Tetsushi Tsuruga

Identification of DBC1 as a transcriptional repressor for BRCA1

Background:DBC1/KIAA1967 (deleted in breast cancer 1) is a putative tumour-suppressor gene cloned from a heterozygously deleted region in breast cancer specimens. Caspase-dependent processing of DBC1 promotes apoptosis, and depletion of endogenous DBC1 negatively regulates p53-dependent apoptosis through its specific inhibition of SIRT1. Hereditary breast and ovarian cancer susceptibility gene product BRCA1, by binding to the promoter region of SIRT1, is a positive regulator of SIRT1 expression.Methods:A physical interaction between DBC1 and BRCA1 was investigated both in vivo and in vitro. To determine the pathophysiological significance of DBC1, its role as a transcriptional factor was studied.Results:We found a physical interaction between the amino terminus of DBC1 and the carboxyl terminus of BRCA1, also known as the BRCT domain. Endogenous DBC1 and BRCA1 form a complex in the nucleus of intact cells, which is exported to the cytoplasm during ultraviolet-induced apoptosis. We also showed that the expression of DBC1 represses the transcriptional activation function of BRCT by a transient expression assay. The expression of DBC1 also inhibits the transactivation of the SIRT1 promoter mediated by full-length BRCA1.Conclusion:These results revealed that DBC1 may modulate the cellular functions of BRCA1 and have important implications in the understanding of carcinogenesis in breast tissue.

Human homolog of Drosophila tumor suppressor Scribble negatively regulates cell-cycle progression from G1 to S phase by localizing at the basolateral membrane in epithelial cells

Drosophila tumor suppressor Scribble has been identified as an apical‐basolateral polarity determinant in epithelia. A human homolog of Drosophila Scribble, human Scribble (hScrib), has been identified as a protein targeted by human papillomavirus E6 for the ubiquitin‐mediated degradation dependent on E6AP, a cellular ubiquitin‐protein ligase. Human Scribble is classified as a LAP protein, having leucine‐rich repeats (LRRs) and PDZ domains. We investigated whether hScrib, which is thought to have a role in polarity determination based on the data of its Drosophila homolog, is involved in cell‐cycle regulation and proliferation control of epithelia. Transfection of hScrib inhibits cell‐cycle progression from G1 to S phase, and it up‐ and down‐regulates expression of adenomatous polyposis coli and cyclins A and D1, respectively. Knockdown of hScrib expression by siRNA leads to cell‐cycle progression from G1 to S phase. We explored functional domain mapping to reveal which domains of hScrib are critical for its cellular proliferation control and localization at the basolateral membrane. We found that LRRs and PDZ domain 1 are indispensable for hScrib to inhibit cell growth by blocking cell‐cycle progression and to keep its proper localization. These data indicate that basolateral membrane localization of hScrib is closely related to its proliferation control. Our findings suggest the possibility that hScrib is involved in signal transduction to negatively regulate cell proliferation by localizing at the basolateral membrane of epithelial cells through LRRs and PDZ domains. (Cancer Sci 2006; 97: 1217–1225)

Loss of Hugl-1 expression associates with lymph node metastasis in endometrial cancer

Mutation of neoplastic tumor suppressor genes, scribble, discs large, and lethal giant larvae (lgl), causes disruption of cell polarity and overproliferation of Drosophila epithelial cells and neuroblasts. Reduced expression of human homologue of lgl, Hugl-1, has been reported to be involved in development and progression of human colon cancer and malignant melanoma. To explore the association between Hugl-1 expression and clinical character in endometrial cancer, we examined the expression of Hugl-1 in primary endometrial cancer tissues. The expression of Hugl-1 mRNA in 86 primary endometrial cancer tissues was examined using semiquantitative reverse transcription polymerase chain reaction (RT-PCR). All samples were categorized into two groups: Hugl-1 positive and Hugl-1 negative. Clinical data of each group were analyzed by Fishers exact probability test and survival rates of each group were compared by Kaplan-Meier method and Log-rank test. Loss of Hugl-1 expression had correlation with the higher incidence of lymph node metastasis, but not to the patients age at onset, distant metastasis, clinical stage, lymph or venous vessel invasion, or histopathological grade of differentiation. The Hugl-1-positive group had poorer prognosis compared with the Hugl-1-negative group. These results indicate that loss of Hugl-1 expression in endometrial cancer may contribute to lymph node metastasis and it can be a factor of poor prognosis.

Multifunctional transcription factor TFII-I is an activator of BRCA1 function

Background:The TFII-I is a multifunctional transcriptional factor known to bind specifically to several DNA sequence elements and to mediate growth factor signalling. A microdeletion at the chromosomal location 7q11.23 encoding TFII-I and the related family of transcription factors may result in the onset of Williams–Beuren syndrome, an autosomal dominant genetic disorder characterised by a unique cognitive profile, diabetes, hypertension, anxiety, and craniofacial defects. Hereditary breast and ovarian cancer susceptibility gene product BRCA1 has been shown to serve as a positive regulator of SIRT1 expression by binding to the promoter region of SIRT1, but cross talk between BRCA1 and TFII-I has not been investigated to date.Methods:A physical interaction between TFII-I and BRCA1 was explored. To determine pathophysiological function of TFII-I, its role as a transcriptional cofactor for BRCA1 was investigated.Results:We found a physical interaction between the carboxyl terminus of TFII-I and the carboxyl terminus of BRCA1, also known as the BRCT domain. Endogenous TFII-I and BRCA1 form a complex in nuclei of intact cells and formation of irradiation-induced nuclear foci was observed. We also showed that the expression of TFII-I stimulates the transcriptional activation function of BRCT by a transient expression assay. The expression of TFII-I also enhanced the transcriptional activation of the SIRT1 promoter mediated by full-length BRCA1.Conclusion:These results revealed the intrinsic mechanism that TFII-I may modulate the cellular functions of BRCA1, and provide important implications to understand the development of breast cancer.

