Senescent CAFs Mediate Immunosuppression and Drive Breast Cancer Progression

The tumor microenvironment (TME) profoundly influences tumorigenesis, with gene expression in the breast TME capable of predicting clinical outcomes. The TME is complex and includes distinct cancer-associated fibroblast (CAF) subtypes whose contribution to tumorigenesis remains unclear. Here, we identify a subset of myofibroblast CAFs (myCAF) that are senescent (senCAF) in mouse and human breast tumors. Utilizing the MMTV-PyMT;INK-ATTAC (INK) mouse model, we found that senCAF-secreted extracellular matrix specifically limits natural killer (NK) cell cytotoxicity to promote tumor growth. Genetic or pharmacologic senCAF elimination unleashes NK cell killing, restricting tumor growth. Finally, we show that senCAFs are present in HER2+, ER+, and triple-negative breast cancer and in ductal carcinoma in situ (DCIS) where they predict tumor recurrence. Together, these findings demonstrate that senCAFs are potently tumor promoting and raise the possibility that targeting them by senolytic therapy could restrain breast cancer development.

SIGNIFICANCE

senCAFs limit NK cell-mediated killing, thereby contributing to breast cancer progression. Thus, targeting senCAFs could be a clinically viable approach to limit tumor progression.

Abstract 4796: Chemotherapy induced senescence drives peripheral neuropathy

Chemotherapy is a mainstay of cancer therapy. Unfortunately, while chemotherapy can profoundly impact disease free survival, it’s often accompanied with devastating side effects, including peripheral neuropathy. Indeed, 30-40% of patients treated with neurotoxic chemotherapy develop long-term and often debilitating chemotherapy-induced peripheral neuropathy (CIPN). Unfortunately, there are currently no preventative measures for CIPN and while it is transitory in some patients, for others the side effects can persist for months or even years after the cessation of chemotherapy. Recent work suggests that cellular senescence, which is robustly induced by chemotherapy, contributes to CIPN. Senescent cells are typically characterized by increased CDKn2a (i.e., p16) expression, increased SA-β-gal hydrolyzation, and expression of the senescence-associated secretory phenotype (SASP) that can influence multiple cell types in the microenvironment. Through utilization of a mouse model that employs paclitaxel (PTX), we find that PTX robustly induces senescence in the hindpaws and dorsal root ganglia (DRG) of mice that display loss of peripheral axons and decreased response to mechanical stimuli. To address the role of senescence in CIPN, we utilized the INKATTAC mouse that allows for inducible elimination senescent cells. Using this model, we find that the elimination of senescent cells rescues CIPN. Further, the use of senolytics, drugs that kill senescent cells, also rescues CIPN, raising the possibility that we can treat patients with CIPN. To address the mechanism behind CIPN we have carried out single cell RNA-Seq to identify the population of senescent cells senescing in response to chemotherapy. These analyses will allow us to understand the mechanisms that drive CIPN and may lead to new treatments for patients suffering from CIPN.

Citation Format: Taylor Malachowski, Ganesh Raut, Satarupa Mullick Bagchi, Shelia Stewart. Chemotherapy induced senescence drives peripheral neuropathy. [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 4796.

Demonstration of a Common DPhe7 to DNal(2')7 Peptide Ligand Antagonist Switch for Melanocortin-3 and Melanocortin-4 Receptors Identifies the Systematic Mischaracterization of the Pharmacological Properties of Melanocortin Peptides

Melanocortin peptides containing a 3-(2-naphthyl)-d-alanine residue in position 7 (DNal(2')⁷), reported as melanocortin-3 receptor (MC3R) subtype-specific agonists in two separate publications, were found to lack significant MC3R agonist activity. The cell lines used at the University of Arizona for pharmacological characterization of these peptides, consisting of HEK293 cells stably transfected with human melanocortin receptor subtypes MC1R, MC3R, MC4R, or MC5R, were then obtained and characterized by quantitative polymerase chain reaction (PCR). While the MC1R cell line correctly expressed only hMCR1, the three other cell lines were mischaracterized with regard to receptor subtype expression. The demonstration that a 3-(2-naphthyl)-d-alanine residue in position 7, irrespective of the melanocortin peptide template, results primarily in the antagonism of MC3R and MC4R then allowed us to search the published literature for additional errors. The erroneously characterized DNal(2')⁷-containing peptides date back to 2003; thus, our analysis suggests that systematic mischaracterization of the pharmacological properties of melanocortin peptides occurred.

Dengue Virus Infection: A Tale of Viral Exploitations and Host Responses

Dengue is a mosquito-borne viral disease (arboviral) caused by the Dengue virus. It is one of the prominent public health problems in tropical and subtropical regions with no effective vaccines. Every year around 400 million people get infected by the Dengue virus, with a mortality rate of about 20% among the patients with severe dengue. The Dengue virus belongs to the Flaviviridae family, and it is an enveloped virus with positive-sense single-stranded RNA as the genetic material. Studies of the infection cycle of this virus revealed potential host targets important for the virus replication cycle. Here in this review article, we will be discussing different stages of the Dengue virus infection cycle inside mammalian host cells and how host proteins are exploited by the virus in the course of infection as well as how the host counteracts the virus by eliciting different antiviral responses.