Citations

Background: Hydrogen peroxide (H2O2)-induced oxidative stress has been demonstrated to induce afterdepolarizations and triggered activities in isolated myocytes, but the underlying mechanisms remain not fully understood. We aimed to explore whether protein kinase C (PKC) activation plays an important role in oxidative stress-induced afterdepolarizations. Methods: Action potentials and ion currents of isolated rabbit cardiomyocytes were recorded using the patch clamp technique. H2O2 (1 mM) was perfused to induce oxidative stress and the specific classical PKC inhibitor, Gö 6983 (1 μM), was applied to test the involvement of PKC. Results: H2O2 perfusion prolonged the action potential duration and induced afterdepolarizations. Pretreatment with Gö 6983 prevented the emergence of H2O2-induced afterdepolarizations. Additional application of Gö 6983 with H2O2 effectively suppressed H2O2-induced afterdepolarizations. H2O2 increased the late sodium current (INa,L) (n = 7, p < 0.01) and the L-type calcium current (ICa,L) (n = 5, p < 0.01), which were significantly reversed by Gö 6983 (p < 0.01). H2O2 also increased the transient outward potassium current (Ito) (n = 6, p < 0.05). However, Gö 6983 showed little effect on H2O2-induced enhancement of Ito. Conclusions: H2O2 induced afterdepolarizations via the activation of PKC and the enhancement of ICa,L and INa,L. These results provide evidence of a link between oxidative stress, PKC activation and afterdepolarizations.

152 Background: Plasma cfDNA ARcopy number variations (CNV) have been suggested to have prognostic significance in mCRPC stage. We compared plasma AR amplification ( ARamp) with CTC counts (the only FDA approved prognostic marker in mCRPC stage) in a prospective trial of patients (pts) progressing on androgen deprivation therapy. Methods: Plasma and CTC counts were obtained concurrently as part of a prospective clinical trial in mCRPC stage pts initiating abiraterone acetate (NCT# 01953640). Plasma cfDNA was purified using DNA Blood Mini Kit (Qiagen, Valencia, CA) and AR CNVs were detected using QuantStudio3D digital PCR system (Life Technologies, Carlsbad, CA, USA). CTC enumeration was performed using the FDA cleared CellSearch platform. The distributions of overall survival (OS) time based on ARamp status and CTC counts ( < 5 vs ≥ 5 cells) were estimated using the Kaplan-Meier method. Log-rank tests were used to test association of ARamp status and CTC counts with overall survival (OS). Univariate and multivariate logistic regression models and ROC evaluated association of OS at 24 months by ARamp status and CTCs ≥ 5. Results: Between 05/2013 and 09/2015, 92 pts were enrolled of which complete CTC, plasma and outcome data was available for 70 pts. Median age of the cohort (range) was 72 yrs (39-91); Median PSA–16.2 ng/ml (range: 0.9-2026.0); Median CTC count was 2.0 (range: 0-372); 58/70 pts had bone metastases; 38/70 had high volume and 32/70 had low volume metastatic disease at the time of sample collection. The median (range) follow up time at the time of this analysis was: 26.5 (7.9-37.0) months at which time 28/70 patients had died. ARamp was present in 19/70 pts while 51/70 did not have amplification. 24/70 had CTCs ≥ 5. A significant association of increased ARamp status with OS (p < 0.0001, log-rank test; AUC: 0.66) as well as with CTC counts ≥ 5 (p = 0.001, log-rank test; AUC: 0.67) was observed. Combining CTC status and plasma ARamp status the AUC was 0.75. Conclusions: Plasma cfDNA ARamp status and CTC counts have comparable and clinically meaningful prognostic marker value in mCRPC stage patients.

Abstract Purpose: Recent progress in understanding the molecular biology of epithelial ovarian cancer has not yet translated into individualized treatment for these women or improvements in their disease outcome. Gene expression has been utilized to identify distinct molecular subtypes, but there have been no reports investigating whether or not molecular subtyping is predictive of response to bevacizumab in ovarian cancer. Experimental Design: DASL gene expression arrays were performed on FFPE tissue from patients enrolled on the ICON7 trial. Patients were stratified into four TCGA molecular subtypes. Associations between molecular subtype and the efficacy of randomly assigned therapy with bevacizumab were assessed. Results: Molecular subtypes were assigned as follows: 122 immunoreactive (34%), 96 proliferative (27%), 73 differentiated (20%), and 68 mesenchymal (19%). In univariate analysis patients with tumors of proliferative subtype obtained the greatest benefit from bevacizumab with a median PFS improvement of 10.1 months [HR, 0.55 (95% CI, 0.34–0.90), P = 0.016]. For the mesenchymal subtype, bevacizumab conferred a nonsignificant improvement in PFS of 8.2 months [HR 0.78 (95% CI, 0.44–1.40), P = 0.41]. Bevacizumab conferred modest improvements in PFS for patients with immunoreactive subtype (3.8 months; P = 0.08) or differentiated subtype (3.7 months; P = 0.61). Multivariate analysis demonstrated significant PFS improvement in proliferative subtype patients only [HR, 0.45 (95% CI, 0.27–0.74), P = 0.0015]. Conclusions: Ovarian carcinoma molecular subtypes with the poorest survival (proliferative and mesenchymal) derive a comparably greater benefit from treatment that includes bevacizumab. Validation of our findings in an independent cohort could enable the use of bevacizumab for those patients most likely to benefit, thereby reducing side effects and healthcare cost. Clin Cancer Res; 23(14); 3794–801. ©2017 AACR.

