Viral ski inhibits retinoblastoma protein (Rb)-mediated transcriptional repression in a dominant negative fashion

The mechanism by which the viral oncogene ski (v-ski) transforms chicken embryo fibroblasts is currently unknown. Recently, the c-ski gene product (c-Ski) was found to bind to N-CoR (nuclear hormone receptor co-repressor), an element implicated in transcriptional repression mediated by multiple transcriptional repressors including the nuclear hormone receptors and Mad. c-Ski is required for transcriptional repression mediated by Mad involved in negative regulation of cellular proliferation. v-Ski abrogates Mad-induced transcriptional repression in a dominant negative fashion. Here we report that v-Ski also inhibits transcriptional repression mediated by Rb, another tumor suppressor gene product. Rb forms a complex with c-Ski, Sin3A, and histone deacetylase (HDAC) via direct binding to c-Ski and HDAC. c-Ski is required for the transcriptional repression mediated by Rb. These results suggest that inhibition of Rb activity contributes, at least partly, to transformation by v-Ski.

CBP alleviates the intramolecular inhibition of ATF-2 function

The transcription factor ATF-2 (also called CRE-BP1), whose DNA-binding domain consists of a basic amino acid cluster and a leucine zipper (b-ZIP) region, binds to the cAMP response element as a homodimer or as a heterodimer with c-Jun. The amino-terminal region of ATF-2 containing the transcriptional activation domain is phosphorylated by stress-activated kinases, which leads to activation of ATF-2. We report here that CBP, which was originally identified as a co-activator of CREB, directly binds to the b-ZIP region of ATF-2 via a Cys/His-rich region termed C/H2, and potentiates trans-activation by ATF-2. The b-ZIP region of ATF-2 was previously shown to interact with the amino-terminal region intramolecularly and to inhibit trans-activating capacity. The binding of CBP to the b-ZIP region abrogates this intramolecular interaction. The adenovirus 13S E1A protein which binds to the b-ZIP region of ATF-2 also inhibited this intramolecular interaction, suggesting that both CBP and 13S E1A share a similar function as positive regulators of ATF-2. We found that the b-ZIP regions of c-Jun and CREB also interact with the C/H2 domain of CBP, suggesting that CBP acts as a regulator for a group of b-ZIP-containing proteins. These results shed light on a novel aspect of CBP function as a regulator for a group of b-ZIP-containing proteins.

Cavo-atrial thrombectomy prior to hepatectomy for hepatocellular carcinoma with tumor thrombus in the right atrium: a case report

BACKGROUND

Hepatocellular carcinoma (HCC) with tumor thrombus (TT) in the right atrium is a critical condition. The general consensus is to perform hepatectomy prior to cavo-atrial thrombectomy because of the risk of uncontrollable bleeding during the liver transection after heparinization. However, sudden cardiac arrest due to the ball-valve effect and pulmonary embolism have been reported in cases of TT. Cavo-atrial thrombectomy prior to hepatectomy for HCC with TT in the right atrium was successfully performed to prevent sudden cardiac arrest and pulmonary embolism.

CASE PRESENTATION

Tumor thrombectomy under cardiopulmonary bypass with heparin and electrical ventricular fibrillation prior to hepatectomy was successfully performed to prevent sudden cardiac arrest or pulmonary embolism in a 75-year-old woman with a huge HCC and TT in the right atrium. After the neutralization of heparin, right hepatectomy with tumor thrombectomy in the inferior vena cava was performed. The total operation time was 9 h, and the total blood loss was 8200 mL. The patient's postoperative course was uneventful, and she was discharged 14 days after surgery. One year after surgery, she is alive with HCC recurrence in the lung.

CONCLUSIONS

Cavo-atrial thrombectomy prior to hepatectomy for HCC with TT in the right atrium can be performed safely to prevent sudden cardiac arrest and pulmonary embolism by collaboration of cardiovascular surgeons and gastroenterological surgeons.

[Two Cases of Metastatic Colorectal Cancer Treated with TAS-102 plus Bevacizumab]

Trifluridine/tipiracil (TAS-102) is an important chemotherapeutic agent recommended by the Japanese guidelines as third- or fourth-line treatment for colorectal cancer. Some studies have reported that administration of TAS-102 concomitant with bevacizumab prolongs progression-free and overall survival in colorectal cancer. We describe 2 patients treated with a chemotherapeutic regimen comprising TAS-102 concomitant with bevacizumab for recurrent colorectal cancer. No adverse events ≥Grade 3(except for hematotoxicity)were observed in these patients. The patient received several courses of chemotherapy with adjustments of the dose and dosing intervals to prevent neutropenia. Combination therapy using TAS-102 and bevacizumab is a feasible Late-line chemotherapeutic regimen for colorectal cancer.