ISCA2 inhibition decreases HIF and induces ferroptosis in clear cell renal carcinoma.

Clear cell renal cell carcinoma (ccRCC), the most common form of kidney cancer, is typically initiated by inactivation of the von Hippel Lindau (VHL) gene, which results in the constitutive activation of the hypoxia inducible factors, HIF-1α and HIF-2α. Using a high throughput screen, we identify novel compounds that decrease HIF-1/2α levels and induce ferroptosis by targeting Iron Sulfur Cluster Assembly 2 (ISCA2), a component of the late mitochondrial Iron Sulfur Cluster (L-ISC) assembly complex. ISCA2 inhibition either pharmacologically or using siRNA decreases HIF-2α protein levels by blocking iron-responsive element (IRE)-dependent translation, and at higher concentrations, also decreases HIF-1α translation through unknown mechanisms. Additionally, ISCA2 inhibition triggers the iron starvation response, resulting in iron/metals overload and death via ferroptosis. ISCA2 levels are decreased in ccRCC compared to normal kidney, and decreased ISCA2 levels are associated with pVHL loss and with sensitivity to ferroptosis induced by ISCA2 inhibition. Strikingly, pharmacological inhibition of ISCA2 using an orally available ISCA2 inhibitor significantly reduced ccRCC xenograft growth in vivo, decreased HIF-α levels and increased lipid peroxidation, suggesting increased ferroptosis in vivo. Thus, the targeting of ISCA2 may be a promising therapeutic strategy to inhibit HIF-1/2α and to induce ferroptosis in pVHL deficient cells.

Macrophage HIF-1α Is an Independent Prognostic Indicator in Kidney Cancer.

PURPOSE: Clear cell renal cell carcinoma (ccRCC) is frequently associated with inactivation of the von Hippel-Lindau tumor suppressor, resulting in activation of HIF-1α and HIF-2α. The current paradigm, established using mechanistic cell-based studies, supports a tumor promoting role for HIF-2α, and a tumor suppressor role for HIF-1α. However, few studies have comprehensively examined the clinical relevance of this paradigm. Furthermore, the hypoxia-associated factor (HAF), which regulates the HIFs, has not been comprehensively evaluated in ccRCC. EXPERIMENTAL DESIGN: To assess the involvement of HAF/HIFs in ccRCC, we analyzed their relationship to tumor grade/stage/outcome using tissue from 380 patients, and validated these associations using tissue from 72 additional patients and a further 57 patients treated with antiangiogenic therapy for associations with response. Further characterization was performed using single-cell mRNA sequencing (scRNA-seq), RNA-in situ hybridization (RNA-ISH), and IHC. RESULTS: HIF-1α was primarily expressed in tumor-associated macrophages (TAMs), whereas HIF-2α and HAF were expressed primarily in tumor cells. TAM-associated HIF-1α was significantly associated with high tumor grade and increased metastasis and was independently associated with decreased overall survival. Furthermore, elevated TAM HIF-1α was significantly associated with resistance to antiangiogenic therapy. In contrast, high HAF or HIF-2α were associated with low grade, decreased metastasis, and increased overall survival. scRNA-seq, RNA-ISH, and Western blotting confirmed the expression of HIF-1α in M2-polarized CD163-expressing TAMs. CONCLUSIONS: These findings highlight a potential role of TAM HIF-1α in ccRCC progression and support the reevaluation of HIF-1α as a therapeutic target and marker of disease progression.

Transglutaminase-2 promotes metastatic and stem-like phenotypes in osteosarcoma.

Osteosarcoma (OS) is a highly aggressive mesenchymal malignancy and the most common primary bone tumor in the pediatric population. OS frequently presents with or develops distal metastases. Patients with metastatic disease have extremely poor survival rates, thus necessitating improved molecular insights into OS metastatic biology. Utilizing our previously characterized genetically engineered mouse model (GEMM) of metastatic OS, we identified enhanced differential expression of Transglutaminase-2 (TGM2) in metastatic OS. However, the role of TGM2 in sarcoma development and metastatic progression remains largely undefined. To further investigate the role of TGM2 in OS metastasis, we performed both gain- and loss-of-function studies for TGM2 in human and mouse OS cell lines. Our data provide evidence that enhanced expression of TGM2 in metastatic OS contributes to migratory and invasive phenotypes. Besides the effects on metastatic phenotypes, we also observed that TGM2 contributes to OS stem-like properties. In addition, treatment with transglutaminase inhibitors had analogous effects on proliferation and migration to TGM2 knockdown. Finally, in vivo xenograft studies demonstrated that TGM2 functionally alters metastatic potential and survival outcome. Together, these data highlight TGM2 as a pro-metastatic factor in OS and a potential avenue for future therapeutic intervention to inhibit metastatic disease.