The human transcriptome contains thousands of small open reading frames (sORFs) that encode microproteins whose functions remain largely unexplored. Here, we show that TINCR lncRNA encodes pTINCR, an evolutionary conserved ubiquitin-like protein (UBL) expressed in many epithelia and upregulated upon differentiation and under cellular stress. By gain- and loss-of-function studies, we demonstrate that pTINCR is a key inducer of epithelial differentiation in vitro and in vivo. Interestingly, low expression of TINCR associates with worse prognosis in several epithelial cancers, and pTINCR overexpression reduces malignancy in patient-derived xenografts. At the molecular level, pTINCR binds to SUMO through its SUMO interacting motif (SIM) and to CDC42, a Rho-GTPase critical for actin cytoskeleton remodeling and epithelial differentiation. Moreover, pTINCR increases CDC42 SUMOylation and promotes its activation, triggering a pro-differentiation cascade. Our findings suggest that the microproteome is a source of new regulators of cell identity relevant for cancer.

Vulvar cancer is rare and accounts for only 5% of all gynecologic cancers. Squamous cell carcinoma is the most common and makes up 90% of the cases. Vulvar adenocarcinoma usually arises in Bartholin and other vulvar glands. Primary vulvar intestinal-type adenocarcinoma is an extremely rare disease with an unclear prognosis and treatment. Its origin is still unknown, the most accepted theory suggests cloacal remnants as the source of origin. Only a few cases have been reported in the literature. We present a case of a 66-yr-old female who presented with vulvar pruritus and local discomfort, showing a 2 cm tumor located in the left labium minor in the region of vulvar fourchette. Wide vulvar excision and bilateral lymph nodes dissection were performed. Other concomitant lesions and distant extension of tumor were ruled out by positron emission tomography. Pathologic study revealed a colonic-type adenocarcinoma with typical villoglandular architecture with an irregular glandular structure composed of atypical columnar epithelium. The lesion had direct contact with epidermal surface and mainly was external without involving the dermis. Immunohistochemical analysis revealed positive staining for cytokeratin 20 and CDX2. p16 showed an abnormal diffuse and strong immunoexpression. The presence of a low-risk human papillomavirus was detected by polymerase chain reaction, therefore, the expression of p16 cannot be explained in this case by the presence of human papillomavirus. Additional studies are needed in additional cases to clarify the role of human papillomavirus in this kind of tumor.