Glutathione overproduction mediates lymphoma initiating cells survival and has a sex-dependent effect on lymphomagenesis
Lymphoid tumor patients often exhibit resistance to standard therapies or experience rapid relapse post-remission. Tumor-initiating cells (TICs), a small fraction of the tumor cell population known for their self-renewal capacity and resistance to cancer therapies, likely drive tumor relapse. Tumorigenicity strongly correlates with growth in soft gels and TICs are the only cancer cells capable of growing in soft gels. Targeting pathways critical for TIC survival or growth holds promise for improving cancer treatment outcomes but TIC biology remains poorly understood. Here, we show that culturing lymphoid cells in soft hydrogels triggers reactive oxygen species (ROS) production, leading to non-tumor lymphoid cell death while enabling the survival and proliferation of a subset of lymphoma/leukemia cells, TICs or TIC-like cells. Treatment with the antioxidant N-acetylcysteine inhibits this lethality and even promotes the growth of primary non-tumor lymphoid cells in soft gels. Some lymphoma cells escape ROS-induced lethality by boosting antioxidant glutathione production, a response not seen in non-tumor cells. Reducing glutathione production in lymphoma cells, either through pharmacological inhibition of glutamate cysteine ligase (GCL), the enzyme catalyzing the rate-limiting step in glutathione biosynthesis, or via knockdown of GCLC, the GCL catalytic subunit, sharply decreased cell viability and proliferation in soft gels and tumor growth in immunodeficient mice. Tumor cells from B-cell lymphoma/leukemia patients and {lambda}-MYC mice, a B-cell lymphoma mouse model, overproduce glutathione. Importantly, pharmacological GCL inhibition hindered lymphoma growth in female {lambda}-MYC mice, suggesting that this treatment holds promise as a therapeutic strategy for female lymphoma/leukemia patients.