Mitigating the prevalence and function of myeloid-derived suppressor cells by redirecting myeloid differentiation using a novel immune modulator

The lymphocyte-to-monocyte ratio as a significant inflammatory marker associated with survival of patients with metastatic renal cell carcinoma treated using nivolumab plus ipilimumab therapy

BACKGROUND

Nivolumab plus ipilimumab (NIVO + IPI) is the first-line treatment for patients with metastatic renal cell carcinoma (mRCC). While approximately 40% of patients treated with NIVO + IPI achieve a durable response, 20% develop primary resistance with severe consequences. Therefore, there is a clinical need for criteria to select patients suitable for NIVO + IPI therapy to optimize its therapeutic efficacy. Accordingly, our aim was to evaluate the association between candidate biomarkers measured before treatment initiation and survival.

METHODS

This was a multi-institutional, retrospective, cohort study of 183 patients with mRCC treated with systematic therapies between August 2015 and July 2023. Of these, 112 received NIVO + IPI as first-line therapy: mean age, 68 years; men, 83.0% (n = 93), and clear cell histology, 80.4% (n = 90). Univariable and multivariable analyses were used to evaluate associations between biomarkers and survival.

RESULTS

On univariate analysis, high C-reactive protein and systemic index, a high neutrophil-to-lymphocyte and platelet-to-lymphocyte ratio, and a low lymphocyte-to-monocyte ratio (LMR) were associated with shorter overall survival (OS). On multivariable analysis, a LMR ≤ 3 was retained as an independent factor associated to shorter OS with the highest accuracy (C-index, 0.656; hazard ratio, 7.042; 95% confidence interval, 2.0-25.0; p = 0.002).

CONCLUSION

A low LMR may identify patients who would be candidate for NIVO + IPI therapy for mRCC.

Reciprocal relationship between cancer stem cells and myeloid-derived suppressor cells: implications for tumor progression and therapeutic strategies

Recently, there has been an increased focus on cancer stem cells (CSCs) due to their resilience, making them difficult to eradicate. This resilience often leads to tumor recurrence and metastasis. CSCs adeptly manipulate their surroundings to create an environment conducive to their survival. In this environment, myeloid-derived suppressor cells (MDSCs) play a crucial role in promoting epithelial-mesenchymal transition and bolstering CSCs' stemness. In response, CSCs attract MDSCs, enhancing their infiltration, expansion and immunosuppressive capabilities. This interaction between CSCs and MDSCs increases the difficulty of antitumor therapy. In this paper, we discuss the interplay between CSCs and MDSCs based on current research and highlight recent therapeutic strategies targeting either CSCs or MDSCs that show promise in achieving effective antitumor outcomes.

A Bacterial and Ganglioside-based Nanoparticle Initiates Reprogramming of Macrophages and Promotes Antitumor Phenotypes

Macrophages represent the most abundant immune component of the tumor microenvironment and often exhibit protumorigenic (M2-like) phenotypes that contribute to disease progression. Despite their generally accepted protumorigenic role, macrophages can also display tumoricidal (or M1-like) behavior, revealing that macrophages can be functionally reprogrammed, depending on the cues received within the tumor microenvironment. Moreover, such plasticity may be achieved by pharmacologic or biologic interventions. To that end, we previously demonstrated that a novel immunomodulator termed the "very small size particle" (VSSP) facilitates maturation of dendritic cells and differentiation of myeloid-derived suppressor cells to APCs with reduced suppressive activity in cancer models. VSSP was further shown to act in the bone marrow to drive the differentiation of progenitors toward monocytes, macrophages, and dendritic cells during emergency myelopoiesis. However, the underlying mechanisms for VSSP-driven alterations in myeloid differentiation and function remained unclear. In this study, in mouse models, we focused on macrophages and tested the hypothesis that VSSP drives macrophages toward M1-like functional states via IRF8- and PU.1-dependent mechanisms. We further hypothesized that such VSSP-mediated actions would be accompanied by enhanced antitumor responses. Overall, we showed that (1) VSSP drives naive or M2-derived macrophages to M1-like states, (2) the M1-like state induced by VSSP occurs via IRF8- and PU.1-dependent mechanisms, and (3) single-agent VSSP induces an antitumor response that is accompanied by alterations in the intratumoral myeloid compartment. These results provide a deeper mechanistic underpinning of VSSP and strengthen its use to drive M1-like responses in host defense, including cancer.

Targeting myeloid-derived suppressor cells in tumor immunotherapy: Current, future and beyond

Myeloid-derived suppressor cells (MDSCs) are one of the major negative regulators in tumor microenvironment (TME) due to their potent immunosuppressive capacity. MDSCs are the products of myeloid progenitor abnormal differentiation in bone marrow, which inhibits the immune response mediated by T cells, natural killer cells and dendritic cells; promotes the generation of regulatory T cells and tumor-associated macrophages; drives the immune escape; and finally leads to tumor progression and metastasis. In this review, we highlight key features of MDSCs biology in TME that are being explored as potential targets for tumor immunotherapy. We discuss the therapies and approaches that aim to reprogram TME from immunosuppressive to immunostimulatory circumstance, which prevents MDSC immunosuppression activity; promotes MDSC differentiation; and impacts MDSC recruitment and abundance in tumor site. We also summarize current advances in the identification of rational combinatorial strategies to improve clinical efficacy and outcomes of cancer patients, via deeply understanding and pursuing the mechanisms and characterization of MDSCs generation and suppression in TME.