Minimization of curative surgery for treatment of early cervical cancer: a review

Surgery is effective and useful for curative treatment of patients with early invasive cervical cancer, yet minimization of surgical procedures provides many additional advantages for patients. Because the mean age of patients diagnosed with cervical precancer and invasive cancer has been decreasing, the need for minimization of surgery to reduce disruption of fertility is increasing. Trachelectomy is an innovative procedure for young patients with invasive cancer. Minimally invasive procedures are increasingly implemented in the treatment of patients with early cervical cancer, such as laparoscopic/robotic surgery and sentinel lymph node navigation. The use of modified radical hysterectomy may not only be curative but also minimally invasive for Stage IA2-IB1 patients with a tumor size <2 cm in diameter. Here, we have summarized and discussed the minimally invasive procedures for the treatment of patients with early cervical cancer.

hScrib, a human homologue of Drosophila neoplastic tumor suppressor, is a novel death substrate targeted by caspase during the process of apoptosis

hScrib, human homologue of Drosophila neoplastic tumor suppressor, was identified as a target of human papillomavirus E6 oncoprotein for the ubiquitin‐mediated degradation. Here, we report that hScrib is a novel death substrate targeted by caspase. Full‐length hScrib was cleaved by caspase during death ligands‐induced apoptosis, which generates a p170 C‐terminal fragments in Hela cells. In vitro cleavage assay using recombinant caspases showed that hScrib is cleaved by the executioner caspases. DNA damage‐induced apoptosis caused loss of expression of full‐length hScrib, which was recovered by addition of capase‐3 inhibitor in HaCat cells. TUNEL positive apoptotic cells, which were identified 4 h after UV irradiation in HaCat cells, showed loss of hScrib expression at the adherens junction. Mutational analysis identified the caspase‐dependent cleavage site of hScrib at the position of Asp‐504. Although MDCK cells transfected with GFP‐fused wild‐type hScrib showed loss of E‐cadherin expression and shrinkage of cytoplasm by UV irradiation, cells transfected with hScrib with Ala substitution of Asp‐504 showed resistance to caspase‐dependent cleavage of hScrib and intact expression of E‐cadherin. These results indicate that caspase‐dependent cleavage of hScrib is a critical step for detachment of cell contact during the process of apoptosis.

High-risk human papillomavirus correlates with recurrence after laser ablation for treatment of patients with cervical intraepithelial neoplasia 3: A long-term follow-up retrospective study

The purpose of our study was to evaluate the efficacy of laser ablation as a conservative treatment for cervical intraepithelial neoplasia 3 (CIN3) and assess whether the human papillomavirus (HPV) test is useful to predict recurrence after treatment.

Positive peritoneal cytology at interval surgery is a poor prognostic factor in patients with stage T3c advanced ovarian carcinoma: A retrospective study.

The purpose of our study is to investigate clinically significant prognostic factors at the time of interval surgery (IS), comprising interval look surgery and interval debulking surgery, for T3c (International Federation of Gynecology and Obstetrics stage IIIc to IV) advanced ovarian cancer (AOC) patients during primary treatment.

Measurement of endometrial thickness by transvaginal ultrasonography to predict pathological response to medroxyprogesterone acetate in patients with grade 1 endometrioid adenocarcinoma

The aim of the present study was to evaluate whether measuring endometrial thickness during fertility-sparing treatment with medroxyprogesterone acetate (MPA) can be a predictive marker for effectiveness in women with endometrioid adenocarcinoma, grade 1 (EmCa, G1). A total of 32 patients with stage IA EmCa, G1 underwent treatment with MPA. Patients were <40 years of age and preferred fertility-sparing treatment. MPA (600 mg/day) with low-dose aspirin was administered orally for 26 weeks. Pathological evaluation was performed by total curettage at weeks 8 and 16 and by fractional curettage at week 26. Patients underwent curative surgery in case of disease progression. Endometrial thickness was measured by transvaginal ultrasonography at weeks 8 and 16. Patients who showed non-complete response (non-CR) had thicker endometrium than that of CR patients at weeks 8 and 16. Receiver operating characteristic analysis revealed cut-off values of 8.3 and 4.7 mm endometrial thickness at weeks 8 and 16, respectively, for non-CR. Endometrial thickness >5 mm at week 16 was an independent factor for prediction of non-CR. Measurement of endometrial thickness during MPA treatment may be useful as a predictive marker for pathological response to MPA in patients with EmCa, G1.