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Fructose-1,6-bisphosphatase loss modulates STAT3-dependent expression of PD-L1 and cancer immunity.

ABSTRACT: Rationale: Abnormal expression of programmed death-1 (PD-1) ligand-1(PD-L1) in cancer cells plays a crucial role in cancer immune evasion and progression. The immune checkpoint molecules PD-1 and PD-L1 have been targeted for cancer treatment with significant benefits for cancer patients. However, the response rate is relatively low in certain types of cancer and the underlying mechanism remains poorly understood. Better understanding of the molecular mechanism of PD-L1 expression regulation in cancer cells is urgently needed to improve the treatment response rate and overall survival of patients. Fructose-1, 6-biphosphatase (FBP1) is a key enzyme in gluconeogenesis and is implicated in human cancer due to its frequent loss in various cancer types. Methods: Expression of FBP1 and PD-L1 was analyzed in various cancer cell lines. Western blot and RT-qPCR were performed to determine whether FBP1 regulates PD-L1 expression. Co-immunoprecipitation and glutathione S-transferase (GST) pulldown assay were employed to define the underlying regulatory mechanisms. Immunohistochemistry was conducted to determine the correlation between FBP1 and PD-L1 expression in a cohort of patients. A cancer syngeneic mouse model was utilized to examine how FBP1 affects tumor immunity. Results: We demonstrated that in a manner independent of its enzymatic activity FBP1 downregulates the expression of PD-L1 in various cell lines of different cancer types including pancreatic and prostate cancer. We further showed that this regulation occurs at the transcriptional level and is mediated by FBP1 inhibition of signal transducer and activator of transcription-3 (STAT3)-dependent PD-L1 transcription. Moreover, FBP1 and PD-L1 protein expression were negatively correlated in pancreatic ductal adenocarcinoma (PDAC) specimens from a cohort of patients. Most importantly, we demonstrated that decreased FBP1 expression promotes tumor growth and resistance to immune checkpoint blockade therapy in mice. Conclusions: Our findings reveal a new tumor suppressor function of FBP1 in inhibiting PD-L1 expression and enhancing cancer immunity. They also suggest that FBP1-deficient human cancers could be therapeutically targeted by PD-1/PD-L1-based immune checkpoint blockade therapy.

SUBMITTER: Wang B

PROVIDER: S-EPMC6956820 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Fructose-1,6-bisphosphatase loss modulates STAT3-dependent expression of PD-L1 and cancer immunity.

Wang Bo B Zhou Yingke Y Zhang Jun J Jin Xin X Wu Heshui H Huang Haojie H

Theranostics 20200101 3

<b>Rationale</b>: Abnormal expression of programmed death-1 (PD-1) ligand-1(PD-L1) in cancer cells plays a crucial role in cancer immune evasion and progression. The immune checkpoint molecules PD-1 and PD-L1 have been targeted for cancer treatment with significant benefits for cancer patients. However, the response rate is relatively low in certain types of cancer and the underlying mechanism remains poorly understood. Better understanding of the molecular mechanism of PD-L1 expression regulati ...[more]

PMID: 31938049

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Project description:Clear cell renal cell carcinoma (ccRCC), the most common form of kidney cancer, is characterized by elevated glycogen levels and fat deposition. These consistent metabolic alterations are associated with normoxic stabilization of hypoxia-inducible factors (HIFs) secondary to von Hippel-Lindau (VHL) mutations that occur in over 90% of ccRCC tumours. However, kidney-specific VHL deletion in mice fails to elicit ccRCC-specific metabolic phenotypes and tumour formation, suggesting that additional mechanisms are essential. Recent large-scale sequencing analyses revealed the loss of several chromatin remodelling enzymes in a subset of ccRCC (these included polybromo-1, SET domain containing 2 and BRCA1-associated protein-1, among others), indicating that epigenetic perturbations are probably important contributors to the natural history of this disease. Here we used an integrative approach comprising pan-metabolomic profiling and metabolic gene set analysis and determined that the gluconeogenic enzyme fructose-1,6-bisphosphatase 1 (FBP1) is uniformly depleted in over six hundred ccRCC tumours examined. Notably, the human FBP1 locus resides on chromosome 9q22, the loss of which is associated with poor prognosis for ccRCC patients. Our data further indicate that FBP1 inhibits ccRCC progression through two distinct mechanisms. First, FBP1 antagonizes glycolytic flux in renal tubular epithelial cells, the presumptive ccRCC cell of origin, thereby inhibiting a potential Warburg effect. Second, in pVHL (the protein encoded by the VHL gene)-deficient ccRCC cells, FBP1 restrains cell proliferation, glycolysis and the pentose phosphate pathway in a catalytic-activity-independent manner, by inhibiting nuclear HIF function via direct interaction with the HIF inhibitory domain. This unique dual function of the FBP1 protein explains its ubiquitous loss in ccRCC, distinguishing FBP1 from previously identified tumour suppressors that are not consistently mutated in all tumours.

Dataset Information

Fructose-1,6-bisphosphatase loss modulates STAT3-dependent expression of PD-L1 and cancer immunity.

Publications

Fructose-1,6-bisphosphatase loss modulates STAT3-dependent expression of PD-L1 and cancer immunity.

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