Tatsuyuki Chiyoda

Regulation of MKL1 via actin cytoskeleton dynamics drives adipocyte differentiation

Cellular differentiation is regulated through activation and repression of defined transcription factors. A hallmark of differentiation is a pronounced change in cell shape, which is determined by dynamics of the actin cytoskeleton. Here we show that regulation of the transcriptional coactivator MKL1 (megakaryoblastic leukemia 1) by actin cytoskeleton dynamics drives adipocyte differentiation mediated by peroxisome proliferator-activated receptor γ (PPARγ), a master transcriptional regulator of adipogenesis. Induction of adipocyte differentiation results in disruption of actin stress fibres through downregulation of RhoA-ROCK signalling. The consequent rapid increase in monomeric G-actin leads to the interaction of G-actin with MKL1, which prevents nuclear translocation of MKL1 and allows expression of PPARγ followed by adipogenic differentiation. Moreover, we found that MKL1 and PPARγ act in a mutually antagonistic manner in the adipocytic differentiation programme. Our findings thus provide new mechanistic insight into the relation between the dynamics of cell shape and transcriptional regulation during cellular differentiation.

Induction of ZEB proteins by inactivation of RB protein is key determinant of mesenchymal phenotype of breast cancer.

Background: Inactivation of RB is a key event for induction of EMT in cancers. Results: ZEB proteins are markedly up-regulated through the reduction of miR-200 family of microRNAs in RB-inactive cancer cells. Conclusion: RB/ZEB pathway plays a pivotal role in mesenchymal and aggressive phenotype in breast cancers. Significance: Suppressing ZEB1 by cyclin-dependent kinase inhibitors provides a novel therapeutic strategy for RB-inactive breast cancers. We previously showed that depletion of the retinoblastoma protein (RB) induces down-regulation of the adhesion molecule E-cadherin and thereby triggers the epithelial-mesenchymal transition. To further characterize the effect of RB inactivation on the phenotype of cancer cells, we have now examined RB expression in human breast cancer cell lines and clinical specimens. We found that RB-inactive cells exhibit a mesenchymal-like morphology and are highly invasive. We also found that ZEB proteins, transcriptional repressors of the E-cadherin gene, are markedly up-regulated in these cells in a manner sensitive to the miR-200 family of microRNAs. Moreover, depletion of ZEB in RB-inactive cells suppressed cell invasiveness and proliferation and induced epithelial marker expression. These results implicate ZEB in induction of the epithelial-mesenchymal transition, as well as in maintenance of the mesenchymal phenotype in RB-inactive cells. We also developed a screening program for inhibitors of ZEB1 expression and thereby identified several cyclin-dependent kinase inhibitors that blocked both ZEB1 expression and RB phosphorylation. Together, our findings suggest that RB inactivation contributes to tumor progression not only through loss of cell cycle control but also through up-regulation of ZEB expression and induction of an invasive phenotype.

LATS1/WARTS phosphorylates MYPT1 to counteract PLK1 and regulate mammalian mitotic progression

Showing convergence with budding yeast mitotic exit network signaling, the LATS1/WARTS kinase phosphorylates the MYPT1 phosphatase to control PLK1 at the G2 DNA damage checkpoint.

Lymph node metastasis in grossly apparent stages I and II epithelial ovarian cancer

