Biology subjects

Dang, D. K.

Publications and source records attributed to Dang, D. K..

4 recordsLinked to original sources

bioRxiv2020

Epigenetic Modulation of SPCA2 Reverses Epithelial to Mesenchymal Transition in Breast Cancer Cells

The secretory pathway Ca2+-ATPase SPCA2 is a tumor suppressor in triple receptor negative breast cancer (TNBC), a highly aggressive molecular subtype that lacks tailored treatment options. Low expression of SPCA2 in TNBC confers poor survival prognosis in patients. Previous work has established that re-introducing SPCA2 to TNBC cells restores basal Ca2+ signaling, represses mesenchymal gene expression, mitigates tumor migration in vitro and metastasis in vivo. In this study, we examined the effect of histone deacetylase inhibitors (HDACi) in TNBC cell lines. We show that the pan-HDACi vorinostat and the class I HDACi romidepsin induce dose-dependent upregulation of SPCA2 transcript with concurrent downregulation of mesenchymal markers and tumor cell migration characteristic of epithelial phenotype. Silencing SPCA2 abolished the ability of HDACi to reverse epithelial to mesenchymal transition (EMT). Independent of ATPase activity, SPCA2 elevated resting Ca2+ levels to activate downstream components of non-canonical Wnt/Ca2+ signaling. HDACi treatment led to SPCA2-dependent phosphorylation of CAMKII and {beta}-catenin, turning Wnt signaling off. We conclude that SPCA2 mediates the efficacy of HDACi in reversing EMT in TNBC by a novel mode of non-canonical Wnt/Ca2+ signaling. Our findings provide incentive for screening epigenetic modulators that exploit Ca2+ signaling pathways to reverse EMT in breast tumors. Simple SummaryThe triple receptor negative breast cancer subtype, or TNBC, currently has no tailored treatment options. TNBC is highly metastatic, associated with high patient mortality, and disproportionately occurs in Black/African American women where it contributes to racial disparities in health outcomes. Therefore, we focused on new therapeutic approaches to TNBC. We discovered that levels of the Calcium-ATPase SPCA2 are abnormally low in TNBC and that these low levels correlate with poor survival prognosis in patients. Previously, we showed that recombinant SPCA2 prevented TNBC cells from acquiring aggressive mesenchymal properties associated with metastasis both in vitro and in vivo. These findings motivated us to search for drugs that turn the SPCA2 gene back on in TNBC cells. In this study, we show that histone deacetylase inhibitors increase SPCA2 levels, activate Ca2+ signaling and convert cancer cells to a less aggressive epithelial state. These findings could lead to new treatment options for TNBC. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=140 HEIGHT=200 SRC="FIGDIR/small/379685v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@13b2565org.highwire.dtl.DTLVardef@14317forg.highwire.dtl.DTLVardef@1bdbd34org.highwire.dtl.DTLVardef@1d0bd83_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2020

Store Independent Ca2+ Entry Regulates the DNA Damage Response in Breast Cancer Cells

Although the mainstay of treatment for hormone responsive breast tumors is targeted endocrine therapy, many patients develop de novo or acquired resistance and are treated with chemotherapeutic drugs. The vast majority (80%) of estrogen receptor positive tumors also express wild type p53 protein that is a major determinant of the DNA damage response. Tumors that are ER+ and p53WT respond poorly to chemotherapy, although the underlying mechanisms are not completely understood. We describe a novel link between store independent Ca2+ entry (SICE) and resistance to DNA damaging drugs, mediated by the secretory pathway Ca2+-ATPase, SPCA2. In luminal ER+/PR+ breast cancer subtypes, SPCA2 levels are high and correlate with poor survival prognosis. Independent of ion pump activity, SPCA2 elevates baseline Ca2+ levels through SICE and drives cell proliferation. Attenuation of SPCA2 or depletion of extracellular Ca2+ increased mitochondrial ROS production, DNA damage and activation of the ATM/ATR-p53 axis leading to G0/G1 phase cell cycle arrest and apoptosis. Consistent with these findings, SPCA2 knockdown confers chemosensitivity to DNA damaging agents including doxorubicin, cisplatin and ionizing radiation. We conclude that elevated SPCA2 expression in ER+ p53WT breast tumors drives pro-survival and chemotherapy resistance by suppressing the DNA damage response. Drugs that target storeindependent Ca2+ entry pathways may have therapeutic potential in treating receptor positive breast cancer.

