As cancer research advances, researchers uncover more mechanisms involved in therapeutic evasion, which allows cancer cells to avoid the effects of treatments. Immunotherapies, which harness the patient’s own immune system to fight cancer cells, have correlated with improved outcomes and survival in numerous different types of cancers. Despite these advances, cancer cell adaptation and evasion remains a major challenge for researchers, decreasing the efficacy of targeted treatments. Researchers continue to seek novel therapies and targets to improve outcomes in cancer patients to combat cancer adaptions, a challenge that functional proteomics has begun to overcome.
Osteopontin (OPN) is a protein that is expressed by multiple tumor cell types and is associated with metastasis and poor survival rates.1 Contrastingly, OPN expression has been recorded in healthy myeloid cells and could contribute to immunosuppression, pointing to OPN as a potential drug target for novel therapies looking to improve cancer patient outcomes as decreasing OPN expression could have therapeutic benefit.1 That being said, previous studies using neutralizing antibodies to block the effects of secreted OPN showed little effect, indicating that intracellular, rather than secreted, OPN may be driving tumor malignancy.2 Therefore, alternative methods of OPN inhibition targeting OPN before it is expressed may be more effective in reducing tumor burden and maintaining anti-tumor immune response. IsoPlexis’ Single-Cell Secretome platform could help researchers elucidate the functional impact of targeted therapies and profile the mechanisms driving OPN infiltration and immune cell activity within myeloid cells.
Targeting OPN in Myeloid Cells Alters Their Function
In a recent paper published in OncoImmunology, researchers knocked down OPN using small interfering RNA (siRNA) designed to inhibit OPN expression.3 In the experiment, the OPN siRNA was targeted separately to cancer cells and myeloid cells using sequences specific to each type of cell. The researchers purified CD11b+ myeloid cells derived from the bone marrow of healthy donors and incubated them with a control non-targeting (NT) siRNA or the targeted siRNA (CPG-OPN siRNA) for 36 hours.
Following purification, Researchers used IsoPlexis’ Single-Cell Secretome platform to assess the cytokine profiles of the CD11b+ myeloid cells. They found that, while cytokine secretion profiles were generally similar, the cells treated with the targeted siRNA had significantly lower levels of granulocyte macrophage colony-stimulating factor (GM-CSF), IL-18, and migratory inhibition factor (MIF). Notably, MIF has previously been identified as being immunosuppressive when secreted by the tumor microenvironment and, in a previous study, MIF inhibition restored anti-tumor immune activity.4 This study demonstrates how IsoPlexis’ Single-Cell Secretome platform can be used to uncover mechanisms of tumor evasion and increase efficacy of cancer therapeutics.
Using Single-Cell Cytokine Analysis to Better Understand Immunotherapies
This study demonstrates how single-cell cytokine analysis can be used to better understand how immune cells respond to therapies. By identifying how myeloid cell function changes in response to OPN knockdown, the authors provide a potential mechanism that can be targeted by future therapies. As single-cell functional phenotyping broadens our understanding of immune cells, researchers can harness these findings to create better treatments and improve cancer outcomes.
- Sangaletti S, Tripodo C, Sandri S, et al. Osteopontin Shapes Immunosuppression in the Metastatic Niche. Cancer Research. 2014;74(17):4706-4719. doi:10.1158/0008-5472.CAN-13-3334
- Wei J, Marisetty A, Schrand B, et al. Osteopontin mediates glioblastoma-associated macrophage infiltration and is a potential therapeutic target. J Clin Invest. 2019;129(1):137-149. doi:10.1172/JCI121266
- Wei J, Song R, Sabbagh A, et al. Cell-directed aptamer therapeutic targeting for cancers including those within the central nervous system. Oncoimmunology. 2022;11(1):2062827. doi:10.1080/2162402X.2022.2062827
- de Azevedo RA, Shoshan E, Whang S, et al. MIF inhibition as a strategy for overcoming resistance to immune checkpoint blockade therapy in melanoma. Oncoimmunology. 2020;9(1):1846915. doi:10.1080/2162402X.2020.1846915