Harnessing SHP2-targeted signaling to reinforce anti-tumor immune responses

Background: SHP2, a non-receptor protein tyrosine phosphatase, regulates both immune checkpoint signaling via PD-1 and oncogenic RAS/MAPK pathways, making it a promising target for integrated anti-cancer therapy. While SHP2 inhibitors have been primarily investigated for their tumor-intrinsic effects, their immunomodulatory potential remains unclear. Therefore, we investigated whether SHP2 inhibition can simultaneously relieve PD-1-mediated T cell suppression and inhibit tumor-intrinsic MAPK signaling, a dual-action mechanism particularly for tumors driven by RAS/MAPK signaling. Methods: Primary murine T cells and human Jurkat T cell lines were used to assess the immune cell responses. Flow cytometry was performed to characterize T cell activation, and cell viability was quantified using WST-1 and CellTiter-Glo assays. T cell-mediated cytotoxicity against cancer cells was evaluated by the LDH release assay. qPCR was conducted to analyze the gene expression profiles related to immune activation. To assess the impact on oncogenic signaling, RAS/MAPK pathway activity was measured by western blotting. For in vivo evaluation, mice bearing MC38-OVA syngeneic tumors received oral SHP2 inhibitor TNO155 (10 or 20 mg/kg, BID for 14 days). Results: Pharmacological inhibition of SHP2 using TNO155 (1 nM-10 µM) did not affect T cell viability, indicating its suitability for in vitro immunological analysis. Despite its minimal cytotoxicity, SHP2 inhibition significantly modulated T cell activation. Flow cytometric analysis revealed the upregulation of activation markers, including CD69 and Granzyme B expression, alongside enhanced T cell-mediated cytotoxicity against tumor cells, as measured by LDH release assay (increase of 20.9% cytotoxicity at 1 µM TNO155; P < 0.05). In syngeneic tumor-bearing immunocompetent mice, oral administration of TNO155 (p.o. BID) led to a significant reduction in tumor volume compared to vehicle-treated controls (tumor growth inhibition: 39.6% (10 mg/kg; P < 0.05) and 62.4% (20 mg/kg; P < 0.01) on day 14. Immunohistochemical and flow cytometric analyses detected the infiltration of CD8⁺ tumor-infiltrating lymphocytes, and qPCR revealed elevated expression of IFNgamma-responsive genes, including Cd274 (~2.2-fold induction; P < 0.001 ) in tumors. Notably, intratumoral CD8⁺ T cells exhibited enhanced effector function, with a marked increase in Granzyme B⁺ cells (control: 4.46 ± 1.86%; TNO155: 18.94 ± 12.27; P < 0.05 ) and a decrease in exhaustion markers TIM-3 and LAG-3. Conclusions: These findings demonstrate that SHP2 inhibition enhances anti-tumor immune responses and supports its potential as a dual-function therapeutic strategy in cancer immunotherapy. This study provides a robust preclinical foundation for the translational development of SHP2-targeted approaches in precision oncology.