Global S&T Development Trend Analysis Platform of Resources and Environment
Immune evasion is a major obstacle for cancer treatment. Common mechanisms of evasion include impaired antigen presentation caused by mutations or loss of heterozygosity of the major histocompatibility complex class I (MHC-I), which has been implicated in resistance to immune checkpoint blockade (ICB) therapy(1-3). However, in pancreatic ductal adenocarcinoma (PDAC), which is resistant to most therapies including ICB4, mutations that cause loss of MHC-I are rarely found(5) despite the frequent downregulation of MHC-I expression(6-8). Here we show that, in PDAC, MHC-I molecules are selectively targeted for lysosomal degradation by an autophagy-dependent mechanism that involves the autophagy cargo receptor NBR1. PDAC cells display reduced expression of MHC-I at the cell surface and instead demonstrate predominant localization within autophagosomes and lysosomes. Notably, inhibition of autophagy restores surface levels of MHC-I and leads to improved antigen presentation, enhanced anti-tumour T cell responses and reduced tumour growth in syngeneic host mice. Accordingly, the anti-tumour effects of autophagy inhibition are reversed by depleting CD8(+) T cells or reducing surface expression of MHC-I. Inhibition of autophagy, either genetically or pharmacologically with chloroquine, synergizes with dual ICB therapy (anti-PD1 and anti-CTLA4 antibodies), and leads to an enhanced anti-tumour immune response. Our findings demonstrate a role for enhanced autophagy or lysosome function in immune evasion by selective targeting of MHC-I molecules for degradation, and provide a rationale for the combination of autophagy inhibition and dual ICB therapy as a therapeutic strategy against PDAC.
Inhibition of the autophagy-lysosome system upregulates surface expression of MHC class I proteins and enhances antigen presentation, and evokes a potent anti-tumour immune response that is mediated by CD8(+) T cells.
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
Elucidating elementary mechanisms that underlie bacterial diversity is central to ecology(1,2) and microbiome research(3). Bacteria are known to coexist by metabolic specialization(4), cooperation(5) and cyclic warfare(6-8). Many species are also motile(9), which is studied in terms of mechanism(10,11), benefit(12,13), strategy(14,15), evolution(16,17) and ecology(18,19). Indeed, bacteria often compete for nutrient patches that become available periodically or by random disturbances(2,20,21). However, the role of bacterial motility in coexistence remains unexplored experimentally. Here we show that-for mixed bacterial populations that colonize nutrient patches-either population outcompetes the other when low in relative abundance. This inversion of the competitive hierarchy is caused by active segregation and spatial exclusion within the patch: a small fast-moving population can outcompete a large fast-growing population by impeding its migration into the patch, while a small fast-growing population can outcompete a large fast-moving population by expelling it from the initial contact area. The resulting spatial segregation is lost for weak growth-migration trade-offs and a lack of virgin space, but is robust to population ratio, density and chemotactic ability, and is observed in both laboratory and wild strains. These findings show that motility differences and their trade-offs with growth are sufficient to promote diversity, and suggest previously undescribed roles for motility in niche formation and collective expulsion-containment strategies beyond individual search and survival.
In mixed bacterial populations that colonize nutrient patches, a growth-migration trade-off can lead to spatial exclusion that provides an advantage to populations that become rare, thereby stabilizing the community.
