DRO1/CCDC80: a Novel Tumor Suppressor of Colorectal Carcinogenesis

Oncogenes and tumor suppressor genes: functions and roles in cancers

Cancer, being the most formidable ailment, has had a profound impact on the human health. The disease is primarily associated with genetic mutations that impact oncogenes and tumor suppressor genes (TSGs). Recently, growing evidence have shown that X-linked TSGs have specific role in cancer progression and metastasis as well. Interestingly, our genome harbors around substantial portion of genes that function as tumor suppressors, and the X chromosome alone harbors a considerable number of TSGs. The scenario becomes even more compelling as X-linked TSGs are adaptive to key epigenetic processes such as X chromosome inactivation. Therefore, delineating the new paradigm related to X-linked TSGs, for instance, their crosstalk with autosome and involvement in cancer initiation, progression, and metastasis becomes utmost importance. Considering this, herein, we present a comprehensive discussion of X-linked TSG dysregulation in various cancers as a consequence of genetic variations and epigenetic alterations. In addition, the dynamic role of X-linked TSGs in sex chromosome-autosome crosstalk in cancer genome remodeling is being explored thoroughly. Besides, the functional roles of ncRNAs, role of X-linked TSG in immunomodulation and in gender-based cancer disparities has also been highlighted. Overall, the focal idea of the present article is to recapitulate the findings on X-linked TSG regulation in the cancer landscape and to redefine their role toward improving cancer treatment strategies.

Loss of DRO1/CCDC80 in the tumor microenvironment promotes carcinogenesis

Tumors are composed of the tumor cells and the surrounding microenvironment. Both are closely interwoven and interact by a complex and multifaceted cross-talk which plays an integral part in tumor initiation, growth, and progression. Dro1/Ccdc80 has been shown to be a potent suppressor of colorectal cancer and ubiquitous inactivation of Dro1/Ccdc80 strongly promoted colorectal carcinogenesis in Apc^Min/+ mice and in a chemically-induced colorectal cancer model.

The aim of the present study was to investigate whether Dro1/Ccdc80’s tumor suppressive function is tumor-cell-autonomous. Expression of Dro1/Ccdc80 in cancer cells had no effect on both colon tumor development in Apc^Min/+ mice and formation of xenograft tumors. In contrast, DRO1/CCDC80 loss in the microenvironment strongly increased tumor growth in xenograft models, inhibited cancer cell apoptosis, and promoted intestinal epithelial cell migration. Moreover, stromal Dro1/Ccdc80 inactivation facilitated formation of intestinal epithelial organoids. Expression analyses showed Dro1/Ccdc80 to be significantly down-regulated in murine gastric cancer associated fibroblasts, in Apc^Min/+ colon tumor primary stromal cells and in microdissected stroma from human colorectal cancer compared to normal, non-tumor stroma. Our results demonstrate epithelial derived DRO1/CCDC80 to be dispensable for intestinal tissue homeostasis and identify Dro1/Ccdc80 as tumor suppressor in the tumor microenvironment.