Abstract 360: Changes in adipose tissue microenvironment occurs early in murine models of pancreatic cancer cachexia
Authors: Jean Sephora , Counts Brittany R. , Gowan Anne E. , Philleo Samuel A. , Cao Sha , Koniaris Leonidas , Zimmers Teresa A. 
Published: April 2023

Cachexia is the unintentional loss of skeletal muscle and adipose tissue. Over 80% of patients with pancreatic adenocarcinoma cancer (PDAC) suffer from cachexia, resulting in reduced survival and quality of life. The magnitude of adipose loss is often greater than muscle loss in patients and animal models. Our prior work in a mouse model of orthotopic PDAC cachexia revealed alterations of multiple pathways in adipose, predominantly inflammation, cytokine signaling, and metabolism. Deconvolution analysis predicts immune cell infiltration and activation. Inflammation-stimulated lipolysis results in fat pad wasting, while the resulting myosteatosis promotes skeletal muscle catabolism. Given this essential role for fat loss in the pathophysiology of cancer cachexia, we aimed to characterize the adipose tissue microenvironment in early and late PDAC cachexia.

Methods: Male C57BL/6J (N=30) mice underwent orthotopic injection of KPC32098 pancreatic cancer cells derived from the LSL-KrasG12D:LSL-Trp53R172H:Pdx1-Cre mouse model or sham surgery. Body composition was determined by serial EchoMRI. Tissues were harvested every three days starting on day 6 after injection until euthanasia on day 18. Bulk RNA sequencing of the entire epididymal fat pad was performed. Single nucleus RNA sequencing of pooled sham (n=4) and pooled day 12 KPC (n=4) epididymal WAT nuclei was performed to identify changes in the adipose tissue microenvironment during cachexia development.

Results: Tumors were palpable on day 9 and increased in size from day 12 (0.612 ± 0.092g) to day 18 (1.79 ± 0.309g, P&lt;0.05). Total body fat loss was evident as early as day 9 (P &lt; 0.001), although epididymal and inguinal white adipose tissues (WAT) were consistently reduced only at days 15 (P=0 and 18. Intrascapular brown adipose tissue (BAT) was reduced by day 18. Histology of skin biopsies showed subcutaneous adipose was reduced by day 12 and absent by day 18, with no difference in epidermis, dermis, or muscle layer thickness. Bulk RNAseq of epididymal WAT in late PDAC cachexia suggested de-differentiation but not browning, including reduced expression of pro-WAT genes Sfrp5, Slc2a4, and Fasn as well as increased expression of the anti-WAT marker Vdr. PPARg targets and other pro-BAT markers trended lower in expression. Early analysis of the snRNAseq data revealed cells positive for Krt18 and Pdx1 in KPC but not sham samples, suggesting that tumor cells are present in the epididymal WAT.

Conclusions: Loss of percentage body fat precedes detectable wasting of individual fat pads in this model of PDAC cachexia. Subcutaneous adipose wasting contributes to this generalized loss of adiposity. Gene expression in late cachexia in orthotopic PDAC suggests de-differentiation but not browning of WAT. Visceral WAT represents a site of tumor micrometastasis, whether as an artifact of the experimental system or as a genuine pathophysiological mechanism.

Citation Format: Sephora Jean, Brittany R. Counts, Anne E. Gowan, Samuel A. Philleo, Sha Cao, Leonidas Koniaris, Teresa A. Zimmers. Changes in adipose tissue microenvironment occurs early in murine models of pancreatic cancer cachexia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 360.