Cutting Edge: The Expression of Transcription Inhibitor GFI1 Is Induced by Retinoic Acid to Rein in Th9 Polarization.

IL-9, produced mainly by specialized T cells, mast cells, and group 2 innate lymphoid cells, regulates immune responses, including anti-helminth and allergic responses. Polarization of naive CD4 T cells into IL-9-producing T cells (Th9s) is induced by IL-4 and TGF-ß1 or IL-1ß. In this article, we report that the transcription factor growth factor-independent 1 transcriptional repressor (GFI1) plays a negative role in mouse Th9 polarization. Moreover, the expression of GFI1 is controlled by liganded RARα, allowing GFI1 to mediate the negative effect of retinoic acid on IL-9 expression. The Gfi1 gene has multiple RARα binding sites in the promoter region for recruiting nuclear coactivator steroid receptor coactivator-3 and p300 for histone epigenetic modifications in a retinoic acid-dependent manner. Retinoic acid-induced GFI1 binds the Il9 gene and suppresses its expression. Thus, GFI1 is a novel negative regulator of Il9 gene expression. The negative GFI1 pathway for IL-9 regulation provides a potential control point for Th9 activity.

Clinically Relevant Humanized Mouse Models of Metastatic Prostate Cancer Facilitate Therapeutic Evaluation.

There is tremendous need for improved prostate cancer models. Anatomically and developmentally, the mouse prostate differs from the human prostate and does not form tumors spontaneously. Genetically engineered mouse models lack the heterogeneity of human cancer and rarely establish metastatic growth. Human xenografts are an alternative but must rely on an immunocompromised host. Therefore, we generated prostate cancer murine xenograft models with an intact human immune system (huNOG and huNOG-EXL mice) to test whether humanizing tumor-immune interactions would improve modeling of metastatic prostate cancer and the impact of androgen receptor-targeted and immunotherapies. These mice maintain multiple human immune cell lineages, including functional human T-cells and myeloid cells. Implications: To the best of our knowledge, results illustrate the first model of human prostate cancer that has an intact human immune system, metastasizes to clinically relevant locations, responds appropriately to standard-of-care hormonal therapies, and can model both an immunosuppressive and checkpoint-inhibition responsive immune microenvironment.

Clinically relevant humanized mouse models of metastatic prostate cancer to evaluate cancer therapies.

There is tremendous need for improved prostate cancer (PCa) models. The mouse prostate does not spontaneously form tumors and is anatomically and developmentally different from the human prostate. Engineered mouse models lack the heterogeneity of human cancer and rarely establish metastatic growth. Human xenografts represent an alternative but rely on an immunocompromised host. Accordingly, we generated PCa murine xenograft models with an intact human immune system (huNOG and huNOG-EXL mice) to test whether humanizing tumor-immune interactions would improve modeling of metastatic PCa and the impact of hormonal and immunotherapies. These mice maintain multiple human cell lineages, including functional human T-cells and myeloid cells. In 22Rv1 xenografts, subcutaneous tumor size was not significantly altered across conditions; however, metastasis to secondary sites differed in castrate huNOG vs background-matched immunocompromised mice treated with enzalutamide (enza). VCaP xenograft tumors showed decreases in growth with enza and anti-Programed-Death-1 treatments in huNOG mice, and no effect was seen with treatment in NOG mice. Enza responses in huNOG and NOG mice were distinct and associated with increased T-cells within tumors of enza treated huNOG mice, and increased T-cell activation. In huNOG-EXL mice, which support human myeloid development, there was a strong population of immunosuppressive regulatory T-cells and Myeloid-Derived-Suppressor-Cells (MDSCs), and enza treatment showed no difference in metastasis. Results illustrate, to our knowledge, the first model of human PCa that metastasizes to clinically relevant locations, has an intact human immune system, responds appropriately to standard-of-care hormonal therapies, and can model both an immunosuppressive and checkpoint-inhibition responsive immune microenvironment.

Deficiency in mammalian STN1 promotes colon cancer development via inhibiting DNA repair.

Despite the high lethality of colorectal cancers (CRCs), only a limited number of genetic risk factors are identified. The mammalian ssDNA-binding protein complex CTC1-STN1-TEN1 protects genome stability, yet its role in tumorigenesis is unknown. Here, we show that attenuated CTC1/STN1 expression is common in CRCs. We generated an inducible STN1 knockout mouse model and found that STN1 deficiency in young adult mice increased CRC incidence, tumor size, and tumor load. CRC tumors exhibited enhanced proliferation, reduced apoptosis, and elevated DNA damage and replication stress. We found that STN1 deficiency down-regulated multiple DNA glycosylases, resulting in defective base excision repair (BER) and accumulation of oxidative damage. Collectively, this study identifies STN1 deficiency as a risk factor for CRC and implicates the previously unknown STN1-BER axis in protecting colon tissues from oxidative damage, therefore providing insights into the CRC tumor-suppressing mechanism.