Objectives: Incidence of lymph node metastasis is relatively high even in early-stage epithelial ovarian cancers (EOC). Lymphadenectomy is important in the surgical treatment of EOC; however, the exact role of lymphadenectomy in the management of EOC remains unclear. In this study, we evaluated lymph node metastasis in stages I and II EOC patients. Patients and Methods: Seventy-nine patients with stage I/II EOC underwent initial surgery, and 68 patients received adjuvant platinum and taxane chemotherapy after surgery at Keio University Hospital. The patients were evaluated with respect to age at diagnosis, clinical stage, histology, histological grade, and tumor laterality. Results: Of the 79 patients, 10 (12.7%) had lymph node metastasis. Of these, 4 (5.1%) had lymph node metastasis in paraaortic lymph node (PAN) only, 1 (1.3%) in pelvic lymph node (PLN) only, and 5 (6.3%) in both PAN and PLN. The incidence of serous-type lymph node metastasis in PAN, PAN + PLN, and total was higher than nonserous type (25% vs 1.5%, P < 0.0001; 25% vs 3.0%, P = 0.001; 50% vs 5.9%, P < 0.0001). However, there was no significant difference between lymph node status and T factor or histological grade. In 78% of patients (7/9), metastases in contralateral lymph nodes were present (contralateral, 2; bilateral, 5). There was no significant difference in progression-free survival between node-positive and node-negative groups (P = 0.47). Conclusions: Based on diagnostic value, the result suggests that the role of lymphadenectomy might differ by histological type, as its therapeutic effect might be unclear. A multicenter analysis is essential for confirmation.

The Anaphase-Promoting Complex/Cyclosome Activator Cdh1 Modulates Rho GTPase by Targeting p190 RhoGAP for Degradation

ABSTRACT Cdh1 is an activator of the anaphase-promoting complex/cyclosome and contributes to mitotic exit and G1 maintenance by targeting cell cycle proteins for degradation. However, Cdh1 is expressed and active in postmitotic or quiescent cells, suggesting that it has functions other than cell cycle control. Here, we found that homozygous Cdh1 gene-trapped (Cdh1GT/GT) mouse embryonic fibroblasts (MEFs) and Cdh1-depleted HeLa cells reduced stress fiber formation significantly. The GTP-bound active Rho protein was apparently decreased in the Cdh1-depleted cells. The p190 protein, a major GTPase-activating protein for Rho, accumulated both in Cdh1GT/GT MEFs and in Cdh1-knockdown HeLa cells. Cdh1 formed a physical complex with p190 and stimulated the efficient ubiquitination of p190, both in in vitro and in vivo. The motility of Cdh1-depleted HeLa cells was impaired; however, codepletion of p190 rescued the migration activity of these cells. Moreover, Cdh1GT/GT embryos exhibited phenotypes similar to those observed for Rho-associated kinase I and II knockout mice: eyelid closure delay and disruptive architecture with frequent thrombus formation in the placental labyrinth layer, respectively. Furthermore, the p190 protein accumulated in the Cdh1GT/GT embryonic tissues. Our data revealed a novel function for Cdh1 as a regulator of Rho and provided insights into the role of Cdh1 in cell cytoskeleton organization and cell motility.

Overexpression of cofilin 1 can predict progression-free survival in patients with epithelial ovarian cancer receiving standard therapy.

The aim of this study was to examine the relation between cofilin 1 expression and progression-free survival in advanced epithelial ovarian cancer. We performed quantitative reverse transcriptase polymerase chain reaction and immunohistochemical analysis in 78 patients with advanced epithelial ovarian cancer (excluding those with mucinous and clear-cell types). All patients received the standard therapy, including staging laparotomy and adjuvant chemotherapy consisting of carboplatin and paclitaxel. Of 78 samples, RNA from 62 samples was available for reverse transcriptase polymerase chain reaction analysis. We defined cofilin 1 high expression as relative gene expression equal to or higher than the median and low expression as gene expression lower than median. The progression-free survival was longer in cofilin 1 low-expression cases than in high-expression cases (P = .039). Multivariate analysis demonstrated that stage and cofilin 1 expression were significant predictors of progression-free survival. Of the 78 samples, 54 were appropriate for immunohistochemical study. In 35 of those 54 cases, cofilin 1 protein expression was detected. The progression-free survival was longer in cofilin 1 protein-negative cases than in protein-positive cases (P = .042). Expression of cofilin 1 may predict the progression-free survival of patients with advanced epithelial ovarian cancer receiving standard therapy.

