Poster Presentation NSW State Cancer Conference 2023

Suppression of the Cystine-Glutamate Transporter SLC7A11/xCT system enhances sensitivity of lung cancer cells to platinum-based drugs. (#124)

Anya Jensen 1 2 3 , George Sharbeen 2 , Zerong Ma 1 3 4 5 , Rosa Mistica Ignacio 1 3 4 , Sze Wing Wong 1 3 4 , Janet Youkhana 2 , John Kokkinos 2 4 , Maria Kavallaris 1 3 4 5 , Phoebe Phillips 2 4 , Joshua McCarroll 1 3 4 5
  1. Children's Cancer Institute, Randwick, NSW, AUS
  2. Pancreatic Cancer Translational Research Group, Adult Cancer Program, Lowy Cancer Research Centre, UNSW Sydney, Sydney, Australia
  3. School of Clinical Medicine, Faculty of Medicine and Health, Sydney, NSW, Australia
  4. Australian Centre for Nanomedicine, UNSW Sydney, Sydney, NSW, Australia
  5. UNSW RNA Institute, UNSW Sydney, Sydney, Australia

Background: Lung cancer is the leading cause of cancer-related death worldwide [1] and presents a significant clinical challenge due to chemoresistance. First-line treatment of lung cancer includes the use of platinum-based chemotherapy drugs (cisplatin, carboplatin). These drugs function by cross-linking DNA to impede cell proliferation, while also inducing the generation of reactive oxygen species (ROS) intracellularly. SLC7A11 has been identified as a pivotal gene involved in tumour metabolism and is highly expressed in cancer cells [2,3]. SLC7A11 is a key regulator of amino acid metabolism and is highly expressed in cancer cells. SLC7A11 protects cells from chemotherapy-induced ROS by promoting glutathione synthesis to stabilize ROS. Sulfasalazine (SSZ), a pharmacological inhibitor of SLC7A11, is already used in clinical settings to treat arthritis. We propose that the inhibition of SLC7A11 function with SSZ or gene-altering small-interfering RNA (siRNA) could enhance the effectiveness of platinum-based chemotherapy in lung cancer cells.

Aims: To determine the effectiveness of SSZ or SLC7A11-siRNA in combination with platinum chemotherapy to inhibit lung cancer cell growth.

Methods: SLC7A11 protein expression was measured using western blotting in human lung cancer cells (A549, H1299, H441, H1975). Lung cancer cell growth in the absence or presence of SSZ (0.5-2mM), cisplatin (1.5-6uM), carboplatin (10-20uM) or oxaliplatin (1-4uM) was examined using trypan blue staining and clonogenic assays. Apoptosis and ROS was measured using Annexin V and CellROX staining and flow cytometry. Glutathione levels were measured using an enzyme assay. SLC7A11-siRNA was delivered to lung cancer cells using Lipofectamine2000®, and cell viability and drug sensitivity assessed by trypan blue staining and Alamar blue drug assays.

Results: Lung cancer cells express SLC7A11. In A549 and H1299 cells, SSZ significantly decreased cell viability and proliferation when used in combination with cisplatin, carboplatin and oxaliplatin (*p≤0.05) compared to drugs alone. Mechanistically, we confirmed a significant depletion of glutathione and its active enzyme facilitator, glutathione peroxidase 4 (GPX4) after SSZ treatment within 24h (*p<0.05) and an increase in apoptosis when used in combination with platinum chemotherapy (**p≤0.01). SLC7A11-siRNA also decreased cell viability (*p<0.05) and sensitised A549 cells to cisplatin treatment (*p≤0.05).

Conclusions/Translational significance: These findings suggest that SLC7A11 is a promising therapeutic gene target to increase the chemosensitivity of platinum-based chemotherapy drugs in lung cancer cells. The addition of SSZ to platinum-based therapies for lung cancer may improve drug efficacy in the clinic to ultimately improve patient survival. It may also lower chemotherapy concentrations required for effective treatment.

  1. Sung, H.; Ferlay, J.; Siegel, R. L.; Laversanne, M.; Soerjomataram, I.; Jemal, A.; Bray, F., Global Cancer Statistics 2020: GLOBOCAN Estimates of Incidence and Mortality Worldwide for 36 Cancers in 185 Countries. CA: A Cancer Journal for Clinicians 2021, 71 (3), 209-249.
  2. Sharbeen, G.; McCarroll, J. A. ... Phillips, P. A., Cancer-Associated Fibroblasts in Pancreatic Ductal Adenocarcinoma Determine Response to SLC7A11 Inhibition. Cancer Res 2021, 81 (13), 3461-3479
  3. Ji, X.; Qian, J.; Rahman, S.; Siska, P. J.; Zou, Y.; Harris, B. K.; Hoeksema, M. D.; Trenary, I. A.; Heidi, C.; Eisenberg, R., xCT (SLC7A11)-mediated metabolic reprogramming promotes non-small cell lung cancer progression. Oncogene 2018, 37 (36), 5007-5019.