Combination therapy with mTOR and PI3 kinase inhibitors is broadly synergistic in a wide variety of endometrial cancer cells

Dysregulation of mammalian target of rapamycin (mTOR) signaling has been found in many human tumors, including endometrial cancer, and mTOR inhibitors have been utilized in clinical trials as targeted therapies with only limited success. Herein we identify a viable treatment alternative that overcomes temsirolimus-induced AKT phosphorylation in endometrial cancer. Our data suggest temsirolimus and BEZ235 inhibit different components of the AKT/mTOR signaling pathway to accomplish synergistic pathway inhibition, which is necessary for therapeutic efficacy to abrogate the increased signaling through AKT that occurs with mTOR inhibition alon

BCCIP regulates homologous recombination by distinct domains and suppresses spontaneous DNA damage

Homologous recombination (HR) is critical for maintaining genome stability through precise repair of DNA double-strand breaks (DSBs) and restarting stalled or collapsed DNA replication forks. HR is regulated by many proteins through distinct mechanisms. Some proteins have direct enzymatic roles in HR reactions, while others act as accessory factors that regulate HR enzymatic activity or coordinate HR with other cellular processes such as the cell cycle. The breast cancer susceptibility gene BRCA2 encodes a critical accessory protein that interacts with the RAD51 recombinase and this interaction fluctuates during the cell cycle. We previously showed that a BRCA2- and p21-interacting protein, BCCIP, regulates BRCA2 and RAD51 nuclear focus formation, DSB-induced HR and cell cycle progression. However, it has not been clear whether BCCIP acts exclusively through BRCA2 to regulate HR and whether BCCIP also regulates the alternative DSB repair pathway, non-homologous end joining. In this study, we found that BCCIP fragments that interact with BRCA2 or with p21 each inhibit DSB repair by HR. We further show that transient down-regulation of BCCIP in human cells does not affect non-specific integration of transfected DNA, but significantly inhibits homology-directed gene targeting. Furthermore, human HT1080 cells with constitutive down-regulation of BCCIP display increased levels of spontaneous single-stranded DNA (ssDNA) and DSBs. These data indicate that multiple BCCIP domains are important for HR regulation, that BCCIP is unlikely to regulate non-homologous end joining, and that BCCIP plays a critical role in resolving spontaneous DNA damage

Knockdown of MTDH increases drug sensitivity to HDAC inhibitor and TRAIL combination treatment in endometrial cancer cells

Understanding the molecular mechanisms of chemoresistance is vital to design therapies to restore chemosensitivity. MTDH mediates drug resistance by regulating expression of genes required for the control of apoptosis and cell cycle. These findings indicate that sensitivity to chemotherapy agents and combination treatment with HDAC inhibitor and TRAIL can be restored by manipulating MTDH, and hence depletion of MTDH is a potentially novel avenue for effective cancer therapy

The combination of Paclitaxel and Gefitinib inhibits endometrial cancer cells by inducing mitotic catastrophe: proof of principle for dual therapy in endometrial cancer

Serous uterine endometrial cancer is a lethal disease for which new therapeutic regimens are urgently needed. Combinations of chemotherapeutic agents and small molecule growth factor inhibitors have demonstrated activity in cancers from other sites. Our objective was to determine whether such a combination using Paclitaxel and Gefitinib could be active in serous endometrial cancer cells

25-Hydroxyvitamin D and Vitamin D Binding Protein Levels in Patients With Primary Hyperparathyroidism Before and After Parathyroidectomy

Objective: To evaluate vitamin D binding protein and free 25-hydroxyvitamin D [25(OH)D] levels in healthy controls compared to primary hyperparathyroidism (PHPT) patients, and to examine PHPT before and after surgery.Methods: Seventy-five PHPT patients and 75 healthy age, gender, and body mass index (BMI) -matched control subjects were examined. In addition, 25 PHPT patients underwent parathyroidectomy and had a 3-month follow up visit. Levels of total and free 25(OH)D, DBP, and intact parathyroid hormone (iPTH) were determined before and 3 months after surgery.Results: There was no significant difference in age and BMI between PHPT patients and controls. Levels of 25(OH)D and DBP were lower in PHPT patients compared to controls (p < 0.01). There was no significant difference in calculated free and bioavailable 25(OH)D levels between PHPT patients and controls. Calcium and iPTH levels decreased to normal but DBP and DBP-bound-25(OH)D increased (P < 0.001) after parathyroidectomy. Levels of DBP were inversely correlated with iPTH (r = −0.406, P < 0.001) and calcium levels (r = −0.423, P < 0.001).Conclusion: Serum DBP levels were lower in patients with PHPT and parathyroidectomy restored DBP levels. We suggest that lower DBP levels is one of contributing mechanisms of low total 25(OH)D in PTHP patients and the total 25(OH)D levels might not reflect true vitamin D status in PHPT patients