cancer biology↗

bioRxiv2018

A Moonlighting Role for SPCA2 in E-cadherin Biogenesis and Suppression of Epithelial-Mesenchymal Transition

Progression of benign tumors to invasive, metastatic cancer requires loss of the cell-adhesion protein E-cadherin. Although intensive efforts have focused on gene repression and silencing mutations, much less is known about posttranslational control of E-cadherin expression in cancer. SPCA2 is a secretory pathway Ca2+-ATPase that is down-regulated in metastatic breast cancer. We show that SPCA2 is tightly co-expressed with epithelial signature genes and required for E-cadherin biogenesis and cell surface expression. Unexpectedly, this function is uncoupled from Ca2+ pumping and mediated by binding to E-cadherin. Loss of SPCA2 is sufficient to disrupt cell-cell adhesion in tumorspheres and elicit mesenchymal gene expression through Hippo-YAP signaling. These findings point to a causal link between low SPCA2 levels and the epithelial-mesenchymal transition required for breast cancer metastasis.\n\nHighlightsO_LISPCA2 is an epithelial marker transcriptionally linked to E-cadherin expression\nC_LIO_LILoss of SPCA2 impairs E-cadherin biogenesis independent of Ca2+ pump activity\nC_LIO_LISPCA2 is required for tumorsphere formation and Hippo-YAP signaling to antagonize epithelial-mesenchymal transition\nC_LIO_LIDown-regulation of SPCA2 in metastatic cancers may contribute to malignancy\nC_LI\n\n\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=168 SRC=\"FIGDIR/small/379586_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (28K):\norg.highwire.dtl.DTLVardef@6b1e14org.highwire.dtl.DTLVardef@83edbborg.highwire.dtl.DTLVardef@16cbc5corg.highwire.dtl.DTLVardef@1c2752a_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2018

NHA2 promotes cyst development in an in vitro model of polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in PKD1 and PKD2 encoding polycystin-1 (PC1) and polycystin-2 (PC2), respectively. The molecular pathways linking polycystins to cyst development in ADPKD are still unclear. Intracystic fluid secretion via ion transporters and channels plays a crucial role in cyst expansion in ADPKD. Unexpectedly, we observed significant and selective up-regulation of NHA2, a member of the SLC9B family of Na+/H+ exchangers that correlated with cyst size and disease severity in ADPKD patients. Using three-dimensional cultures of MDCK cells to model cystogenesis in vitro, we show that ectopic expression of NHA2 is causal to increased cyst size. Induction of PC1 in MDCK cells inhibited NHA2 expression with concordant inhibition of Ca2+ influx through store-dependent and independent pathways, whereas reciprocal activation of Ca2+ influx by a dominant negative, membrane-anchored C-terminal tail fragment of PC1 elevated NHA2. We show that NHA2 is a target of Ca2+/NFAT signaling and is transcriptionally induced by methylxanthine drugs such as caffeine and theophylline, which are contraindicated in ADPKD patients. Finally, we observe robust induction of NHA2 by vasopressin, which is physiologically consistent with increased levels of circulating vasopressin and up-regulation of vasopressin V2 receptors in ADPKD. Our findings have mechanistic implications on the emerging use of vasopressin V2 receptor antagonists such as tolvaptan as safe and effective therapy for PKD and reveal a potential new regulator of transepithelial salt and water transport in the kidney.

physiology↗