Biology subjects

Hafizi, S.

Publications and source records attributed to Hafizi, S..

3 recordsLinked to original sources

bioRxiv2024

Hypoxia inducible factors drive miRNA-mediated downregulation of L2HGDH and HIF1A in clear cell renal cancer independent of 14q deletion

Clear cell renal cell carcinoma (ccRCC) is characterized by pseudohypoxic signaling as well as metabolic and epigenetic aberrations of increasing severity during its pathogenesis and progression. Upon identifying that the markedly lower expression of L2HGDH and HIF1A in ccRCC tumors is not explained only by 14q deletion (40% of ccRCC), we sought to elucidate the mechanisms underscoring their down-regulation independent of 14q deletion, given the marked translational and scientific importance. While lower L2HGDH was found to portend a strikingly worse prognosis in a multivariate survival analysis of ccRCC patients (n=509; TCGA) highlighting its translational importance, the lower expression of HIF1A in ccRCC despite the upregulated HIF1 protein (secondary to VHL loss) is of significant scientific interest. Using a comprehensive array of in vitro assays with genetic manipulation, clinicogenomic bioinformatic analyses of large ccRCC datasets, and the Cdh16-Cre Vhl-fl mouse model with kidney specific Vhl-loss, we demonstrate that the downregulation of both L2HGDH and HIF1A in ccRCC is driven by the hypoxia-inducible factors via miR21-3p and miR155-5p, respectively, during pathogenesis and progression. In doing so, we unveil a conserved inhibitory feedback loop for HIF1A in ccRCC (HIFs[->]miR155[->]HIF1A), providing a mechanistic explanation for HIF1A downregulation despite elevated HIF1 protein. Furthermore, and most importantly, we show that inhibition of hypoxia-inducible factors reverses the adverse loss of L2HGDH and hydroxymethylcytosine in ccRCC, implicating both HIF2 and HIF1 in these metabolic-epigenetic aberrations. Translational StatementThis study demonstrates that hypoxia-inducible factors (HIFs) drive early and sustained metabolic and epigenetic dysregulation in clear cell renal cell carcinoma (ccRCC). Notably, these aberrations begin early in carcinogenesis. We show that inhibition of HIFs can reverse these pathological changes - most significantly, restoring levels of 5-hydroxymethylcytosine, a key epigenetic marker lost in ccRCC due to metabolic inhibition of TET enzymes. Our findings support the integration of HIF2 inhibition earlier in the therapeutic approach for advanced ccRCC. Moreover, the data suggest that dual inhibition of HIF2 and HIF1 - particularly in tumors with high expression of both factors - may yield a more robust reversal of epigenetic abnormalities and merits further investigation. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=189 HEIGHT=200 SRC="FIGDIR/small/625494v2_ufig1.gif" ALT="Figure 1"> View larger version (85K): org.highwire.dtl.DTLVardef@a75aborg.highwire.dtl.DTLVardef@b36704org.highwire.dtl.DTLVardef@3057c4org.highwire.dtl.DTLVardef@1d24074_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2022

Transient regulation of focal adhesion via Tensin3 is required for nascent oligodendrocyte differentiation

The differentiation of oligodendroglia from oligodendrocyte precursor cells (OPCs) to complex and extensive myelinating oligodendrocytes (OLs) is a multistep process that involves largescale morphological changes with significant strain on the cytoskeleton. While key chromatin and transcriptional regulators of differentiation have been identified, their target genes responsible for the morphological changes occurring during OL myelination are still largely unknown. Here, we show that the regulator of focal adhesion, Tensin3 (Tns3), is a direct target gene of Olig2, Chd7, and Chd8, transcriptional regulators of OL differentiation. Tns3 is transiently upregulated and localized to cell processes of immature OLs, together with integrin-{beta}1, a key mediator of survival at this transient stage. Constitutive Tns3 loss-of-function leads to reduced viability in mouse and humans, with surviving knockout mice still expressing Tns3 in oligodendroglia. Acute deletion of Tns3 in vivo, either in postnatal neural stem cells (NSCs) or in OPCs, leads to a two-fold reduction in OL numbers. We find that the transient upregulation of Tns3 is required to protect differentiating OPCs and immature OLs from cell death by preventing the upregulation of p53, a key regulator of apoptosis. Altogether, our findings reveal a specific time window during which transcriptional upregulation of Tns3 in immature OLs is required for OL differentiation likely by mediating integrin-{beta}1 survival signaling to the actin cytoskeleton as OL undergo the large morphological changes required for their terminal differentiation.

