miR-181a promotes multiple pro-tumorigenic functions through targeting TGFβR3

Cutaneous squamous cell carcinoma (cuSCC) comprises 15-20% of all skin cancers and has a well-defined progression sequence from precancerous actinic keratosis (AK), to invasive cuSCC. In order to identify targets for chemoprevention, we previously reported a cross-species analysis to identify transcriptional drivers of cuSCC development and identified miR-181a as a potential oncomiR. We show that upregulation of miR-181a promotes multiple pro-tumorigenic properties by targeting an understudied component of TGFβ signaling, TGFβR3. miR-181a and TGFβR3 are upregulated and downregulated, respectively, in cuSCC. miR-181a overexpression (OE) and TGFβR3 knockdown (KD) significantly suppresses UV-induced apoptosis in HaCaT cells and in primary normal human epidermal keratinocytes (NHEK). In addition, OE of miR-181a or KD of TGFβR3 by shRNA enhances anchorage-independent survival. miR-181a OE or TGFβR3 KD enhances cellular migration and invasion and upregulation of EMT markers. Luciferase reporter assays demonstrate that miR-181a directly targets the 3'UTR of TGFβR3. miR-181a upregulates pSMAD3 levels following TGFβ2 administration and results in elevated SNAIL and SLUG expression. Finally, we confirm in-vivo, that miR-181a inhibition compromises tumor growth. Importantly, these phenotypes can be reversed with TGFβR3 OE or KD in the context of miR-181a OE or KD, respectively, further highlighting the physiologic relevance of this regulation in cuSCC.

Apigenin Increases SHIP-1 Expression, Promotes Tumoricidal Macrophages and Anti-Tumor Immune Responses in Murine Pancreatic Cancer

Pancreatic cancer (PC) has an extremely poor prognosis due to the expansion of immunosuppressive myeloid-derived suppressor cells (MDSC) and tumor-associated macrophages (TAM) in the inflammatory tumor microenvironment (TME), which halts the recruitment of effector immune cells and renders immunotherapy ineffective. Thus, the identification of new molecular targets that can modulate the immunosuppressive TME is warranted for PC intervention. Src Homology-2 (SH2) domain-containing Inositol 5'-Phosphatase-1 (SHIP-1) is a lipid signaling protein and a regulator of myeloid cell development and function. Herein, we used the bioflavonoid apigenin (API) to reduce inflammation in different PC models. Wild type mice harboring heterotopic or orthotopic PC were treated with API, which induced SHIP-1 expression, reduced inflammatory tumor-derived factors (TDF), increased the proportion of tumoricidal macrophages and enhanced anti-tumor immune responses, resulting in a reduction in tumor burden compared to vehicle-treated PC mice. In contrast, SHIP-1-deficient mice exhibited an increased tumor burden and displayed augmented proportions of pro-tumor macrophages. These results provide further support for the importance of SHIP-1 expression in promoting pro-tumor macrophage development in the pancreatic TME. Our findings suggest that agents augmenting SHIP-1 expression may provide novel therapeutic options for the treatment of PC.

PD-L1/PD-1 Immunotherapy Modulates Effector T Cells Homeostasis and Function in Murine Pancreatic Cancer

Pancreatic Cancer (PC) is one of the most aggressive and deadliest types of cancer, and it is projected to be the second leading cause of cancer-related deaths in the U.S. by the year 2030.

PC evades immune surveillance by disrupting the immune homeostasis of effector T cells (Teff). T cells homeostasis is critical for proper anti-tumor immune responses. Preliminary flow cytometry data revealed that murine pancreatic (Panc02) cancer cells produce inflammatory soluble factors and in addition, express Major Histocompatibility Complex class I (MHC-I) and Programmed Death Ligand 1 (PD-L1) and 2 (PD-L2). PD-L1/2 can bind to PD-1 receptors on Teff and induce apoptosis or anergy, dampening the anti-tumor immunity. Cytokine bead array and flow cytometry analysis of serum from peripheral blood from C57BL/6 mice injected with Panc02 cells (TB mice) showed a significant increase in inflammatory factors compared to Control (CTRL) mice. Additionally, Teff from splenocytes from TB mice showed significant reduction in Teff percentages compared to CTRL mice, in vitro. In this study, CD3+ cells from CTRL mice were co-incubated with Panc02 cells pre-treated with anti-PD-L1 antibody (ab) to evaluate the modulation of Teff and cytokines production, in vitro. Mice were inoculated with the Panc02 pre-treated cells with anti-PD-L1 ab, to evaluate the modulation of Teff and cytokines production, in vivo. The results from this project may lead to the identification of new immunotherapeutic strategies to stabilize Teff homeostasis and function that could increase anti-tumor immune responses and combat PC progression.