Palbociclib treatment alters nucleotide biosynthesis and glutamine dependency in A549 cells

Lindsey R Conroy; Pawel Lorkiewicz; Liqing He; Xinmin Yin; Xiang Zhang; Shesh N Rai; Brian F Clem

doi:10.1186/s12935-020-01357-x

Palbociclib treatment alters nucleotide biosynthesis and glutamine dependency in A549 cells

Cancer Cell Int. 2020 Jul 1:20:280. doi: 10.1186/s12935-020-01357-x. eCollection 2020.

Authors

Lindsey R Conroy^{1

2}, Pawel Lorkiewicz^{3

4}, Liqing He⁴, Xinmin Yin⁴, Xiang Zhang^{4

5}, Shesh N Rai^{6

7

5}, Brian F Clem^{1

5}

Affiliations

¹ Department of Biochemistry and Molecular Genetics, University of Louisville, Louisville, KY USA.
² Present Address: Department of Neuroscience, University of Kentucky, Lexington, KY USA.
³ Diabetes and Obesity Center, Christina Lee Brown Envirome Institute, Louisville, KY USA.
⁴ Department of Chemistry, Center for Regulatory and Environmental Analytical Metabolomics, University of Louisville, Louisville, KY USA.
⁵ James Graham Brown Cancer Center, Louisville, KY USA.
⁶ Department of Bioinformatics and Biostatistics, University of Louisville, Louisville, KY USA.
⁷ Biostatistics and Bioinformatics Facility, James Graham Brown Cancer Center, University of Louisville, Louisville, KY USA.

Abstract

Background: Aberrant activity of cell cycle proteins is one of the key somatic events in non-small cell lung cancer (NSCLC) pathogenesis. In most NSCLC cases, the retinoblastoma protein tumor suppressor (RB) becomes inactivated via constitutive phosphorylation by cyclin dependent kinase (CDK) 4/6, leading to uncontrolled cell proliferation. Palbociclib, a small molecule inhibitor of CDK4/6, has shown anti-tumor activity in vitro and in vivo, with recent studies demonstrating a functional role for palbociclib in reprogramming cellular metabolism. While palbociclib has shown efficacy in preclinical models of NSCLC, the metabolic consequences of CDK4/6 inhibition in this context are largely unknown.

Methods: In our study, we used a combination of stable isotope resolved metabolomics using [U-¹³C]-glucose and multiple in vitro metabolic assays, to interrogate the metabolic perturbations induced by palbociclib in A549 lung adenocarcinoma cells. Specifically, we assessed changes in glycolytic activity, the pentose phosphate pathway (PPP), and glutamine utilization. We performed these studies following palbociclib treatment with simultaneous silencing of RB1 to define the pRB-dependent changes in metabolism.

Results: Our studies revealed palbociclib does not affect glycolytic activity in A549 cells but decreases glucose metabolism through the PPP. This is in part via reducing activity of glucose 6-phosphate dehydrogenase, the rate limiting enzyme in the PPP. Additionally, palbociclib enhances glutaminolysis to maintain mitochondrial respiration and sensitizes A549 cells to the glutaminase inhibitor, CB-839. Notably, the effects of palbociclib on both the PPP and glutamine utilization occur in an RB-dependent manner.

Conclusions: Together, our data define the metabolic impact of palbociclib treatment in A549 cells and may support the targeting CDK4/6 inhibition in combination with glutaminase inhibitors in NSCLC patients with RB-proficient tumors.

Keywords: Glutaminolysis; Lung cancer; Metabolism; PPP; Palbociclib; RB.

Abstract

Grants and funding