Programmed Cell Death 6 Interacting Protein (PDCD6IP) in Plasma-Derived Exosomes: A Potential Prognostic Biomarker of Melanoma Progression
Abstract
Although much progress has been made in treatment of melanoma, including treatment with immunotherapy, many patients develop drug resistance and fail to respond to the therapy they are receiving. The absence of biomarkers to guide the selection and administration of melanoma therapy is a major barrier which continues to impede progress and negatively affects melanoma-related morbidity and mortality. The development of biomarkers that predict prognosis or response to therapy is an urgent and unmet need. Emerging evidence indicates that exosomes, a subset of extracellular vesicles, are used by melanoma cells to communicate with other cells in the tumor microenvironment (TME) and have attributes that qualify them as promising melanoma biomarkers. This research project investigates the role melanoma cell derived exosomes, called MTEX, play in modifying the TME, promoting melanoma progression and predicting response to therapy. The project is responsive to the Fiscal Year 2021 Melanoma Research Program Challenge to identify how the TME impacts tumor growth, progression and response to therapy. Exosomes are small, virus-size vesicles produced by tumors in great abundance. Exosomes circulate freely, distributing molecular messages from tumor cells to non-malignant cells in the TME and in all other body parts. Melanoma cells use MTEX to communicate with and alter functions of other cells in the TME. The molecular content of MTEX resembles that of melanoma producer cells and, thus, MTEX can serve as surrogates of the tumor in the patients’ plasma (as a liquid tumor biopsy). Using the exosome capturing method we developed, MTEX were separated from non-malignant exosomes (NMTEX) in plasma of melanoma patients previously treated with surgery and various oncological therapies. We then subjected isolated MTEX to mass spectrometry and discovered a small group (n=5) of highly overexpressed proteins that correctly subdivided melanoma patients (n=15) into two groups: those with progressive disease (PD) and those with no evidence of disease (NED). Among the proteins selectively overexpressed in MTEX, ALIX had the greatest discriminating power. Therefore, we focused on ALIX-positive MTEX as a potential biomarker of melanoma progression after oncological therapy. This provocative finding that ALIX overexpression in MTEX was a marker of post-therapy disease progression provided a rationale for the current project in which we will: (1) Corroborate our preliminary data by studying ALIX levels in MTEX isolated from banked plasma of 50 melanoma patients and also evaluate ALIX expression levels in banked melanoma tissue biopsies. To enable testing large numbers of samples, we will utilize a mass spectrometry method which targets only the selected proteins previously found to be differentially expressed in MTEX of PD and NED patients. (2) Perform co-incubations of various immune cells or cultured melanoma cells with MTEX deficient in ALIX or MTEX overexpressing ALIX (such MTEX will be generated by genetic or viral modifications of melanoma cell lines which produce MTEX) and measuring functions, such as cell proliferation or death, of the recipient cells that have taken up MTEX. This will provide mechanistic insights into the role of upregulated ALIX, which is a multifunctional protein, in immune dysregulation in the TME and in tumor growth. As both immune suppression and tumor growth underlie melanoma progression, our results might explain the ALIX role as a potential prognostic biomarker in melanoma. (3) Evaluate the significance of ALIX overexpression in MTEX as a biomarker of prognosis and response to immunotherapy in serially collected pre- and post-therapy plasma specimens of patients with melanoma who were treated in a clinical phase 1 trial. Serial monitoring of ALIX-positive MTEX will be correlated to clinical and outcome data and is expected to serve as a confirmation of the value of MTEX as a potential biomarke
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 28, 2022
- Source ID
- W81XWH2210487
Entities
People
- Theresa Nimick Whiteside
Organizations
- United States Army
- University of Pittsburgh