Scientists have identified a key dependency in kidney cancer cells lacking the tumor suppressor gene SETD2, which may guide new targeted therapies for this hard-to-treat cancer subtype. The study, published in Cancer Research, reports that SETD2-deficient kidney cancer cells rely heavily on the protein BCL-xL for survival, a vulnerability not shared by cancer cells with intact SETD2.
SETD2 is frequently mutated or lost in clear cell renal cell carcinoma, the most common form of kidney cancer, affecting around 20% to 25% of cases. Tumours with SETD2 loss tend to be more aggressive and resistant to current treatments. Understanding why these cancers benefit from losing SETD2 and how to exploit this change is a priority for researchers.
The team, led by Aguirre de Cubas at MUSC Hollings Cancer Center, used a synthetic lethality approach to identify genetic and protein dependencies specific to SETD2-deficient cells. They found that such cells become highly dependent on BCL-xL, a protein that inhibits programmed cell death and promotes cell survival. Inhibiting BCL-xL selectively induced death in SETD2-deficient kidney cancer cells, while sparing those with normal SETD2 function.
Mitochondrial stress plays a central role in this vulnerability. Normally, mitochondrial DNA (mtDNA) is compartmentalised within mitochondria, but in SETD2-deficient cells, mtDNA leaks into the cytoplasm. This triggers the cGAS-STING pathway, a key component of the innate immune system that detects misplaced DNA and initiates inflammatory responses. The persistent activation of this pathway creates a pro-inflammatory environment within SETD2-deficient cancer cells.
When BCL-xL is inhibited, this inflammatory state intensifies, driving cancer cells into programmed death while potentially increasing their visibility to the immune system. This dual effect enhances the therapeutic potential of targeting BCL-xL in SETD2-deficient kidney cancers.
The findings also provide insight into kidney cancer’s responsiveness to immunotherapy despite its relatively low mutation burden. Unlike other cancers, the inflammatory signals in kidney tumors appear to arise mainly from mitochondrial DNA leakage rather than nuclear micronuclei, refocusing attention on mitochondrial stress as a key factor in tumour immune activity.
Further research will investigate how mitochondrial DNA leakage occurs in SETD2-deficient tumours and whether this mechanism can be manipulated to improve treatment responses. There is also interest in combining BCL-xL inhibitors with immune checkpoint blockade therapies to enhance the immune system’s ability to target these cancers effectively.
While the current results remain preclinical, the study lays a solid foundation for subsequent translational research. De Cubas and his team are expanding their laboratory capacity to explore these pathways in greater detail and move toward clinical applications.
"The effect we see in SETD2-mutant tumours from targeting BCL-xL is strong and specific," said de Cubas. "Understanding this biology better could lead to more precise treatments for patients with limited options."
This discovery marks progress in addressing a challenging subtype of kidney cancer by targeting a cancer cell’s acquired weaknesses rather than the mutations driving tumour growth alone. It opens new avenues not only for drug development but also for enhancing immunotherapy effectiveness in patients facing poor prognoses.
