Epigenetic Tumor Suppressor KMT2D Shapes the Immune Landscape in Pancreatic Cancer 2335260
TL;DR
KMT2D plays a pivotal role in orchestrating both tumor-intrinsic and microenvironmental processes that drive pancreatic cancer progression, and understanding how KMT2D loss reprograms the immune landscape may uncover novel immunomodulatory therapeutic targets for pancreatic cancer.
Abstract
KMT2D (known as Mll4 in mice) is a histone methyltransferase and a critical epigenetic regulator frequently mutated across a range of cancers. TCGA data indicate alterations in KMT2D, including mutations and changes in expression, in approximately 11% of pancreatic cancer patients. Our previous research showed that KMT2D loss in human pancreatic cancer cells induces epithelial-to-mesenchymal transition (EMT), promoting aggressive disease progression. We hypothesized that KMT2D loss not only drives intrinsic tumor changes but also remodels the immune microenvironment. We performed bulk RNA sequencing on Mll4 knockdown mouse pancreatic cancer cells (KPC7940) and proteomic profiling of their conditioned media to identify changes in secreted proteins. Pathway analysis focused on TNF-alpha/NF-kB, IL-6/JAK/STAT3, and IL-2/STAT5 signaling. A pancreas-specific Mll4 knockout model (KPCM: KrasG12D/+; Trp53R172H/+; Ptf1a-Cre; Mll4SETflox/flox) was generated to assess tumor progression in vivo. Tumor proliferation was evaluated by Ki-67 immunohistochemistry. Single-cell RNA sequencing was used to characterize the immune microenvironment in KPC and KPCM tumors. KPCM mice developed pancreatic cancer by 3 weeks compared to 16—20 weeks in KPC controls, with median survival of 24 vs 126.5 days. Ki-67 staining confirmed higher proliferation in KPCM tumors. Bulk RNA-seq and proteomic analysis revealed altered expression of secreted proteins enriched in inflammatory and immunomodulatory pathways. Single-cell RNA sequencing showed increased myeloid populations and NK/T cells expressing immunosuppressive markers, including CTLA4, CD274, and PDCD1, in KPCM tumors. KMT2D plays a pivotal role in orchestrating both tumor-intrinsic and microenvironmental processes that drive pancreatic cancer progression. Understanding how KMT2D loss reprograms the immune landscape may uncover novel immunomodulatory therapeutic targets for pancreatic cancer. n/a Tumor Immunology: Cellular Responses and Tumor Microevironment (TIME)