Pancreatic cancers are notoriously aggressive and drug-resistant, and surgical resection is complicated by widespread intraperitoneal dissemination and ascites. One component of malignant ascites is lysophosphatidic acid (LPA), a bioactive lipid that promotes multiple aspects of tumor progression. Here, I report that expression of the cancer stem cell marker αvβ3 integrin is necessary and sufficient for the production of LPA. In turn, LPA was shown to induce the expression of stem genes OCT4 and NANOG and promote anchorage-independent growth. Upon interrogating the LPA metabolic pathway, I found that expression of αvβ3 integrin is necessary and sufficient to promote the expression of cytoplasmic phospholipase A2 (cPLA2), an important enzyme in the production of LPA. Furthermore, αvβ3 integrin forms a physical complex with cPLA2 to stabilize and stimulate its activity. Subsequently, KRAS mutant pancreatic cancer cells utilize LPA to overcome the effects of cellular stress, including cancer therapy. A variety of stress, including nutrient deprivation, oxidative stress, and treatment with standard-of-care chemotherapies, sensitizes cells to LPA-induced migration as well as KRAS-driven advantages such as macropinocytosis in response to nutrient stress and ROS elimination in response to oxidative stress. In order to cope with these stresses, cancer cells selectively upregulate the expression of LPA Receptor 4 (LPAR4). I illustrate that this receptor is necessary and sufficient for adaptation to stress in vitro and tumor progression in vivo. I showed that LPAR4 is necessary and sufficient to activate the Gαs/cAMP/PKA signaling pathway and that this pathway is required for LPA-mediated protection from stress. This is accomplished through activation of Vasodilator Stimulated Phosphoprotein (VASP), an enzyme involved in actin polymerization. Ultimately, I found that VASP is necessary for stress-mediated and LPAR4-mediate migration and macropinocytosis. My work highlights how stress changes the repertoire of LPA receptors, leading to dependence on LPAR4 by virtue of its stress mitigating functions, such as macropinocytosis and ROS elimination. Furthermore, my findings illustrate that αvβ3 integrin expressing cancer stem-like cells can secrete the bioactive lipid LPA through cPLA2 upregulation. Subsequently, cellular stress drives a more aggressive cancer phenotype by priming pancreatic cells to be highly responsive to LPA.

Glioblastoma ranks among the most aggressive and lethal of all human cancers. Self-renewing, highly tumorigenic glioblastoma stem cells (GSCs) contribute to therapeutic resistance and maintain cellular heterogeneity. Here, we interrogated superenhancer landscapes of primary glioblastoma specimens and patient-derived GSCs, revealing a kelch domain-containing gene (KLHDC8A) with a previously unknown function as an epigenetically-driven oncogene. Targeting KLHDC8A decreased GSC proliferation and self-renewal, induced apoptosis, and impaired in vivo tumor growth. Transcription factor control circuitry analyses revealed that the master transcriptional regulator SOX2 stimulated KLHDC8A expression. Mechanistically, KLHDC8A bound Chaperonin-Containing TCP1 (CCT) to promote assembly of primary cilia to activate Hedgehog signaling. KLHDC8A expression correlated with Aurora B/C Kinase inhibitor activity, which induced primary cilia and Hedgehog signaling. Combinatorial targeting of Aurora B/C Kinase and Hedgehog displayed augmented benefit against GSC proliferation. Collectively, superenhancer-based discovery revealed KLHDC8A as a novel molecular target of cancer stem cells that promotes ciliogenesis to activate the Hedgehog pathway, offering insights into therapeutic vulnerabilities for glioblastoma treatment.

Pancreatic cancer is notoriously known for being aggressive and resistant to chemotherapy. It has one of the highest rates of recurrence among all cancers and a poor survival rate even after treatment. The tumor microenvironment in pancreatic cancer, also known as a “niche”, is characterized by the deposition of a dense extracellular matrix (ECM). To establish a tumor at a primary or metastatic site, tumor-initiating cells (TICs) must adapt and survive in a highly hostile environment characterized by hypoxia, nutrient deprivation, and oxidative stress, together known as isolation stress. TICs accomplish this by gaining stem-like features which ultimately lead to a stress-tolerant phenotype. Pancreatic cancer cells upregulate a receptor called lysophosphatidic acid receptor-4 (LPAR4) in response to isolation stress. LPAR4 expression is necessary and sufficient to establish a tumor-initiating niche, which plays an important role in cancer progression. A characteristic of this niche is the enrichment of the ECM component fibronectin (FN), which interacts with cells through cell-surface integrin receptors. These interactions activate various signaling molecules such as the transcriptional regulator Yes-associated protein (YAP), consequently driving cancer stemness. In this study, I investigate the adaptive gain of a stress-tolerant phenotype in LPAR4- cells mediated by a FN-enriched ECM deposited by LPAR4+ cells. I report that the ectopic expression of LPAR4 in pancreatic cancer cells is sufficient to induce a stress-tolerant phenotype and YAP activation, through the elevated expression of FN. Knockout of FN in LPAR4+ cells can hamper YAP activation, emphasizing the crucial role of FN in YAP signaling. Furthermore, the ECM deposited by LPAR4+ cells is sufficient to confer the stress-tolerant phenotype to neighboring LPAR4- cells through paracrine signaling by a fibronectin-dependent pathway, leading to integrin-mediated activation of YAP and expression of YAP targets CTGF and CYR61. A pure FN-matrix is sufficient to induce YAP activation in LPAR4- cells, indicating that FN is the key ECM component that interacts with cell surface integrin receptors to drive cancer stemness in response to isolation stress. Together, all these factors help tumor-initiating cells to survive isolation stress, resist chemotherapy, and form aggressive tumors, leading to pancreatic cancer progression.

Pancreatic cancer is characterized by a dense fibrotic stroma, consisting of cancer-associated fibroblasts (CAFs), immune cells, and extracellular matrix (ECM) that promote tumor growth and treatment resistance. CAFs secrete and organize on their surface ECM proteins, including fibronectin (FN) which coordinates the assembly of collagen fibrils that promote matrix stiffness. Since CAFs are a major contributor to fibrosis and the progression of pancreatic cancer, novel approaches to target their function could have a significant impact on patient outcome. This research demonstrates that the ability of pancreatic cancer cells to initiate tumors in mice is greatly enhanced by co-injection of CAFs. Targeting FN via FN-binding integrins α5β1 and αvβ3 that are highly expressed on CAFs disrupts CAF-induced fibrosis, decreases tumor stiffness, and prevents the initiation of pancreas tumors in mice. These results highlight the therapeutic potential of targeting fibronectin-binding integrins, α5β1 and αvβ3, on CAFs to disrupt the fibrotic stroma in pancreatic cancer.