Abstract 3161: PCTK1 driven glutamine metabolic adaptation in brain metastasis

Abstract

Abstract Brain metastasis (BrM) is the most common malignancy of the central nervous system and the median survival time of patients with BrM is less than 1 year. Although recent impressive advances in targeted therapy and immunotherapy enable more effective control of the systemic diseases, the incidence of BrM upon disease recurrence is steadily increasing. Unfortunately, there is no effective treatments for BrM. To surmount this challenge, we have performed an in vivo human kinome screening to uncover novel kinases that promote breast cancer (BC) BrMs in mice and may serve as therapeutic targets. We identified >20 different kinases enriched in BrM lesions of our mouse models and PCTK1 is one of the top “hits”. We transduced PCTK1 expression vector and the control vector into MDA-MB-231 human BC cells to generate 231.PCTK1 and 231.vector cells, respectively. Intra-carotid injection of the 231.PCTK1 cells into mice induced BrM significantly faster with shortened mouse survival than that of the control 231.vector cells, confirming PCTK1 as a BrM-promoting kinase. However, when 231.vector or 231.PCTK1 cells were injected into the mouse’ mammary glands, PCTK1 overexpression did not lead to enhanced primary tumor growth, suggesting that its pro-tumoral functions are BrM-specific. To uncover how PCTK1 promotes BrM but not primary tumor, we examined whether PCTK1 may confer growth advantage in BrM by utilizing the unique metabolic microenvironment of the brain. We analyzed the relationship between PCTK1 gene expression and gene expression of members of the glutamine metabolism pathway in TCGA database. We found that in the brain tumors, such as low-grade glioma, PCTK1 positively correlated with the expression of glutamine metabolizing genes, including glutaminase 1 and 2 (GLS and GLS2). To evaluate whether PCTK1-overexpressing cells can uptake glutamine from the media directly, we cultured 231.PCTK1 and 231.vector cells in low-nutrient BME media plus 5% d.FBS, with addition of different concentrations of glutamine. The PCTK1-overexpressing cells showed a clear growth advantage at glutamine concentrations ranging from 400 μM to 2 mM. Then, we knocked down PCTK1 in MDA-MB-231 cells by shRNAs and found that PCTK1 knocking down reduced the cell proliferation in 5% d.FBS.BME with 500 µM glutamine, a physiological glutamine level in the brain. We measured the expression of GLS, an enzyme that converts glutamine to glutamate, one of the key steps in the glutamine metabolism, and found that knockdown PCTK1 in MDA-MB-231 cells dramatically reduced the GLS expression, which indicates that PCTK1 can modulate glutamine metabolism in cancer cells. In summary, our data suggest that PCTK1 promotes BC BrM, at least partly, through increasing glutamine metabolism. Currently, we are exploring whether targeting PCTK1 or inhibiting glutamine metabolism can deter BrM progression. Our studies may reveal novel therapeutic targets for BrM inhibition. Citation Format: Lin Zhang, Frank Lowery, Chenyu Zhang, Yu-Wen Huang, Ya-Jing Jiang, Yimin Duan, Dihua Yu. PCTK1 driven glutamine metabolic adaptation in brain metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3161.