Publications

<div>Abstract<p>Hypoxia in solid tumors is associated with the development of chemoresistance. Although many studies have focused on the effect of hypoxia on drug-induced apoptosis, the effect of nonapoptotic pathways on hypoxia-induced drug resistance has not been previously investigated. Here, we determined the effects of hypoxia on multiple forms of drug-induced death in human MDA-MB-231 breast carcinoma cells. Clonogenic assays showed that preexposure to hypoxia leads to resistance to various classes of chemotherapeutic agents, including anthracyclines (daunorubicin and doxorubicin), epipodophyllotoxins (etoposide), and anthracenediones (mitoxantrone). Results revealed a high degree of heterogeneity in nuclear and cytoplasmic alterations in response to acute drug exposure; however, the majority of exposed cells displayed morphologic and biochemical changes consistent with drug-induced senescence. Hypoxia decreased only the proportion of cells in the senescent population, whereas the small proportion of cells exhibiting features of apoptosis or mitotic catastrophe were unaffected. Similar results were obtained with human HCT116 colon carcinoma cells, indicating that the protective effect of hypoxia on drug-induced senescence is not unique to MDA-MB-231 cells. Treatment of MDA-MB-231 cells with small interfering RNA targeting the α-subunit of hypoxia-inducible factor-1 (HIF-1), a key regulator of cellular adaptations to hypoxia, prevented hypoxia-induced resistance. HIF-1α small interfering RNA also selectively abolished the hypoxia-induced changes in the senescent population, indicating that the increased survival was due to protection against drug-induced senescence. These results support a requirement for HIF-1 in the adaptations leading to drug resistance and reveal that decreased drug-induced senescence is also an important contributor to the development of hypoxia-induced resistance. [Mol Cancer Ther 2008;7(7):1961–73]</p></div>

There are increased levels of HIF-1alpha in ischemic retina that show temporal and spatial correlation with increased expression of VEGF. These findings are consistent with the hypothesis that HIF-1 plays a role in upregulation of VEGF in ischemic retina.

<p>PDF file - 135K, Figure S2. Efficiency of PLOD2 knockdown in MDA-MB-435 cells.</p>

<div>Abstract<p>Intratumoral hypoxia stimulates enrichment of breast cancer stem cells (BCSC), which are critical for metastasis and patient mortality. Here we report a metabolic adaptation that is required for hypoxia-induced BCSC enrichment and metastasis. Hypoxia-inducible factors coordinately regulate expression of genes encoding phosphoglycerate dehydrogenase (PHGDH) and five downstream enzymes in the serine synthesis pathway and mitochondrial one-carbon (folate) cycle. RNAi-mediated silencing of PHGDH expression in both estrogen receptor–positive and negative breast cancer cells led to decreased NADPH levels, disturbed mitochondrial redox homeostasis, and increased apoptosis, which abrogated BCSC enrichment under hypoxic conditions. PHGDH-deficient cells exhibited increased oxidant levels and apoptosis, as well as loss of BCSC enrichment, in response to treatment with carboplatin or doxorubicin. PHGDH-deficient cells were relatively weakly tumorigenic and tumors that did form were deficient in BCSCs, abolishing metastatic capacity. Our findings highlight a role for PHGDH in the formation of secondary (recurrent or metastatic) tumors, with potential implications for therapeutic targeting of advanced cancers. <i>Cancer Res; 76(15); 4430–42. ©2016 AACR</i>.</p></div>

<p>DUSP9 and DUSP16 reciprocally regulate paclitaxel-induced BCSC enrichment in SUM-149 orthotopic tumors.</p>

<p>Characterization of fibronectin-collagen gels.</p>

<p>Supplementary Figure S1. Analysis of G6PD mRNA expression. Supplementary Figure S2. Analysis of MCF-7 Subclones. Supplementary Figure S3. Effect of PHGDH knockdown on cell growth. Supplementary Figure S4. Effect of carboplatin on cell viability. Supplementary Figure S5. Effect of doxorubicin treatment. Supplementary Figure S6. Clinical correlates.</p>

An interchromosomal insertion in 3 generations of a family was ascertained through two developmentally delayed first cousins. Cytogenetic analysis using G-banding and chromosome painting showed an apparently balanced direct insertion of chromosome 10 material into chromosome 12, ins(12;10)(q15;q21.2q22.1), in the mothers and grandfather of these children. The proposita inherited only the derivative 10 chromosome, resulting in deletion of 10q21.2 --> 22.1 while her cousin inherited only the derivative 12, resulting in duplication of 10q21.2 --> 22.1. A comparison of the proposita with published deletion cases suggests a pattern of anomalies attributable to deletion of the 10q21 --> q22 region: developmental delay, hypotonia, a heart murmur, telecanthus, broad nasal root and ear abnormalities. This is the first report of a nontandem duplication of the 10q21 --> q22 region. The phenotype of the cousin with the duplication does not overlap greatly with published tandem 10q duplications. Finally, this report reaffirms the importance of obtaining family studies of patients with interstitial chromosomal abnormalities.

Abstract Abstract 5039 Chuvash polycythemia, the first hereditary disease associated with dysregulated oxygen sensing, is characterized by homozygous germ-line loss-of-function mutation of VHL (598C>T) resulting in elevated hypoxia inducible factor (HIF)-1 and HIF-2 levels, increased red cell mass and propensity to thrombosis. Organ size is determined by the size and number of cells, and its molecular mechanisms are not fully elucidated. Previous work from several groups demonstrated that cell proliferation is regulated in opposite directions by HIF-1α and HIF-2α. HIF-1α inhibits cell proliferation by displacing C-MYC from the promoter of the cyclin-dependent kinase inhibitor, p21Cip, and inducing its expression, while HIF-2α promotes MYC activity and cell proliferation. We determined the volumes of the liver, spleen, and kidneys and the diameter of the head of the pancreas by computerized tomography in 30 individuals with Chuvash polycythemia and 30 age- and sex-matched Chuvash controls and calculated the ratio of organ volume (or diameter) to body mass. The subjects with Chuvash polycythemia had larger ratios of the liver (P<0.01), spleen (P<0.01), kidneys (P<0.05) and head of the pancreas (P=0.05) than Chuvash controls. To test if HIF contributes to this phenotype, we examined Hif1a+/− mice and wild type littermates. We found that Hif1a+/− mice had larger median ratios of liver to body mass (factor of 1.5, P<0.005) and pancreas to body mass (factor of 1.3, P<0.05) than wild type mice. A hepatocyte size analysis revealed that there was no significant difference between Hif1a+/− and wild type mice. To identify how HIF contributes this phenotype, we performed gene expression profiles in the livers of Hif1a+/− and wild type littermates. The profiling results and subsequent individual confirmation showed that compared to wild type mice, Hif1a+/− mice had 2-fold higher HIF-2α mRNA levels (P<0.05) and 9.5-fold lower hepatic p21Cip mRNA levels (P<0.05). Our results showed that relative to body mass, liver, spleen, kidney and pancreas volumes are increased in Chuvash polycythemia. At least in the liver, this phenotype may result from increased HIF-2α and decreased p21Cip1 levels, leading to increased hepatocyte proliferation. Disclosures No relevant conflicts of interest to declare.