SUMMARY/ABSTRACT Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers with limited therapeutic options. About 95% PDAC patients harbor oncogenic mutant KRAS (KRAS*) that promotes pancreatic carcinogenesis and is required for PDAC maintenance. Given that KRAS* can be druggable now, therapy resistance occurs in several pre-clinical models and clinical trials, suggesting that therapy combination is required to achieve durable disease control. Targeting KRAS* results in enrichment of tumor associated macrophages (TAMs) in pancreatic, colon and lung cancer models, offering opportunities for chimeric antigen receptor (CAR) macrophage (Mφ) therapy and for Mφ-mediated cancer-specific delivery of pro-inflammatory cytokines. However, transplanted Mφs were prone to accumulate in liver, lung, and spleen despite that most of the remaining Mφs were localized in tumors, rising safety concerns that might be addressed by conditional gene expression systems. The hypothesis is that tumor-conditionally expressed cytokine armored CAR Mφs (ca-CAR-Ms) may synergize with KRAS* inhibitors (KRASi) to effectively suppress primary tumor growth, metastasis, and tumor recurrence and to prolong survival in PDAC spontaneous metastasis mouse models. A successful outcome of proposed study will generate the first ca-CAR-M therapy for PDAC treatment, pave the way for clinical trials in KRAS* PDAC patients and provide applicable methods to develop ca-CAR-Ms for other Mφ-enriched cancers. Aim 1. Optimize cell culture and engineering platforms for adoptive macrophage therapy. Primary Mφs are non-proliferative in vitro, and accumulation of donor Mφs in healthy organs is a latent safety risk. Aim 1a will enable in vitro expansion of Mφs by genetic or chemical screening of Mφ self-renewal regulators. Aim 1b will limit off-tumor activity of donor Mφs by employing dual oxygen-sensing switch and identifying TAM-specific genes versus tissue-resident Mφs, whose promoter/enhancers will be used for tumor-specific gene expression. Aim 2. Design CAR Mφs to target PDAC. The comprehensive CAR optimization for effective antigen-specific activation of phagocytosis and cytotoxicity in Mφs is lacking. Aim 2a will design and optimize constituent protein domains of CAR to direct Mφ activities against PDAC. Aim 2b will determine the tumoricidal effect of CAR-Ms as an adjuvant therapy of KRASi in PDAC models. Aim 2c will dissect mechanisms how CAR activation reprograms Mφ transcription, secretion, and pathway transduction to elicit tumoricidal effect. Aim 3. Engineer conditionally armored Mφs to trigger tumoricidal immunity. Mφs are tumor-homing, so delivery of pro-inflammatory cytokines by Mφs may reduce systemic toxicity while elicit strong anti-tumor immune response. Aim 3a will develop safe and effective cytokine armored Mφ therapy by cytokine screening and employing conditional transgene expression system. Aim 3b will assess tumoricidal activity of Mφs engineered by the optimal CAR construct, the top cytokine candidate or both as an adjuvant therapy of KRASi in various PDAC models. Aim 3c will delineate the role of cytokine armored Mφs in the tumor microenvironment remodeling by single cell RNA sequencing and immunophenotyping.

NARRATIVE Patients with advanced pancreatic ductal adenocarcinoma desperately need novel and effective therapeutics. Macrophage allotransplantation seems permissive, making them a safe choice as a “third-party, off-the-shelf” cell therapy option. The proposed research will not only provide a proof-of-concept regarding the combination therapy of KRAS inhibitors and macrophages genetically engineered with chimeric antigen receptors and pro- inflammatory cytokines, but will also enhance the understanding of macrophage self-renewal, plasticity, signaling transduction and function execution.