Role and regulation of coordinately expressed de novo purine biosynthetic enzymes PPAT and PAICS in lung cancer.

Moloy T Goswami,Sooryanarayana Varambally,Arul M Chinnaiyan,Nallasivam Palanisamy,David G Beer,Balabhadrapatruni V.S.K Chakravarthi,Shannon L Carskadon,Guoan Chen,Sharath K Anand,Dafydd G Thomas,Satya S Pathi,Thomas J Giordano

doi:10.18632/oncotarget.4352

Abstract

Cancer cells exhibit altered metabolism including aerobic glycolysis that channels several glycolytic intermediates into de novo purine biosynthetic pathway. We discovered increased expression of phosphoribosyl amidotransferase (PPAT) and phosphoribosylaminoimidazole carboxylase, phosphoribosylaminoimidazole succinocarboxamide synthetase (PAICS) enzymes of de novo purine biosynthetic pathway in lung adenocarcinomas. Transcript analyses from next-generation RNA sequencing and gene expression profiling studies suggested that PPAT and PAICS can serve as prognostic biomarkers for aggressive lung adenocarcinoma. Immunohistochemical analysis of PAICS performed on tissue microarrays showed increased expression with disease progression and was significantly associated with poor prognosis. Through gene knockdown and over-expression studies we demonstrate that altering PPAT and PAICS expression modulates pyruvate kinase activity, cell proliferation and invasion. Furthermore we identified genomic amplification and aneuploidy of the divergently transcribed PPAT-PAICS genomic region in a subset of lung cancers. We also present evidence for regulation of both PPAT and PAICS and pyruvate kinase activity by L-glutamine, a co-substrate for PPAT. A glutamine antagonist, 6-Diazo-5-oxo-L-norleucine (DON) blocked glutamine mediated induction of PPAT and PAICS as well as reduced pyruvate kinase activity. In summary, this study reveals the regulatory mechanisms by which purine biosynthetic pathway enzymes PPAT and PAICS, and pyruvate kinase activity is increased and exposes an existing metabolic vulnerability in lung cancer cells that can be explored for pharmacological intervention.

Highlights

Lung cancer is the leading cause of cancer-related deaths globally [1] with non-small cell lung cancer (NSCLC) accounting for 80% of all lung cancers [2, 3]
De novo purine biosynthetic pathway genes are overexpressed in lung cancers The de novo purine biosynthetic pathway involves multiple enzymatic steps that convert 5-phosphoribosyl-1-pyrophosphate (PRPP) to inosine monophosphate (IMP), a precursor for adenosine monophosphate (AMP) and guanosine monophosphate (GMP) production
Our analysis showed that phosphoribosyl amidotransferase (PPAT) and phosphoribosylaminoimidazole succinocarboxamide synthetase (PAICS) are highly e xpressed in the solid type of adenocarcinoma (Supplementary Fig. S2C) [35]

Summary

Introduction

Lung cancer is the leading cause of cancer-related deaths globally [1] with non-small cell lung cancer (NSCLC) accounting for 80% of all lung cancers [2, 3]. In the United States, the overall 5-year survival rate of lung cancer patients is 16% and more than 50% of the cases are diagnosed at advanced stages where curative treatment is not possible. Genomic and gene expression-based characterizations have resulted in improved molecular subtyping of lung cancer and identification of driver mutations including epidermal growth factor receptor (EGFR10–30%), Kirsten rat sarcoma viral oncogene homolog (KRAS-15–30%), and fibroblast growth factor receptor 1 (FGFR1-20%), among others [4, 5]. Lung cancer patients harboring ALK gene fusions treated with crizotinib show similar positive response [7, 8]. Identification of fusions of CD74-NRG1 that activate HER2:HER3 signaling offered therapeutic possibilities for intractable mucinous lung cancers [9, 10]. Well-defined molecular stratification has become essential for the development of targeted treatment for specific molecular subtypes of cancers and personalized therapy

Methods

Results

Conclusion