HPLC Measures EV Immune Activity in Melanoma

Extracellular vesicles (EVs) are tiny particles released by melanoma cells which carry specific proteins on their surface that help convert one chemical into another, ultimately producing a substance that dials down the immune system's ability to fight the cancer. Researchers affiliated with a joint study conducted by UPMC Hillman Cancer Center and the University of Pittsburgh (both in Pittsburgh, Pennsylvania) suspected that these tumor-derived particles were the primary drivers of this immune-suppressing process in cancer patients' blood. To test that idea, they collected blood samples from melanoma patients (some whose cancer was undetectable at the time, and some with active, spreading disease). They then separated the tumor-derived particles from those produced by healthy cells and measured the immune-suppressing activity of each group, as well as of all the particles combined, using high-performance liquid chromatography (HPLC) with fluorescence detection. A paper based on this work was published in the journal OncoImmunology.¹

Why Doesn't Immunotherapy Work for All Cancer Patients?

Immunotherapy drugs that work by releasing the brakes on the immune system have produced remarkable results across many cancer types, but they don't work for everyone, and for a significant number of patients, any initial benefit does not last.^2-4 The reasons for this are complex and not yet fully understood, but one key factor may be the cancer's own ability to shield itself from the immune system.^5,6 Tumors can actively reshape their surrounding environment in ways that either push immune cells out entirely or leave behind only worn-out, ineffective ones that are no longer capable of mounting a meaningful attack.^5,8

What Did the Study Find, and What Could These Findings Mean for the Future of Cancer Monitoring and Treatment?

The researchers admitted surprise to find that the tiny particles not directly tied to the tumor showed higher levels of immune-suppressing activity than those coming from the tumor itself. However, this difference was not linked to how advanced a patient's disease was; what did track with disease progression was the overall level of immune-suppressing activity across all the particles combined (patients whose cancer had spread showed significantly higher levels compared to those whose disease was not currently detectable). This suggests that in cancer patients, both tumor-derived and non-tumor-derived particles in the blood contribute to the process by which the cancer suppresses the immune system. Looking at all the particles together, rather than just those coming from the tumor, may therefore give a more complete and clinically useful picture of how much immune suppression a given patient is experiencing.¹

While this study had some limitations (including a relatively small and varied group of patients), the testing method the researchers developed offers a promising new way to monitor cancer using a simple blood sample. With just one milliliter of plasma, it is possible to build a personalized picture of how a patient's immune system is being affected by their cancer, and to track how that picture changes over time. This is made possible in part because cancer patients tend to have significantly higher numbers of the tiny particles being measured circulating in their blood.¹

The researchers are currently confirming these findings in a larger clinical trial, with further validation efforts also in progress. Ultimately, this approach could prove valuable not only for predicting how a melanoma patient's disease might progress, but also for anticipating how well they might respond to immunotherapy. The potential applications may also extend well beyond melanoma to other diseases.¹

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References

1. Najjar, Y. G.; Hong, C. S.; Menshikova, E. V. et al. Purinergic Activity of Circulating Extracellular Vesicles Associates with Disease Progression in Melanoma. Oncoimmunology 2026, 15 (1), 2688603.DOI: 10.1080/2162402X.2026.2688603
2. Campbell, K. M.; Amouzgar, M.; Pfeiffer, S. M. et al. Prior Anti-CTLA-4 Therapy Impacts Molecular Characteristics Associated with Anti-PD-1 Response in Advanced Melanoma. Cancer Cell 2023, 41 (4), 791-806.e4. DOI: 10.1016/j.ccell.2023.03.010
3. Huang, A. C.;Zappasodi, R. A Decade of Checkpoint Blockade Immunotherapy in Melanoma: Understanding the Molecular Basis for Immune Sensitivity and Resistance. Nat Immunol. 2022, 23 (5), 660-670. DOI: 10.1038/s41590-022-01141-1
4. Otto, G. Diverse Routes to Melanoma Metastasis and ICI Resistance. Nat Cancer 2023, 4 (12), 1643. DOI: 10.1038/s43018-023-00679-9
5. Cerezo-Wallis, D.; Contreras-Alcalde, M.; Troulé, K. et al. Midkine Rewires the Melanoma Microenvironment Toward a Tolerogenic and Immune-Resistant State. Nat Med. 2020, 26 (12), 1865-1877. DOI: 10.1038/s41591-020-1073-3
6. Bu, M. T.; Chandrasekhar, P.; Ding, L. et al. The Roles of TGF-β and VEGF Pathways in the Suppression of Antitumor Immunity in Melanoma and Other Solid Tumors. Pharmacol Ther. 2022, 240, 108211. DOI: 10.1016/j.pharmthera.2022.108211
7. Fujiwara, Y.; Kato, S.; Nesline, M. K. et al. Indoleamine 2,3-dioxygenase (IDO) Inhibitors and Cancer Immunotherapy. Cancer Treat Rev. 2022, 110, 102461. DOI: 10.1016/j.ctrv.2022.102461
8. Wu, B.; Zhang, B.; Li, B. et al. Cold and Hot Tumors: From Molecular Mechanisms to Targeted Therapy. Signal Transduct Target Ther. 2024, 9 (1), 274. DOI: 10.1038/s41392-024-01979-x