Cancer cells form three dimensional (3D) multicellular aggregates (or
spheroids) under non-adherent culture conditions. In ovarian cancer (OC),
spheroids serve as a vehicle for cancer cell dissemination in the peritoneal
cavity, protecting cells from environmental stress-induced anoikis. To identify
new targetable molecules in OC spheroids, we investigated gene expression
profiles and networks upregulated in three dimensional (3D) versus traditional
monolayer culture conditions. We identified ALDH1A1, a cancer
stem cell marker as being overexpressed in OC spheroids and directly connected
to key elements of the β-catenin pathway. B-catenin function and
ALDH1A1 expression were increased in OC spheroids vs.
monolayers and in successive spheroid generations, suggesting that 3D aggregates
are enriched in cells with stem cell characteristics. B-catenin knockdown
decreased ALDH1A1 expression levels and β-catenin
coimmunoprecipitated with the ALDH1A1 promoter, suggesting that
ALDH1A1 is a direct β-catenin target. Both siRNA
mediated β-catenin knockdown and A37, a novel ALDH1A1 small molecule
enzymatic inhibitor described here for the first time, disrupted OC spheroid
formation and cell viability (p<0.001). B-catenin knockdown blocked tumor
growth and peritoneal metastasis in an OC xenograft model. These data strongly
support the role of β-catenin regulated ALDH1A1 in the maintenance of OC
spheroids and propose new ALDH1A1 inhibitors targeting this cell population.
SUMMARY
Mitochondria undergo fission and fusion to maintain homeostasis, and tumors exhibit the dysregulation of mitochondrial dynamics. We recently demonstrated that ectopic HRas
G12V
promotes mitochondrial fragmentation and tumor growth through Erk phosphorylation of the mitochondrial fission GTPase Dynamin-related protein 1 (Drp1). However, the role of Drp1 in the setting of endogenous oncogenic KRas remains unknown. Here, we show that Drp1 is required for KRas-driven anchorage-independent growth in fibroblasts and patient-derived pancreatic cancer cell lines, and it promotes glycolytic flux, in part through the regulation of hexokinase 2 (HK2). Furthermore, Drp1 deletion imparts a significant survival advantage in a model of KRas-driven pancreatic cancer, and tumors exhibit a strong selective pressure against complete Drp1 deletion. Rare tumors that arise in the absence of Drp1 have restored glycolysis but exhibit defective mitochondrial metabolism. This work demonstrates that Drp1 plays dual roles in KRas-driven tumor growth: supporting both glycolysis and mitochondrial function through independent mechanisms.
Patients with pancreatic ductal adenocarcinoma (PDAC) who undergo surgical resection and adjuvant chemotherapy have an expected survival of only 2 years due to disease recurrence, frequently in the liver. We investigated the role of liver macrophages in progression of PDAC micrometastases to identify adjuvant treatment strategies that could prolong survival. A murine splenic injection model of hepatic micrometastatic PDAC was used with five patient-derived PDAC tumors. The impact of liver macrophages on tumor growth was assessed by (i) depleting mouse macrophages in nude mice with liposomal clodronate injection, and (ii) injecting tumor cells into nude versus NOD--gamma mice. Immunohistochemistry and flow cytometry were used to measure CD47 ("don't eat me signal") expression on tumor cells and characterize macrophages in the tumor microenvironment. engulfment assays and mouse experiments were performed with CD47-blocking antibodies to assess macrophage engulfment of tumor cells, progression of micrometastases in the liver and mouse survival. clodronate depletion experiments and NOD--gamma mouse experiments demonstrated that liver macrophages suppress the progression of PDAC micrometastases. Five patient-derived PDAC cell lines expressed variable levels of CD47. In engulfment assays, CD47-blocking antibodies increased the efficiency of PDAC cell clearance by macrophages in a manner which correlated with CD47 receptor surface density. Treatment of mice with CD47-blocking antibodies resulted in increased time-to-progression of metastatic tumors and prolonged survival. These findings suggest that following surgical resection of PDAC, adjuvant immunotherapy with anti-CD47 antibody could lead to substantially improved outcomes for patients. .
Background: A "headless" Myo10 that lacks a motor domain has been identified in the nervous system, but its functions are unknown. Results: Headless Myo10 inhibits axon outgrowth and antagonizes the filopodia-inducing activity of full-length Myo10. Conclusion: Full-length Myo10 is required for axon outgrowth, and headless Myo10 can inhibit full-length Myo10. Significance: This study establishes opposing roles for headless and full-length Myo10 in axon outgrowth.
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