Nuclear GRP78 Promotes Metabolic Reprogramming and Therapeutic Resistance in Pancreatic Ductal Adenocarcinoma

摘要

Purpose: Stromal fibrosis limits nutritional supply and disarrays metabolism in pancreatic cancer (PDA, pancreatic ductal adenocarcinoma). Understanding of the molecular basis underlying metabolic cues would improve PDA management. The current study determined the interaction between glucose-regulated proteins 78 (GRP78) and hypoxia-inducible factor 1 alpha (HIF-1 alpha) and its mechanistic roles underlying PDA response to oxygen and glucose restrains.Experimental Design: Gene expression and its association with clinicopathologic characteristics of patients with PDA and mouse models were analyzed using IHC. Protein expression and their regulation were measured by Western blot and immunoprecipitation analyses. Protein interactions were determined using gain- and loss-of-function assays and molecular methods, including chromatin immunoprecipitation, co-immunoprecipitation, and dual luciferase reporter.Results: There was concomitant overexpression of both GRP78 and HIF-1 alpha in human and mouse PDA tissues and cells. Glucose deprivation increased the expression of GRP78 and HIF-1 alpha, particularly colocalization in nucleus. Induction of HIF-1 alpha expression by glucose deprivation in PDA cells depended on the expression of and its own interaction with GRP78. Mechanistically, increased expression of both HIF-1 alpha and LDHA under glucose deprivation was caused by the direct binding of GRP78 and HIF-1 alpha protein complexes to the promoters of HIF-1 alpha and LDHA genes and transactivation of their transcriptional activity.Conclusions: Protein complex of GRP78 and HIF-1 alpha directly binds to HIF-1 alpha own promoter and LDHA promoter, enhances the transcription of both HIF-1 alpha and LDHA, whereas glucose deprivation increases GRP78 expression and further enhances HIF-1 alpha and LDHA transcription. Therefore, crosstalk and integration of hypoxia- and hypoglycemia-responsive signaling critically impact PDA metabolic reprogramming and therapeutic resistance.

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