Melanoma microenvironment reprogramming by intralesional Mycobacterium bovis Bacillus Calmette-Guérin (BCG) therapy fosters antitumor T cell responses

LEE AGNES F; SIELING PETER; CHAN ALFRED; FARIES, MARK; LARDONE RICARDO D; FOSHAG LELAND; LEE, DELPHINE J

Buenos Aires

Congreso; Reunion Conjunta de Sociedades de Biociencias; 2017

SOCIEDAD ARGENTINA DE INVESTIGACIÓN CLÍNICA (SAIC), SOCIEDAD ARGENTINA DE INVESTIGACIÓN BIOQUÍMICA Y BIOLOGÍA MOLECULAR (SAIB), SOCIEDAD ARGENTINA DE INMUNOLOGÍA (SAI),

Inoperable cutaneous metastatic melanoma (CMM) has been treated for decades with intralesional Mycobacterium bovis bacillus Calmette?Guérin (BCG), a relatively inexpensive therapy. However, skin mechanisms of intralesional BCG used in this manner persist understudied. Tumor-associated macrophages (M2) infiltrate melanomas and impair antitumor immunity. Since macrophages play a pivotal role against both cancer and mycobacterial infections, we hypothesized BCG regulates macrophages to promote antitumor immunity. The analysis of intralesional BCG-treated CMM lesions, in combination with in vitro studies, allowed us to further investigate BCG-altered pathways. BCG-treated, in vitro-polarized M2 (M2-BCG) showed transcriptional changes enriched for inflammation, immune cell recruitment, cross talk, and activation pathways. Mechanistic network analysis revealed M2-BCG potential to improve interferon gamma (IFN-γ) responses. Consistent with this finding, frequency of IFN-γ-producing CD4+ T cells responding to M2-BCG vs. mock-treated M2 increased (p < 0.05). Moreover, conditioned media from M2-BCG vs. M2 elevated the frequency of granzyme B-producing CD8+ tumor-infiltrating lymphocytes (TILs) challenged with autologous melanoma cell lines (p < 0.01). These enhancements were also observed for cells or conditioned media from BCG-treated, in vitro-polarized M1 macrophage cultures (M1-BCG, p < 0.05). When comparing transcriptomes of intralesional BCG-injected CMM with uninjected lesions we found enrichment for immune functions, with the most prevalent pathways representing T cell activation mechanisms. In vitro-infected, MM-derived cell lines induced higher frequency of IFN-γ-producing TIL from the same melanoma (p < 0.05). Our data hints toward BCG favoring antitumor responses in CMM through direct/indirect effects on tumor microenvironment components including macrophages, T cells, and tumor cells.