Mechanisms of primary and acquired resistance to PD-1/PD-L1 blockade and the emerging role of gut microbiome

The progress on the relationship between gut microbiota and immune checkpoint blockade in tumors

Immune checkpoint blockade (ICB) has emerged as a promising immunotherapeutic approach for the treatment of various tumors. However, the efficacy of this therapy is limited in a subset of patients, and it is important to develop strategies to enhance immune responses. Studies have demonstrated a critical role of gut microbiota in regulating the therapeutic response to ICB. Gut microbiota composition, diversity, and function are mediated by metabolites, such as short-chain fatty acids and secondary bile acids, that interact with host immune cells through specific receptors. In addition, gut bacteria may translocate to the tumor site and stimulate antitumor immune responses. Therefore, maintaining a healthy gut microbiota composition, for instance through avoiding the use of antibiotics or probiotic interventions, can be an effective approach to optimize ICB therapy. This review summarizes the current understanding of the microbiota-immunity interactions in the context of ICB therapy, and discusses potential clinical implications of these findings.

The role of gut microbiome in immune modulation in metastatic renal cell carcinoma

Treatment of metastatic renal cell carcinomas (mRCC) has drastically improved since the advent of immunotherapy with immune checkpoint inhibitors (ICIs), with a significant proportion of patients achieving durable responses. While this has revolutionized treatment and improved outcomes for mRCC patients, a large subset of patients still does not respond to treatment with ICIs. Moreover, ICIs can induce various immune-related adverse events, limiting their use in many patients. Therefore, there is a need to identify the predictive biomarkers of both efficacy and toxicity associated with ICIs, which would allow for a more personalized approach and help with clinical decision-making. This review aims to explore the role of the gut microbiome in RCC to overcome primary resistance and predict response to treatment with ICIs. First, current therapeutic strategies and mechanisms of action of ICI therapies for RCC treatment will be reviewed. With the technological development of shotgun whole-genome sequencing, the gut microbiome has emerged as an exciting field of research within oncology. Thus, the role of the microbiome and its bidirectional interaction with ICIs and other drugs will be explored, with a particular focus on the microbiome profile in RCC. Lastly, the rationale for future clinical interventions to overcome resistance to ICIs using fecal microbiota transplantation in patients with RCC will be presented.

Repurposing disulfiram as a chemo-therapeutic sensitizer: molecular targets and mechanisms

Currently, chemo-therapy is still the main strategy for cancer treatment. However, chemo-therapy resistance remains its main challenge. Disulfiram [DSF] is a drug approved by FDA for the treatment of alcohol addiction, but it is later discovered that it has the anticancer activity. Importantly, there have been many literatures reporting that DSF can be used as a chemo-therapeutic sensitizer to enhance the anticancer activity of chemo-drugs in a variety of cancers. Furthermore, the combinations of DSF and chemo-drugs have been tested in clinic trials. In the review, we summarized the possible molecular targets and mechanisms of DSF to reverse chemo-resistance. We also further discussed the opportunities and challenges of DSF as a chemo-therapeutic sensitizer. In conclusion, DSF could be a potential repurposed drug to sensitize cancer cells to chemo-therapy in clinic.

Acquired resistance for immune checkpoint inhibitors in cancer immunotherapy: challenges and prospects

Drug resistance has become an obstacle to the further development of immunotherapy in clinical applications and experimental studies. In the current review, the acquired resistance to immunotherapy was examined. The mechanisms of acquired resistance were based on three aspects as follows: The change of the tumor functions, the upregulated expression of inhibitory immune checkpoint proteins, and the effects of the tumor microenvironment. The combined use of immunotherapy and other therapies is performed to delay acquired resistance. A comprehensive understanding of acquired drug resistance may provide ideas for solving this dilemma.