Prohibitin 1 (PHB1) is best known as a mitochondrial chaperone, and its role in cancer is conflicting. Mice lacking methionine adenosyltransferase α1 (MATα1) have lower PHB1 expression, and we reported that c‐MYC interacts directly with both proteins. Furthermore, c‐MYC and MATα1 exert opposing effects on liver cancer growth, prompting us to examine the interplay between PHB1, MATα1, and c‐MYC and PHB1's role in liver tumorigenesis. We found that PHB1 is highly expressed in normal hepatocytes and bile duct epithelial cells and down‐regulated in most human hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA). In HCC and CCA cells, PHB1 expression correlates inversely with growth. PHB1 and MAT1A positively regulate each other's expression, whereas PHB1 negatively regulates the expression of c‐MYC, MAFG, and c‐MAF. Both PHB1 and MATα1 heterodimerize with MAX, bind to the E‐box element, and repress E‐box promoter activity. PHB1 promoter contains a repressive E‐box element and is occupied mainly by MAX, MNT, and MATα1 in nonmalignant cholangiocytes and noncancerous tissues that switched to c‐MYC, c‐MAF, and MAFG in cancer cells and human HCC/CCA. All 8‐month‐old liver‐specific Phb1 knockout mice developed HCC, and one developed CCA. Five‐month‐old Phb1 heterozygotes, but not Phb1 flox mice, developed aberrant bile duct proliferation; and one developed CCA 3.5 months after left and median bile duct ligation. Phb1 heterozygotes had a more profound fall in the expression of glutathione synthetic enzymes and higher hepatic oxidative stress following left and median bile duct ligation. Conclusion: We have identified that PHB1, down‐regulated in most human HCC and CCA, heterodimerizes with MAX to repress the E‐box and positively regulates MAT1A while suppressing c‐MYC, MAFG, and c‐MAF expression; in mice, reduced PHB1 expression predisposes to the development of cholestasis‐induced CCA. (Hepatology 2017;65:1249‐1266).

Key Points The expression level of ROR1 on CLL cells varies between patients. High-level CLL-cell expression of ROR1 associates with more aggressive disease.

Abstract The Cullin 3-based E3 ubiquitin ligase substrate-binding protein SPOP is inactivated in approximately 8-15% of human prostate cancers due to gene mutation. Intriguingly, SPOP mutations and inactivation of the PTEN tumor suppressor in human prostate cancers are mutually exclusive. However, it is unclear whether SPOP remains functionally active in PTEN-deficient prostate cancer cells. In the current study, we demonstrate that PTEN loss induces phosphorylation and nuclear exportation of SPOP. We identify a putative cyclin-dependent kinase (CDK) phosphorylation site (serine 222) in SPOP BTB domain, a motif interacting with Cullin 3 and demonstrate that PTEN loss induces SPOP cytoplasm accumulation in a manner dependent on CDK2-mediated phosphorylation of SPOP at serine 222. We further show that serine 222 phosphorylation impairs dimerization and the E3 ligase activity of SPOP without affecting its interaction with Cullin 3. We also identify a potential p300 acetylation site in the C-terminal nuclear localization sequence of SPOP. We demonstrate that acetylation by p300 promotes SPOP translocation from nucleus to cytoplasm and this effect is enhanced by CDK2-mediated phosphorylation of SPOP at serine 222. In contrast, Sirt 2 and Sirt 6 of the sirtuin family are verified to be responsible for deacetylation of SPOP. In the conditional Pten knockout prostate cancer mouse model, Pten deletion induces cytosolic accumulation of SPOP, but the process is reversed in Pten and p300 double knockout prostatic cells. Collectively, our findings reveal cytoplasmic localization and enzymatic inactivation of SPOP as a previously uncharacterized mechanism that contributes to PTEN loss-induced prostate tumorigenesis. They also suggest that blocking SPOP cytoplasm localization represents a viable therapeutic option for treatment of prostate cancers harboring PTEN inactivation. Citation Format: Jian An, Haojie Huang. PTEN loss promotes phosphorylation-dependent acetylation and inhibition of SPOP tumor suppressor. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr LB-A25.

Abstract Identifying genetic variants with pleiotropic associations can uncover common pathways influencing multiple cancers. We took a two-stage approach to conduct genome-wide association studies for lung, ovary, breast, prostate, and colorectal cancer from the GAME-ON/GECCO Network (61,851 cases, 61,820 controls) to identify pleiotropic loci. Findings were replicated in independent association studies (55,789 cases, 330,490 controls). We identified a novel pleiotropic association at 1q22 involving breast and lung squamous cell carcinoma, with eQTL analysis showing an association with ADAM15/THBS3 gene expression in lung. We also identified a known breast cancer locus CASP8/ALS2CR12 associated with prostate cancer, a known cancer locus at CDKN2B-AS1 with different variants associated with lung adenocarcinoma and prostate cancer, and confirmed the associations of a breast BRCA2 locus with lung and serous ovarian cancer. This is the largest study to date examining pleiotropy across multiple cancer-associated loci, identifying common mechanisms of cancer development and progression. Cancer Res; 76(17); 5103–14. ©2016 AACR.

Key Points HERC4 is the first identified ubiquitin ligase that mediates c-Maf ubiquitination and degradation. HERC4 suppresses MM cell proliferation and delays MM tumor growth.