Knockdown of MTDH Sensitizes Endometrial Cancer Cells to Cell Death Induction by Death Receptor Ligand TRAIL and HDAC Inhibitor LBH589 Co-Treatment

Understanding the molecular underpinnings of chemoresistance is vital to design therapies to restore chemosensitivity. In particular, metadherin (MTDH) has been demonstrated to have a critical role in chemoresistance. Over-expression of MTDH correlates with poor clinical outcome in breast cancer, neuroblastoma, hepatocellular carcinoma and prostate cancer. MTDH is also highly expressed in advanced endometrial cancers, a disease for which new therapies are urgently needed. In this present study, we focused on the therapeutic benefit of MTDH depletion in endometrial cancer cells to restore sensitivity to cell death. Cells were treated with a combination of tumor necrosis factor-α-related apoptosis-inducing ligand (TRAIL), which promotes death of malignant cells of the human reproductive tract, and histone deacetylase (HDAC) inhibitors, which have been shown to increase the sensitivity of cancer cells to TRAIL-induced apoptosis. Our data indicate that depletion of MTDH in endometrial cancer cells resulted in sensitization of cells that were previously resistant in response to combinatorial treatment with TRAIL and the HDAC inhibitor LBH589. MTDH knockdown reduced the proportion of cells in S and increased cell arrest in G2/M in cells treated with LBH589 alone or LBH589 in combination with TRAIL, suggesting that MTDH functions at the cell cycle checkpoint to accomplish resistance. Using microarray technology, we identified 57 downstream target genes of MTDH, including calbindin 1 and galectin-1, which may contribute to MTDH-mediated therapeutic resistance. On the other hand, in MTDH depleted cells, inhibition of PDK1 and AKT phosphorylation along with increased Bim expression and XIAP degradation correlated with enhanced sensitivity to cell death in response to TRAIL and LBH589. These findings indicate that targeting or depleting MTDH is a potentially novel avenue for reversing therapeutic resistance in patients with endometrial cancer

A covalently bound inhibitor triggers EZH2 degradation through CHIP‐mediated ubiquitination

Abstract Enhancer of zeste homolog 2 (EZH2) has been characterized as a critical oncogene and a promising drug target in human malignant tumors. The current EZH2 inhibitors strongly suppress the enhanced enzymatic function of mutant EZH2 in some lymphomas. However, the recent identification of a PRC2‐ and methyltransferase‐independent role of EZH2 indicates that a complete suppression of all oncogenic functions of EZH2 is needed. Here, we report a unique EZH2‐targeting strategy by identifying a gambogenic acid (GNA) derivative as a novel agent that specifically and covalently bound to Cys668 within the EZH2‐SET domain, triggering EZH2 degradation through COOH terminus of Hsp70‐interacting protein (CHIP)‐mediated ubiquitination. This class of inhibitors significantly suppressed H3K27Me3 and effectively reactivated polycomb repressor complex 2 (PRC2)‐silenced tumor suppressor genes. Moreover, the novel inhibitors significantly suppressed tumor growth in an EZH2‐dependent manner, and tumors bearing a non‐GNA‐interacting C668S‐EZH2 mutation exhibited resistance to the inhibitors. Together, our results identify the inhibition of the signaling pathway that governs GNA‐mediated destruction of EZH2 as a promising anti‐cancer strategy

Contribution of alternative splicing to breast cancer metastasis

Alternative splicing is a major contributor to transcriptome and proteome diversity in eukaryotes. Comparing to normal samples, about 30% more alternative splicing events were recently identified in 32 cancer types included in The Cancer Genome Atlas database. Some alternative splicing isoforms and their encoded proteins contribute to specific cancer hallmarks. In this review, we will discuss recent progress regarding the contributions of alternative splicing to breast cancer metastasis. We plan to dissect the role of MTDH, CD44 and their interaction with other mRNA splicing factors. We believe an in-depth understanding of the mechanism underlying the contribution of splicing to breast cancer metastasis will provide novel strategies to the management of breast cancer