IGF2 Preserves Osteosarcoma Cell Survival by Creating an Autophagic State of Dormancy That Protects Cells against Chemotherapeutic Stress

Osteosarcoma is a malignant bone tumor in children and adolescents characterized by intrinsic therapeutic resistance. The IGF2 is expressed at elevated levels in osteosarcoma after treatment with chemotherapy, prompting an examination of its functional contributions to resistance. We found that continuous exposure to IGF2 or insulin in the absence of serum created a dormant growth state in osteosarcoma cells that conferred resistance to various chemotherapeutic drugs in vitro. Mechanistic investigations revealed that this dormant state correlated with downregulation of downstream signaling by the IGF1 receptor, heightened cell survival, enhanced autophagy, and the presence of extracellular glutamine. Notably, inhibiting autophagy or depleting glutamine was sufficient to increase chemotherapeutic sensitivity in osteosarcoma xenografts in mice. Clinically, we confirmed that IGF expression levels were elevated in human osteosarcoma specimens from patients who received chemotherapy. Together, our results suggest that activation of IGF or insulin signaling preserves the survival of osteosarcoma cells under chemotherapeutic stress, providing a drug-resistant population that may engender minimal residual disease. Attenuating this survival mechanism may help overcome therapeutic resistance in osteosarcoma.

Expression profiles of carcinosarcoma of the uterine corpus—are these similar to carcinoma or sarcoma?

Uterine carcinosarcoma (CS) is usually classified as uterine endometrial carcinoma (EC). However, CS is more aggressive even compared with high grade EC. CS is also reported to undergo epithelial to mesenchymal transition (EMT). In this study, we compared the gene expression profiles of CS, EC, and uterine sarcoma (US) and evaluated the role of EMT and chromosomal aberrations in CS tumor formation. Frozen tissues of 46 patients (14 CS, 24 EC, and 8 US) were included. The similarity was examined by Gene Set Enrichment Analysis (GSEA), Fishers exact test, and clustering using “intrinsic gene set”. We examined the expression of 39 EMT‐related genes and evaluated TGF‐beta signaling by phospho‐SMAD2/3 (p‐SMAD2/3) staining. Chromosomal regions differing between CS and EC were identified by chromosomal GSEA and comparative genomic hybridization (CGH) microarrays. Three statistical methods confirmed that CS resembled US rather than EC. Acquired markers of EMT were upregulated and attenuated markers of EMT were downregulated in CS. Immunohistochemistry showed that carcinomatous region of CS have higher expression of p‐SMAD2/3 than EC (P = 0.008). Chromosomal GSEA showed that genes located at 19q13 had higher expression in CS. Furthermore, CGH microarray indicated that the TGFB1 locus at 19q13.1 was amplified in 4 of 7 samples. Based on the expression profile, CS resembles US rather than EC. TGF‐beta signaling is activated in CS and chromosomal gains at 19q13, which includes the TGFB1 locus, suggest that this may contribute to high expression of TGF‐beta and thereby EMT phenotype of CS.

EGRI and FOSB gene expressions in cancer stroma are independent prognostic indicators for epithelial ovarian cancer receiving standard therapy

Stromal components interact with cancer cells to promote growth and metastasis. The purpose of this study was to identify genes expressed in stroma, which could provide prognostic information in epithelial ovarian cancer (EOC). Seventy‐four patients were included. We performed gene expression profiling and confirmed array data using RT‐PCR and immunohistochemistry. By microarray analysis, 52 candidate genes associated with progression free survival (PFS) were identified (P < 0.005). Expression of the early growth response 1 (EGR1) and FBJ murine osteosarcoma viral oncogene homolog B (FOSB) genes was further analyzed. Array data were confirmed by RT‐PCR and multivariate analysis demonstrated that both EGR1 and FOSB expression in cancer stroma, and EGR1 expression in cancer are independent prognostic factors in EOC. Immunohistochemically, EGR1 protein is localized in cancer cells and α‐smooth muscle actin positive stromal fibroblasts. The EGR1 and FOSB expression in stromal cells and EGR1 expression in cancer cells are prognostic indicators in EOC.

Role of circulating free alu DNA in endometrial cancer.

Conclusions Measurement of cell-free DNA is not useful for EC screening; however, the change of cell-free DNA in a patient may be a prognostic biomarker of EC.