neuroscience↗

bioRxiv2020

Functional succinate dehydrogenase deficiency is a pathognomonic adverse feature of clear cell renal cancer

BackgroundReduced succinate dehydrogenase (SDH) activity resulting in adverse succinate accumulation was previously thought to be relevant only in 0.05-0.5% of kidney cancers associated with germline SDH mutations (categorized SDH-deficient Renal Cell Carcinoma in the 2016 WHO classification) ResultsWe show that under-expression of SDH subunits resulting in accumulation of oncogenic succinate is a common feature in clear cell renal cell carcinoma (ccRCC) tumors during pathogenesis and progression, with a marked adverse impact on survival in a large cohort (n=516) of ccRCC patients. From a mechanistic standpoint, we show that von Hippel-Lindau (VHL) loss induced hypoxia-inducible factor (HIF) dependent upregulation of mir-210 in ccRCC causes direct inhibition of the SDHD transcript. We demonstrate that reduced expression of SDH subunits is associated with genome-wide increase in methylation and enhancement of epithelial mesenchymal transition (EMT) in ccRCC tumors, consistent with succinate-induced inhibition of TET activity and increase in invasiveness/ migratory ability of ccRCC cells. TET-2 inhibition-induced global regulatory DNA hypermethylation drives SDH loss-induced enrichment of EMT. SDH subunits under-expression had a striking association with CDHI (E-cadherin) loss in ccRCC tumors, in keeping with succinate-induced CDH1 hypermethylation and under-expression in ccRCC cells. Next, in conformity with recombinant TET-2 fluorescence quenching dynamics with succinate and ascorbic acid (AA, a TET enzyme co-factor), AA treatment led to reversal of succinate-induced inhibition of TET activity, CDH1 hypermethylation and under-expression, as well as enhanced invasiveness in ccRCC cells. Furthermore, using immunohistochemical analysis and artificial intelligence quantitation, we report that ccRCC is characterized by a marked loss of ascorbic acid transporter SLC23A1 [median percent positive cells in ccRCC primary tumors (n=104) and normal kidney cortex (n=7) was 0.7 and 32.4 respectively; p=0.0012]. Lower SLC23A1 was associated with worse survival in ccRCC (TCGA). Lastly, intravenous AA significantly prolonged survival in a metastatic ccRCC xenograft model with increased succinate and reduced SLC23A1 expression. ConclusionsTaken together, these findings strongly indicate that functional SDH deficiency is a pathognomonic adverse feature of ccRCC (which accounts for [~]80% of all kidney cancers), and that the WHO category SDH-deficient RCC should be re-named SDH germline mutation-associated RCC. Furthermore, oncogenic accumulation of succinate can be abrogated by TET modulation with AA. STATEMENT OF SIGNIFICANCEIn this study, we show that under-expression of succinate dehydrogenase (SDH) subunits resulting in the accumulation of oncogenic succinate is a common, adverse, epigenetic modulating feature occurring in a vast majority of clear cell renal cell carcinoma (ccRCC), during pathogenesis and progression. Functional SDH deficiency is therefore a pathognomonic feature of ccRCC (which accounts for [~]80% of all kidney cancers), and not just limited to the 0.05-0.5% of kidney cancer patients with germline SDH mutations. Based on the findings reported, we propose that the SDH-deficient RCC category in the 2016 WHO classification of kidney tumors be renamed SDH germline mutation-associated RCC. Furthermore, we demonstrate that oncogenic accumulation of succinate in ccRCC can be countered by TET modulation with ascorbic acid, and that ccRCC is characterized by a marked loss of ascorbic acid transporter SLC23A1. O_FIG O_LINKSMALLFIG WIDTH=172 HEIGHT=200 SRC="FIGDIR/small/188433v2_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@728d5eorg.highwire.dtl.DTLVardef@9f2e24org.highwire.dtl.DTLVardef@8e7011org.highwire.dtl.DTLVardef@15f8d33_HPS_FORMAT_FIGEXP M_FIG Graphical abstract depicting the consequential adverse downregulation of Succinate Dehydrogenase in ccRCC and its central role in oxidative phosphorylation C_FIG

cancer biology↗