Background: Bcl-xL plays an important role in tumors from different origins, including melanoma, and for this reason it has been widely targeted with small-molecule BH3 mimetics, which unfortunately show several adverse effects. To overcome this limitation, selective Bcl-xL proteolysis-targeting chimera degraders have been developed. Among these, DT2216, a candidate in phase I/II clinical trials, has demonstrated antitumoral activity in preclinical cancer models from different origins, not including melanoma.
Methods: By using several established and patient-derived BRAF wild type and mutated melanoma cells, we performed western blot analysis and MTT assay to study DT2216 effect on Bcl-xL protein levels and cell viability, respectively. Combination studies were performed on BRAF mutated melanoma cells treated with DT2216 and Dabrafenib/Trametinib or on wild type melanoma cells treated with DT2216 and Trametinib or S63845. Combination index was calculated to study drug interactions. Apoptotic induction was studied through western blot (PARP-1 cleavage), cytofluorimetric (subG1 peak in the cell cycle) and live-cell fluorescent imaging of activated caspases 3/7 analyses. Group differences were analysed with a two-sided paired or unpaired Student's t-test. To investigate the effect of the combination treatment in vivo, A375luc melanoma cells were inoculated in xenograft mice, then treated with Dabrafenib/Trametinib or DT2216, alone or in combination, for three weeks. Differences between groups, were analysed with Mann-Whitney test.
Results: DT2216 induced the specific and long-lasting degradation of Bcl-xL protein, and reduced cell viability, in a concentration-dependent manner. Of note, a positive correlation between Bcl-xL degradation and sensitivity to DT2216 was observed, being cells with higher degradation the most sensitive to DT2216. In combination studies, DT2216 was able to enhance the activity of target therapy regardless BRAF mutational status. Moreover, the Mcl-1 specific inhibitor, S63845, potentiated the efficacy of DT2216 in melanoma cells in which DT2216 determined an increase of Mcl-1 protein. Interestingly, DT2216 also increased the activity of target therapy in melanoma cells resistant to Dabrafenib and Trametinib. Finally, experiments in a xenograft mouse melanoma model highlighted DT2216 potentiating effect of target therapy, not only inducing a significant reduction of tumor growth, but also showing a longer disease control.
Conclusion: Our findings provide new insights for combination therapy including Bcl-xL degradation for melanoma treatment.
Background: N-acetyltransferase 10 (NAT10) mediated N4-acetylcytidine (ac4C) modification has been implicated in tumor progression; however, the precise role and underlying mechanism of NAT10 in breast cancer progression remain largely undefined.
Methods: The expression and prognostic significance of NAT10 in breast cancer were evaluated using clinical tissue samples and public databases. Functional assays were performed in vitro and in vivo to assess the effects of NAT10 on tumor growth and immune evasion. Mechanistic studies, including RNA immunoprecipitation (RIP), ac4C RNA immunoprecipitation (acRIP), and co-immunoprecipitation (Co-IP), were conducted to elucidate the interaction between NAT10 and histone deacetylase 4 (HDAC4) and their roles in regulating NF-κB signaling and programmed death-ligand 1 (PD-L1) expression.
Results: NAT10 expression was significantly upregulated in breast cancer and correlated with poor patient prognosis. NAT10 mediated ac4C modification enhanced the stability of HDAC4 mRNA, thereby promoting HDAC4 expression. Conversely, HDAC4 stabilized NAT10 protein through post-transcriptional deacetylation, forming a self-reinforcing regulatory loop. Elevated HDAC4 activated the NF-κB signaling pathway, resulting in increased PD-L1 transcription and enhanced immune evasion of breast cancer cells. Inhibition of the NAT10/HDAC4/NF-κB axis markedly reduced PD-L1 expression and restored antitumor immune responses.
Conclusion: Our findings identify a self-reinforcing NAT10/HDAC4 signaling circuit that drives breast cancer progression and immune evasion. Targeting NAT10 represents a promising therapeutic strategy to overcome immunosuppression and improve patient outcomes in breast cancer.
Background: Human papillomavirus (HPV) 16 infection is associated with several human malignancies. Developing therapeutic vaccines holds great potential for patients who do not benefit from standard care. Circular RNA (circRNA) is an emerging next-generation platform for cancer vaccine development owing to its superior stability and convenient manufacturing process. Herein, we report development of a synthetic circRNA encoding fused HPV16 E7/E6 antigens encapsulated with lipid nanoparticles (LNP) to treat HPV16-related solid tumors.
Methods: The immunogenicity and anti-tumor immune response of the LNP-circRNA vaccine was determined in naïve C57BL/6 mice and TC-1 tumor-bearing mice, respectively. Changes in immune cells were examined using flow cytometry and immunofluorescence assay. RNA sequencing was used to identify differentially expressed genes and changes in the tumor microenvironment (TME) of tumors treated with LNP-circRNAE7E6 and empty LNP. Anti-tumor efficacy was further evaluated in LNP-circRNAE7E6 vaccine combined with anti-PD-L1 antibody treatment.
Results: Prime-boost vaccination with LNP-circRNAE7E6 induced a large pool of functional antigen-specific cytotoxic T cells in both the peripheral blood and spleen. This immunization led to profound changes in the TME, characterized by the upregulation of immune activation genes, heavy infiltration of immune cells, and polarization toward a proinflammatory state. Consequently, circRNAE7E6 immunization could mediate complete tumor regression and prevent tumor growth. Moreover, vaccination sensitized non-inflamed tumors to immune checkpoint blockade therapy.
Conclusions: The present study results demonstrate that LNP-circRNAE7E6 vaccine is capable of eliciting robust anti-tumor immunity in the periphery and TME, highlighting the potential for treating HPV16-related cancers and preventing tumor recurrence.
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