in osteosarcoma tissues from patients with lung metastasis compared to those without lung metastasis, and, lastly, a gradual decrease of SASH1 expression occurred with increasing Enneking stage (Meng et al., 2013).