BCG hydrogel promotes CTSS-mediated antigen processing and presentation, thereby suppressing metastasis and prolonging survival in melanoma

Abstract

BackgroundThe use of intralesional Mycobacterium bovis BCG (intralesional live BCG) for the treatment of metastatic melanoma resulted in regression of directly injected, and occasionally of distal lesions. However, intralesional-BCG is less effective in patients with visceral metastases and did not significantly improve overall survival.MethodsWe generated a novel BCG lysate and developed it into a thermosensitive PLGA-PEG-PLGA hydrogel (BCG hydrogel), which was injected adjacent to the tumor to assess its antitumor effect in syngeneic tumor models (B16F10, MC38). The effect of BCG hydrogel treatment on contralateral tumors, lung metastases, and survival was assessed to evaluate systemic long-term efficacy. Gene expression profiles of tumor-infiltrating immune cells and of tumor-draining lymph nodes from BCG hydrogel-treated mice were analyzed by single-cell RNA sequencing (scRNA-seq) and CD8+ T cell receptor (TCR) repertoire diversity was assessed by TCR-sequencing. To confirm the mechanistic findings, RNA-seq data of biopsies obtained from in-transit cutaneous metastases of patients with melanoma who had received intralesional-BCG therapy were analyzed.ResultsHere, we show that BCG lysate exhibits enhanced antitumor efficacy compared to live mycobacteria and promotes a proinflammatory tumor microenvironment and M1 macrophage (MΦ) polarization in vivo. The underlying mechanisms of BCG lysate-mediated tumor immunity are dependent on MΦ and dendritic cells (DCs). BCG hydrogel treatment induced systemic immunity in melanoma-bearing mice with suppression of lung metastases and improved survival. Furthermore, BCG hydrogel promoted cathepsin S (CTSS) activity in MΦ and DCs, resulting in enhanced antigen processing and presentation of tumor-associated antigens. Finally, BCG hydrogel treatment was associated with increased frequencies of melanoma-reactive CD8+ T cells. In human patients with melanoma, intralesional-BCG treatment was associated with enhanced M1 MΦ, mature DC, antigen processing and presentation, as well as with increased CTSS expression which positively correlated with patient survival.ConclusionsThese findings provide mechanistic insights as well as rationale for the clinical translation of BCG hydrogel as cancer immunotherapy to overcome the current limitations of immunotherapies for the treatment of patients with melanoma.

Distinct mechanisms of dysfunctional antigen‐presenting DCs and monocytes by single‐cell sequencing in multiple myeloma

“…Although earlier studies had confirmed that IRF1 regulates the endogenous expression of cathepsin S(CTSS), 22,23 there is no proof that the IRF1‐mediated CTSS pathway regulates antigen presentation. Nevertheless, DC maturation and antigen processing and presentation are ascribed to the regulation of CTSS in earlier studies 43 . Our data showed that downregulated IRF1 resulted in the decreased expression of CTSS in cDC2 and eventually suppressed the activation of CD4 + T cells.…”

Regulator of G-protein signaling 1 critically supports CD8+ TRM cell-mediated intestinal immunity

“…Heatmaps, correlation plots, and principal component analysis plots were created in R Studio (Rstudio Inc., Boston, USA). Gene expression data were generated with Nanostring arrays or retrieved from the indicated, pre-existing, open-access RNA sequencing data sets ( 31 , 32 ).…”

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“…BCG can be injected directly into the lungs to stimulate an immune response against cancer cells. It can be administered alone or in conjunction with other therapies, such as chemotherapy or radiation therapy ( 355 ).…”