Genetic Analysis of Pathways Regulated by the von Hippel-Lindau Tumor Suppressor in Caenorhabditis elegans

The von Hippel-Lindau (VHL) tumor suppressor functions as a ubiquitin ligase that mediates proteolytic inactivation of hydroxylated α subunits of hypoxia-inducible factor (HIF). Although studies of VHL-defective renal carcinoma cells suggest the existence of other VHL tumor suppressor pathways, dysregulation of the HIF transcriptional cascade has extensive effects that make it difficult to distinguish whether, and to what extent, observed abnormalities in these cells represent effects on pathways that are distinct from HIF. Here, we report on a genetic analysis of HIF-dependent and -independent effects of VHL inactivation by studying gene expression patterns in Caenorhabditis elegans. We show tight conservation of the HIF-1/VHL-1/EGL-9 hydroxylase pathway. However, persisting differential gene expression in hif-1 versus hif-1; vhl-1 double mutant worms clearly distinguished HIF-1–independent effects of VHL-1 inactivation. Genomic clustering, predicted functional similarities, and a common pattern of dysregulation in both vhl-1 worms and a set of mutants (dpy-18, let-268, gon-1, mig-17, and unc-6), with different defects in extracellular matrix formation, suggest that dysregulation of these genes reflects a discrete HIF-1–independent function of VHL-1 that is connected with extracellular matrix function

Dependency of NELF-E-SLUG-KAT2B epigenetic axis in breast cancer carcinogenesis.

Cancer cells undergo transcriptional reprogramming to drive tumor progression and metastasis. Using cancer cell lines and patient-derived tumor organoids, we demonstrate that loss of the negative elongation factor (NELF) complex inhibits breast cancer development through downregulating epithelial-mesenchymal transition (EMT) and stemness-associated genes. Quantitative multiplexed Rapid Immunoprecipitation Mass spectrometry of Endogenous proteins (qPLEX-RIME) further reveals a significant rewiring of NELF-E-associated chromatin partners as a function of EMT and a co-option of NELF-E with the key EMT transcription factor SLUG. Accordingly, loss of NELF-E leads to impaired SLUG binding on chromatin. Through integrative transcriptomic and genomic analyses, we identify the histone acetyltransferase, KAT2B, as a key functional target of NELF-E-SLUG. Genetic and pharmacological inactivation of KAT2B ameliorate the expression of EMT markers, phenocopying NELF ablation. Elevated expression of NELF-E and KAT2B is associated with poorer prognosis in breast cancer patients, highlighting the clinical relevance of our findings. Taken together, we uncover a crucial role of the NELF-E-SLUG-KAT2B epigenetic axis in breast cancer carcinogenesis

Pathways regulated by the von Hippel-Lindau tumor suppressor protein (pVHL)

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The Curious Incident Of 3 Melanomas And Their Possible Origins – A Case Report and Review of Literature (Withdrawn article)

Background: We describe an unusual case of 2 intra-parenchymal breast melanomas with a concomitant subcutaneous melanoma in the ipsilateral upper limb and no definite primary lesion.Case Report: Our patient is a 40-year-old Chinese female who presented with a breast lump in her left breast for which excision biopsy showed melanoma. A PET-CT revealed a second lesion in her breast. A left upper arm nodule with no overlying skin changes was also noted. She underwent a mastectomy and excision biopsy of the upper arm nodule. Histology showed that the second breast lesion was also a melanoma, while the arm nodule contained melanoma cells within a fibrous capsule.Conclusion: The presence of a melanoma in the breast should prompt a close and meticulous search for a primary lesion and potential signs of metastasis. Encapsulated subcutaneous nodules can be attributed to replaced lymph nodes or subcutaneous melanoma which can be either primary dermal melanoma or metastasis from an unknown primary

The curious incident of 3 melanomas and their possible origins—A case report and review of literature

Background: We describe an unusual case of 2 intra-parenchymal breast melanomas with a concomitant subcutaneous melanoma in the ipsilateral upper limb and no definite primary lesion. Case report: Our patient is a 40-year-old Chinese female who presented with a breast lump in her left breast for which excision biopsy showed melanoma. A PET-CT revealed a second lesion in her breast. A left upper arm nodule with no overlying skin changes was also noted. She underwent a mastectomy and excision biopsy of the upper arm nodule. Histology showed that the second breast lesion was also a melanoma, while the arm nodule contained melanoma cells within a fibrous capsule. Conclusion: The presence of a melanoma in the breast should prompt a close and meticulous search for a primary lesion and potential signs of metastasis. Encapsulated subcutaneous nodules can be attributed to replaced lymph nodes or subcutaneous melanoma which can be either primary dermal melanoma or metastasis from an unknown primary

Contrasting Properties of Hypoxia-Inducible Factor 1 (HIF-1) and HIF-2 in von Hippel-Lindau-Associated Renal Cell Carcinoma

Defective function of the von Hippel-Lindau (VHL) tumor suppressor ablates proteolytic regulation of hypoxia-inducible factor α subunits (HIF-1α and HIF-2α), leading to constitutive activation of hypoxia pathways in renal cell carcinoma (RCC). Here we report a comparative analysis of the functions of HIF-1α and HIF-2α in RCC and non-RCC cells. We demonstrate common patterns of HIF-α isoform transcriptional selectivity in VHL-defective RCC that show consistent and striking differences from patterns in other cell types. We also show that HIF-α isoforms display unexpected suppressive interactions in RCC cells, with enhanced expression of HIF-2α suppressing HIF-1α and vice-versa. In VHL-defective RCC cells, we demonstrate that the protumorigenic genes encoding cyclin D1, transforming growth factor alpha, and vascular endothelial growth factor respond specifically to HIF-2α and that the proapoptotic gene encoding BNip3 responds positively to HIF-1α and negatively to HIF-2α, indicating that HIF-1α and HIF-2α have contrasting properties in the biology of RCC. In keeping with this, HIF-α isoform-specific transcriptional selectivity was matched by differential effects on the growth of RCC as tumor xenografts, with HIF-1α retarding and HIF-2α enhancing tumor growth. These findings indicate that therapeutic approaches to targeting of the HIF system, at least in this setting, will need to take account of HIF isoform-specific functions

Sensitivity of VHL-1–Regulated Genes to Defects in Extracellular Matrix-Associated Proteins

<div><p>RNase protection assays showing altered expression of VHL-1–regulated genes that are HIF-1 independent (upper six panels) and HIF-1 dependent (F22B5.4) in worms bearing mutations affecting (A) procollagen prolyl and lysyl hydroxylases and (B) other extracellular matrix-associated proteins. A common pattern of upregulation is observed in <i>hif-1; vhl-1, vhl-1, dpy-18, let-268, gon-1, mig-17,</i> and <i>unc-6</i> worms but not other mutants. This contrasts with the HIF-1–dependent gene F22B5.4, which is upregulated in <i>vhl-1</i> worms but none of the other mutants.</p> <p>(C) RNase protection assay for C01B4.9 illustrating DPY-18–mediated changes in expression that are independent of HIF-1.</p></div

Responses of VHL-1–Dependent, HIF-1–Independent Genes to <i>egl-9</i> Inactivation, Hypoxia, and 2-Oxoglutarate Dioxygenase Inhibitors

<p>RNase protection assays showing regulation of VHL-1–dependent, HIF-1–independent genes by (A) EGL-9 and hypoxia and (B) pharmacological inhibitors of 2-oxoglutarate dioxygenases: DIP and DMOG. None of the genes is regulated by EGL-9, but two genes (C01B4.7 and C01B4.8) show modest induction by hypoxia, DIP, and DMOG.</p