Hypoxia-Inducible Factor-2α as a Novel Target in Renal Cell Carcinoma

Exploring the anticancer potential of hydrogen sulfide and BAY‑876 on clear cell renal cell carcinoma cells: Uncovering novel mutations in VHL and KDR genes among ccRCC patients

The aim of the present study was to determine the cytotoxic effect of BAY-876 and NaSH alone or in combination with sunitinib against the 786-O cell line (renal adenocarcinoma). The IC50 of sunitinib, BAY-876 and NaSH were estimated. Cells were cultured in a 96-well plate and then different concentration of each drug alone was exposed for different incubation time; afterwards, cell cytotoxicity was measured using Cell Counting Kit-8 kit. The IC50 for each drug was used in next experiment to determine the influence of drug combinations. Furthermore, to observe the effect of mutations of few driver genes in development of clear cell renal cell carcinoma (ccRCC), direct sanger sequencing was used to find single nucleotide polymorphisms in exon 1 and exon 13 of tumor suppressor gene Von Hippel Lindau (VHL) and kinase insert domain receptor (KDR) genes respectively in ccRCC formalin fixed paraffin embedded block samples. The results revealed that the IC50 for sunitinib (after 72 h), BAY-876 (after 96 h) and NaSH (after 48 h) was 5.26, 53.56 and 692 µM respectively. The cytotoxic effect of sunitinib and BAY-876, sunitinib and NaSH combinations after 24- and 48-h incubation respectively was significantly higher (P<0.05) compared with the control group as well as to sunitinib group alone. These results proved that each of BAY-876 and NaSH have anticancer effect; thus, they could be used in future for ccRCC treatment purpose. Furthermore, direct sequencing results demonstrated unrecorded mutations of VHL and KDR genes is 43.7 and 31.5% of cases respectively. These findings confirmed the leading role of VHL gene in development of ccRCC and the crucial role of KDR gene in angiogenesis and drug resistance.

FBXO30 functions as a tumor suppressor and an E3 ubiquitin ligase for hZIP1‑mediated HIF‑1α degradation in renal cell carcinoma

Studies on clear cell renal cell carcinoma (ccRCC) are gaining momentum due to its high malignancy and potential to metastasize. F‑box protein 30 (FBXO30) is a member of the F‑box protein family; however, its role and mechanism in cancer remains to be fully elucidated. Western blotting, reverse transcription‑quantitative PCR and immunohistochemsitry were performed to detect the expression levels of FBXO30 in ccRCC tissues and adjacent normal tissues. Tumor biological function assays and animal experiments were conducted to clarify the inhibitory effect of FBXO30 on the progression and metastasis of ccRCC. Protein half‑life assay, MG132 inhibition assay, immunofluorescence assay and co‑immunoprecipitation assay were performed to explore the ubiquitination mechanism of FBXO30 and HIF‑1α. Zinc supplementation assay was used to verify the regulatory relationship between human ZRT, IRT‑like protein 1 (hZIP1), FBXO30 and HIF‑1α. The present study revealed that the expression levels of FBXO30 were lower in ccRCC tissues compared with those in normal adjacent tissues. In addition, FBXO30 inhibited the tumorigenesis and metastatic capacity of ccRCC cells in vivo and in vitro. FBXO30 mediated the ubiquitination and degradation of hypoxia‑inducible factor‑1α (HIF‑1α) in ccRCC cells under normoxia, thereby inhibiting the oncogenic effect of HIF‑1α. Notably, hZIP1 served as an upstream regulator of FBXO30, regulating the expression of FBXO30 and HIF‑1α by recruiting Zn²⁺. In conclusion, the present data suggested that FBXO30 is a novel E3 ubiquitination ligase that can function as a tumor suppressor in ccRCC, and the hZIP1/Zn²⁺/FBXO30/HIF‑1α axis may provide potential biomarkers or therapeutic targets for ccRCC.

The hypoxia-inducible factor-1α in stemness and resistance to chemotherapy in gastric cancer: Future directions for therapeutic targeting

Hypoxia-inducible factor-1α (HIF-1α) is a crucial mediator of intra-tumoral heterogeneity, tumor progression, and unresponsiveness to therapy in tumors with hypoxia. Gastric tumors, one of the most aggressive tumors in the clinic, are highly enriched in hypoxic niches, and the degree of hypoxia is strongly correlated with poor survival in gastric cancer patients. Stemness and chemoresistance in gastric cancer are the two root causes of poor patient outcomes. Based on the pivotal role of HIF-1α in stemness and chemoresistance in gastric cancer, the interest in identifying critical molecular targets and strategies for surpassing the action of HIF-1α is expanding. Despite that, the understanding of HIF-1α induced signaling in gastric cancer is far from complete, and the development of efficacious HIF-1α inhibitors bears various challenges. Hence, here we review the molecular mechanisms by which HIF-1α signaling stimulates stemness and chemoresistance in gastric cancer, with the clinical efforts and challenges to translate anti-HIF-1α strategies into the clinic.

