The glutathione redox system is essential to prevent ferroptosis caused by impaired lipid metabolism in clear cell renal cell carcinoma

Abstract

Metabolic reprogramming is a prominent feature of clear cell renal cell carcinoma (ccRCC). Here we investigated metabolic dependencies in a panel of ccRCC cell lines using nutrient depletion, functional RNAi screening and inhibitor treatment. We found that ccRCC cells are highly sensitive to the depletion of glutamine or cystine, two amino acids required for glutathione (GSH) synthesis. Moreover, silencing of enzymes of the GSH biosynthesis pathway or glutathione peroxidases, which depend on GSH for the removal of cellular hydroperoxides, selectively reduced viability of ccRCC cells but did not affect the growth of non-malignant renal epithelial cells. Inhibition of GSH synthesis triggered ferroptosis, an iron-dependent form of cell death associated with enhanced lipid peroxidation. VHL is a major tumour suppressor in ccRCC and loss of VHL leads to stabilisation of hypoxia inducible factors HIF-1α and HIF-2α. Restoration of functional VHL via exogenous expression of pVHL reverted ccRCC cells to an oxidative metabolism and rendered them insensitive to the induction of ferroptosis. VHL reconstituted cells also exhibited reduced lipid storage and higher expression of genes associated with oxidiative phosphorylation and fatty acid metabolism. Importantly, inhibition of β-oxidation or mitochondrial ATP-synthesis restored ferroptosis sensitivity in VHL reconstituted cells. We also found that inhibition of GSH synthesis blocked tumour growth in a MYC-dependent mouse model of renal cancer. Together, our data suggest that reduced fatty acid metabolism due to inhibition of β-oxidation renders renal cancer cells highly dependent on the GSH/GPX pathway to prevent lipid peroxidation and ferroptotic cell death.

Frizzled-7 Identifies Platinum Tolerant Ovarian Cancer Cells Susceptible to Ferroptosis

“…The expression of GSR was also higher in TMZ-resistant compared to sensitive cells and silencing GSR in drug-resistant cells improved sensitivity to TMZ or cisplatin (46). Similar results were reported in clear cell renal carcinoma, where silencing the GSH biosynthesis pathway was shown to trigger ferroptosis (47). Thus, modulation of redox homeostasis by GSH/GSR appears to be an important key modulating sensitivity of cancer cells to chemotherapy (46).…”

HIF-2α drives an intrinsic vulnerability to ferroptosis in clear cell renal cell carcinoma

“…Compared with two control cell lines, immortalized renal tubule cell line HK-2 and RTCC line BFTC909, all four ccRCC cell lines were more sensitive to GPX4 inhibitors (Figure 1F). These results are consistent with previous characterization of the sensitivity to glutathione depletion or treatment with erastin, a system XC -(SLC7A11) inhibitor and a moderate ferroptosis inducer, within the NCI-60 cancer cell lines [28,29]. shRNA-mediated GPX4 knockdown significantly reduced the viability of 786-O, 769-P and OS-RC2 cells (Figure S1C), suggesting a genetic dependency on GPX4.…”

“…While the genetic etiology of ccRCC has been illuminated, the lack of actionable targets underscores the pressing need for novel biological insights. Here, our CTRP analyses, along with previous characterizations, link ccRCC to a unique dependency on GPX4 [28,29]. Given GPX4's role in selectively detoxifying lipid hydroperoxides, and that GPX4 inhibition triggers ferroptotic cell death (ferroptosis) [28], we postulate that ccRCC cells are intrinsically susceptible to ferroptosis, and targeting GPX4 represents a therapeutic opportunity in this devastating disease.…”

“…While ferroptotic cell death was first demonstrated in the context of selective sensitivity in fibroblasts engineered with forced expression of an oncogenic allele of HRAS [47, 92], our work underscores a prominent example of "oncogenesis-associated ferroptosis susceptibility" in human cancers. The involvement of HIF-2a in ferroptosis was indirectly supported by a recent report showing that pVHL restoration reverted the sensitivity to erastin and L-buthionine-S,R-sulfoximine (BSO) in RCC4 cells, although the mechanisms mediating pVHL's action was not elucidated [29], and nonferroptotic contributions to death by these two agents are suggested by the partial rescue using ferrostatin-1. Here we report that HIF-2a selectively enriches PUFAs rather than SFA/MUFAs, up-regulates the abundances of PUFA-TAGs as well as PUFA-phospholipids, and induces a GPX4-dependent, ferroptosis-susceptible state in ccRCC cells.…”

Ferroptosis is programmed by the coordinated regulation of glutathione and iron metabolism by BACH1

“…Slc7a11 encodes a component of system x c - (cystine/glutamine transporter) (Sato et al, 2005, Sato et al, 2000) and a well-known regulator of ferroptosis (Jiang et al, 2015). Gclm and Gclc encode glutamate-cysteine ligase modifier and catalytic subunits (Fan et al, 2012, Telorack et al, 2016), both considered to suppress ferroptosis by GSH synthesis (Miess et al, 2018, Stockwell et al, 2017). These genes for the pathway of GSH synthesis are also considered to be targets of BACH1 (Warnatz et al, 2011).…”