Podium Presentation in Room 4 on Thursday at 11:20 (Chair: David Muddiman)
Authors: Mary King (1), Robert Yuan (2), Jeremy Chen (2), Isabel Sariol (1), Shirley Li (1), Oscar Ekpenyong (2), Janica C. Wong (2), Jennifer H. Yearley (2), Luis Zúñiga (2), Maribel Beaumont (2)*, Jin-Hwan Han (2)*, and Livia S. Eberlin (1)*
While anti-PD1 treatment has emerged as a transformative therapeutic strategy for cancer patients through inhibition of immune system checkpoint PD-1, only a subset of patients benefits from anti-PD1 therapy. Here, we employ desorption electrospray ionization mass spectrometry imaging (DESI-MSI) to investigate metabolic markers of anti-PD1 treatment response in three syngeneic tumor models, with the expectation of guiding drug administration and patient selection and stratification.
Tumor samples (n=95) from three syngeneic tumor models (MC38, LL/2, and MB49) were prospectively collected from MRL at the baseline and from mice treated with anti-PD-1 or isotype control at days 4, 8, and 15 post-treatment. Samples were sectioned at 5 µm thickness and stored at -80°C until analysis. Tissue sections were analyzed using a Prosolia DESI-MSI platform fitted to a Q-Exactive HF mass spectrometer in negative ion mode at 150 µm spatial resolution. Tissues were H&E stained and evaluated by a pathologist. Data corresponding to tumor cells were extracted and analyzed using significance analysis of microarrays (SAM) (FDR ≤ 5%) to identify treatment markers for each model. Immunofluorescence imaging was performed to identify markers of T cell infiltration on serial tissue sections.
DESI-MSI was used to analyze mouse tumor samples from three syngeneic models sampled at the baseline, and days 4, 8, and 15 of anti-PD1 treatment. The mass spectra obtained presented a rich array of small metabolites, fatty acids, and a diversity of glycerophospholipids. To identify ions with statistically significantly different abundances for each cell line at Day 15, we employed SAM. For the MC38 tumor model of high treatment response, we observed a higher degree of polyunsaturated fatty acid chains of lipids in treated compared to isotype tumor tissue at Day 15. We then plotted the change in average relative abundance of the selected lipid features over time, observing an increase in the abundance of polyunsaturated lipids and a decrease in more saturated lipids in MC38 treated tumor. Preliminary data from immunohistochemical experiments revealed colocalization of T cell infiltration with polyunsaturated lipids. In the LL/2 model of minimal treatment response, we observed that cardiolipin species, a vital component of mitochondrial membranes, were more highly expressed in isotype compared to treated tumors.
Analysis of three syngeneic tumor models with DESI-MSI revealed molecular markers of treatment response in preclinical models of anti-PD-1 therapy.
|Grants||yes||Merck Research Laboratories|
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