Long-Term Gemcitabine Treatment Reshapes the Pancreatic Tumor Microenvironment and Sensitizes Murine Carcinoma to Combination Immunotherapy

Pancreatic ductal adenocarcinoma (PDAC) is a leading cause of cancer-related death with a median survival time of 6–12 months. Most patients present with disseminated disease and the majority are offered palliative chemotherapy. With no approved treatment modalities for patients who progress on chemotherapy, we explored the effects of long-term Gemcitabine on the tumor microenvironment in order to identify potential therapeutic options for chemo-refractory PDAC. Using a combination of mouse models, primary cell line-derived xenografts, and established tumor cell lines, we first evaluated chemotherapy-induced alterations in the tumor secretome and immune surface proteins by high throughput proteomic arrays. In addition to enhancing antigen presentation and immune checkpoint expression, Gemcitabine consistently increased the synthesis of CCL/CXCL chemokines and TGFβ-associated signals. These secreted factors altered the composition of the tumor stroma, conferring Gemcitabine resistance to cancer-associated fibroblasts in vitro and further enhancing TGFβ1 biosynthesis. Combined Gemcitabine and anti-PD-1 treatment in transgenic models of murine PDAC failed to alter disease course unless mice also underwent genetic or pharmacologic ablation of TGFβ signaling. In the setting of TGFβ signaling deficiency, Gemcitabine and anti-PD-1 led to a robust CD8+ T-cell response and decrease in tumor burden, markedly enhancing overall survival. These results suggest that Gemcitabine successfully primes PDAC tumors for immune checkpoint inhibition by enhancing antigen presentation only following disruption of the immunosuppressive cytokine barrier. Given the current lack of third-line treatment options, this approach warrants consideration in the clinical management of Gemcitabine-refractory PDAC

Uridine Ameliorates Dextran Sulfate Sodium (DSS)-Induced Colitis in Mice

Uridine, one of the four components that comprise RNA, has attracted attention as a novel therapeutic modulator of inflammation. However, very little is known about its effect on intestinal inflammation. The aim of the present study was to investigate the potential protective effect of intracolonic administered uridine against DSS induced colitis in male C57BL/6 mice. Intracolonic instillation of 3 doses of uridine 1 mg/Kg (lower dose), 5 mg/Kg (medium dose), and 10 mg/Kg (higher dose) in saline was performed daily. Uridine at medium and high dose significantly reduced the severity of colitis (DAI score) and alleviated the macroscopic and microscopic signs of the disease. The levels of proinflammatory cytokines IL-6, IL-1 beta and TNF in serum as well as mRNA expression in colon were significantly reduced in the uridine treated groups. Moreover, colon tissue myloperoxidase activities, protein expression of IL-6, TNF-alpha, COX-2, P-NFkB and P-Ikk-alpha beta in the colon tissues were significantly reduced in medium and high dose groups. These findings demonstrated that local administration of uridine alleviated experimental colitis in male C57BL/6 mice accompanied by the inhibition of neutrophil infiltration and NF-kappa B signaling. Thus, Uridine may be a promising candidate for future use in the treatment of inflammatory bowel disease.Funding Agencies|County Council of Ostergotland, Sweden</p

Using proteolysis-targeting chimera technology to reduce navitoclax platelet toxicity and improve its senolytic activity.

Small molecules that selectively kill senescent cells (SCs), termed senolytics, have the potential to prevent and treat various age-related diseases and extend healthspan. The use of Bcl-xl inhibitors as senolytics is largely limited by their on-target and dose-limiting platelet toxicity. Here, we report the use of proteolysis-targeting chimera (PROTAC) technology to reduce the platelet toxicity of navitoclax (also known as ABT263), a Bcl-2 and Bcl-xl dual inhibitor, by converting it into PZ15227 (PZ), a Bcl-xl PROTAC, which targets Bcl-xl to the cereblon (CRBN) E3 ligase for degradation. Compared to ABT263, PZ is less toxic to platelets, but equally or slightly more potent against SCs because CRBN is poorly expressed in platelets. PZ effectively clears SCs and rejuvenates tissue stem and progenitor cells in naturally aged mice without causing severe thrombocytopenia. With further improvement, Bcl-xl PROTACs have the potential to become safer and more potent senolytic agents than Bcl-xl inhibitors