CD70-Targeted Micelles Enhance HIF2α siRNA Delivery and Inhibit Oncogenic Functions in Patient-Derived Clear Cell Renal Carcinoma Cells

The majority of clear cell renal cell carcinomas (ccRCCs) are characterized by mutations in the Von Hippel−Lindau (VHL) tumor suppressor gene, which leads to the stabilization and accumulation of the HIF2α transcription factor that upregulates key oncogenic pathways that promote glucose metabolism, cell cycle progression, angiogenesis, and cell migration. Although FDA-approved HIF2α inhibitors for treating VHL disease-related ccRCC are available, these therapies are associated with significant toxicities such as anemia and hypoxia. To improve ccRCC-specific drug delivery, peptide amphiphile micelles (PAMs) were synthesized incorporating peptides targeted to the CD70 marker expressed by ccRCs and anti-HIF2α siRNA, and the ability of HIF2α-CD27 PAMs to modulate HIF2α and its downstream targets was evaluated in human ccRCC patient-derived cells. Cell cultures were derived from eight human ccRCC tumors and the baseline mRNA expression of HIF2A and CD70, as well as the HIF2α target genes SLC2A1, CCND1, VEGFA, CXCR4, and CXCL12 were first determined. As expected, each gene was overexpressed by at least 63% of all samples compared to normal kidney proximal tubule cells. Upon incubation with HIF2α-CD27 PAMs, a 50% increase in ccRCC-binding was observed upon incorporation of a CD70-targeting peptide into the PAMs, and gel shift assays demonstrated the rapid release of siRNA (>80% in 1 h) under intracellular glutathione concentrations, which contributed to ~70% gene knockdown of HIF2α and its downstream genes. Further studies demonstrated that knockdown of the HIF2α target genes SLC2A1, CCND1, VEGFA, CXCR4, and CXCL12 led to inhibition of their oncogenic functions of glucose transport, cell proliferation, angiogenic factor release, and cell migration by 50−80%. Herein, the development of a nanotherapeutic strategy for ccRCC-specific siRNA delivery and its potential to interfere with key oncogenic pathways is presented.

The Role of Hypoxia-Inducible Factor Isoforms in Breast Cancer and Perspectives on Their Inhibition in Therapy

Simple Summary

In many types of cancers, the activity of the hypoxia-inducible factors enhances hallmarks such as suppression of the immune response, altered metabolism, angiogenesis, invasion, metastasis, and more. As a result of observing these features, HIFs became attractive targets in designing anticancer therapy. The lack of effective breast treatment based on HIFs inhibitors and the elusive role of those factors in this type of cancer raises the concern wheter targeting hypoxia-inducible factors is the right path. Results of the study on breast cancer cell lines suggest the need to consider aspects like HIF-1α versus HIF-2α isoforms inhibition, double versus singular isoform inhibition, different hormone receptors status, metastases, and perhaps different not yet investigated issues. In other words, targeting hypoxia-inducible factors in breast cancers should be preceded by a better understanding of their role in this type of cancer. The aim of this paper is to review the role, functions, and perspectives on hypoxia-inducible factors inhibition in breast cancer.

Abstract

Hypoxia is a common feature associated with many types of cancer. The activity of the hypoxia-inducible factors (HIFs), the critical element of response and adaptation to hypoxia, enhances cancer hallmarks such as suppression of the immune response, altered metabolism, angiogenesis, invasion, metastasis, and more. The HIF-1α and HIF-2α isoforms show similar regulation characteristics, although they are active in different types of hypoxia and can show different or even opposite effects. Breast cancers present several unique ways of non-canonical hypoxia-inducible factors activity induction, not limited to the hypoxia itself. This review summarizes different effects of HIFs activation in breast cancer, where areas such as metabolism, evasion of the immune response, cell survival and death, angiogenesis, invasion, metastasis, cancer stem cells, and hormone receptors status have been covered. The differences between HIF-1α and HIF-2α activity and their impacts are given special attention. The paper also discusses perspectives on using hypoxia-inducible factors as targets in anticancer therapy, given current knowledge acquired in molecular studies.

The Frontline Immunotherapy-Based Treatment of Advanced Clear Cell Renal Cell Carcinoma: Current Evidence and Clinical Perspective

Approximately 400,000 patients are diagnosed with kidney cancer annually worldwide, leading to approximately 170,000 deaths. Renal cell carcinoma (RCC) accounts for more than 90% of kidney cancers. The most common histological subtype is clear cell RCC, which is found in approximately 85% of metastatic RCC cases. The VHL-HIF-VEGF axis is well known; therefore, targeting VEGF has been the mainstay for managing advanced clear cell RCC. Recently, the treatment landscape for advanced clear cell RCC has changed extensively. In particular, immune checkpoint inhibitor-based treatment showed promising results in front-line treatment and became the standard of care. Herein, we review the current evidence on front-line treatment options and discuss the clinical and future perspective.

From Bench to Bedside: How the Tumor Microenvironment Is Impacting the Future of Immunotherapy for Renal Cell Carcinoma

Immunotherapy has revolutionized the treatment landscape for many cancer types. The treatment for renal cell carcinoma (RCC) has especially evolved in recent years, from cytokine-based immunotherapies to immune checkpoint inhibitors. Although clinical benefit from immunotherapy is limited to a subset of patients, many combination-based approaches have led to improved outcomes. The success of such approaches is a direct result of the tumor immunology knowledge accrued regarding the RCC microenvironment, which, while highly immunogenic, demonstrates many unique characteristics. Ongoing translational work has elucidated some of the mechanisms of response, as well as primary and secondary resistance, to immunotherapy. Here, we provide a comprehensive review of the RCC immunophenotype with a specific focus on how preclinical and clinical data are shaping the future of immunotherapy.