Cancer-induced cachexia is a hypermetabolic condition characterized by the unintentional wasting of muscle and adipose tissue, affecting over 80% of patients with pancreatic ductal adenocarcinoma (PDAC). Muscle wasting during cachexia is due to increased skeletal muscle protein degradation via ubiquitin-proteasome and autophagy-lysosome pathways. Autophagy-lysosome degradation requires delivery of cargo to the lysosome for destruction and recycling. Macroautophagy is the most prevalent component of autophagy, encompassing bulk and selective autophagy, and it requires the de novo synthesis of an autophagosome. Bulk autophagy randomly engulfs portions of the cytoplasm. Selective autophagy is mediated through selective autophagy receptors (SAR), which bind and couple cargo to the autophagosome via the general autophagy ligands LC3B and GABARAP. While an increase in the general autophagy machinery is well described in cachectic muscle, much less is known about how complexes and organelles are selectively targeted for degradation. Methods: Here, 12-week-old male C57BL/6J mice were orthotopically implanted with 1x105 KPC cells; controls underwent sham surgery. Half of the tumor-bearing mice were treated with 120 mg/kg gemcitabine and 10 mg/kg nab-paclitaxel (GemNP) at 4 and 10 days. For endpoint analysis, mice were euthanized at 14 days when KPC mice had significant body weight, muscle mass and muscle protein loss compared to SHAM controls. In our in vitro model of PDAC cachexia, KPC-conditioned media (CM) induces C2C12 myotube wasting; thus, myotubes were treated with 50% KPC-CM or control for 48hrs. Results: GemNP reduced end tumor mass by nearly 25% and prevented body weight and muscle loss. mRNAseq of gastrocnemius muscle demonstrated induction of ribosomal component gene expression, while deep proteomics revealed reduction of 30 ribosomal component proteins in KPC mice, consistent with ongoing destruction of ribosomes. Gene expression of general autophagy ligands, LC3B (2.9-fold) and GABARAP (1.6-fold), were increased in KPC mice. Gene expression for SARs associated with ribophagy (NUFIP1, 2.6-fold) and reticulophagy (Fam134b, 11.3-fold) were increased in KPC. FAM134b protein (1.8-fold) was also increased in KPC mice. SARs for lipophagy (PNPLA2, 3.2- and PNPLA8, 1.8-fold) and mitophagy (BNIP3, 4.5-fold) were induced in KPC versus SHAM, while SARs for glycophagy and ferritinophagy were similar. SQSTM1 (3.9-fold) and NBR1 (1.9-fold), general SARs for multiple organelles including aggrephagy, lysophagy, proteaphagy and pexophagy, were increased in KPC. This activation of SARs was due to tumor-induced wasting and not chemotherapy as SAR gene expression in KPC-GemNP mice was similar to SHAM controls. Finally, we also observe markers of SAR-mediated autophagy in our in vitro model of PDAC cachexia. Conclusion: These data indicate that muscle wasting in PDAC cachexia is through activation of selective autophagy of ribosomes, mitochondria, lipid droplets, endoplasmic reticulum, protein aggregates, lysosomes, peroxisomes, and proteasomes. Citation Format: Brittany R. Counts, Ashok Narasimhan, Tara S. Umberger, Emma H. Doud, Amber L. Mosley, Teresa A. Zimmers. Skeletal Muscle Selective Autophagy Receptors are induced PDAC Cachexia [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr A062.

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<0.05). Total body fat loss was evident as early as day 9 (P < 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.