Role of the unique N-terminal domain of CtBP2 in determining the subcellular localisation of CtBP family proteins

BACKGROUND: CtBP1 and CtBP2 are transcriptional co-repressors that modulate the activity of a large number of transcriptional repressors via the recruitment of chromatin modifiers. Many CtBP-regulated proteins are involved in pathways associated with tumorigenesis, including TGF-beta and Wnt signalling pathways and cell cycle regulators such as RB/p130 and HDM2, as well as adenovirus E1A. CtBP1 and CtBP2 are highly similar proteins, although evidence is emerging that their activity can be differentially regulated, particularly through the control of their subcellular localisation. CtBP2s from diverse species contain a unique N-terminus, absent in CtBP1 that plays a key role in controlling the nuclear-cytoplasmic distribution of the protein.RESULTS: Here we show that amino acids (a.a.) 4-14 of CtBP2 direct CtBP2 into an almost exclusively nuclear distribution in cell lines of diverse origins. Whilst this sequence contains similarity to known nuclear localisation motifs, it cannot drive nuclear localisation of a heterologous protein, but rather has been shown to function as a p300 acetyltransferase-dependent nuclear retention sequence. Here we define the region of CtBP2 required to co-operate with a.a. 4-14 to promote CtBP2 nuclear accumulation as being within a.a. 1-119. In addition, we show that a.a. 120-445 of CtBP2 can also promote CtBP2 nuclear accumulation, independently of a.a. 4-14. Finally, CtBP1 and CtBP2 can form heterodimers, and we show that the interaction with CtBP2 is one mechanism whereby CtBP1 can be recruited to the nucleus.CONCLUSION: Together, these findings represent key distinctions in the regulation of the functions of CtBP family members that may have important implications as to their roles in development, and cell differentiation and survival.<br/

Investigation of a novel protein : protein interaction involving the hdm2 oncoprotein

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Cytoreductive surgery and intraperitoneal chemotherapy for colorectal peritoneal metastases

AIM: To systematically review the available evidence regarding cytoreductive surgery (CRS) and intraperitoneal chemotherapy (IPC) for colorectal peritoneal metastases (CPM).METHODS: An electronic literature search was carried out to identify publications reporting oncological outcome data (overall survival and/or disease free survival and/or recurrence rates) following CRS and IPC for treatment of CPM. Studies reporting outcomes following CRS and IPC for cancer subtypes other than colorectal were only included if data were reported independently for colorectal cancer-associated cases; in addition studies reporting outcomes for peritoneal carcinomatosis of appendiceal origin were excluded.RESULTS: Twenty seven studies, published between 1999 and 2013 with a combined population of 2838 patients met the predefined inclusion criteria. Included studies comprised 21 case series, 5 case-control studies and 1 randomised controlled trial. Four studies provided comparative oncological outcome data for patients undergoing CRS in combination with IPC vs systemic chemotherapy alone. The primary indication for treatment was CPM in 96% of cases (2714/2838) and recurrent CPM (rCPM) in the remaining 4% (124/2838). In the majority of included studies (20/27) CRS was combined with hyperthermic intraperitoneal chemotherapy (HIPEC). In 3 studies HIPEC was used in combination with early post-operative intraperitoneal chemotherapy (EPIC), and 2 studies used EPIC only, following CRS. Two studies evaluated comparative outcomes with CRS + HIPEC vs CRS + EPIC for treatment of CPM. The delivery of IPC was performed using an “open” or “closed” abdomen approach in the included studies.CONCLUSION: The available evidence presented in this review indicates that enhanced survival times can be achieved for CPM after combined treatment with CRS and IPC.Core tip: Colorectal cancer peritoneal metastases (CPM) confer a dismal prognosis and traditional treatment involving systemic chemotherapy, with or without palliative surgery has poor outcomes. Cytoreductive surgery (CRS) combined with intraperitoneal chemotherapy (IPC) is now advocated for selected patients with CPM. The present study provides a comprehensive summary of the available evidence relating to CRS in combination with IPC in the setting of CPM, focusing on techniques, oncological outcomes, and complications

Hdm2 recruits a hypoxia-sensitive corepressor to negatively regulate p53-dependent transcription

The transcription factor p53 lies at the center of a protein network that controls cell cycle progression and commitment to apoptosis. p53 is inactive in proliferating cells, largely because of negative regulation by the Hdm2/Mdm2 oncoprotein, with which it physically associates. Release from this negative regulation is sufficient to activate p53 and can be triggered in cells by multiple stimuli through diverse pathways. This diversity is achieved in part because Hdm2 uses multiple mechanisms to inactivate p53; it targets p53 for ubiquitination and degradation by the proteosome, shuttles it out of the nucleus and into the cytoplasm, prevents its interaction with transcriptional coactivators, and contains an intrinsic transcriptional repressor activity. Here we show that Hdm2 can also repress p53 activity through the recruitment of a known transcriptional corepressor, hCtBP2. This interaction, and consequent repression of p53-dependent transcription, is relieved under hypoxia or hypoxia-mimicking conditions that are known to increase levels of intracellular NADH. CtBP proteins can undergo an NADH-induced conformational change, which we show here results in a loss of their Hdm2 binding ability. This pathway represents a novel mechanism whereby p53 activity can be induced by cellular stress.<br/

Molecular profiling of the invasive tumor microenvironment in a 3-dimensional model of colorectal cancer cells and ex vivo fibroblasts

Invading colorectal cancer (CRC) cells have acquired the capacity to break free from their sister cells, infiltrate the stroma, and remodel the extracellular matrix (ECM). Characterizing the biology of this phenotypically distinct group of cells could substantially improve our understanding of early events during the metastatic cascade.Tumor invasion is a dynamic process facilitated by bidirectional interactions between malignant epithelium and the cancer associated stroma. In order to examine cell-specific responses at the tumor stroma-interface we have combined organotypic co-culture and laser micro-dissection techniques.Organotypic models, in which key stromal constituents such as fibroblasts are 3-dimensionally co-cultured with cancer epithelial cells, are highly manipulatable experimental tools which enable invasion and cancer-stroma interactions to be studied in near-physiological conditions.Laser microdissection (LMD) is a technique which entails the surgical dissection and extraction of the various strata within tumor tissue, with micron level precision.By combining these techniques with genomic, transcriptomic and epigenetic profiling we aim to develop a deeper understanding of the molecular characteristics of invading tumor cells and surrounding stromal tissue, and in doing so potentially reveal novel biomarkers and opportunities for drug development in CRC

Empty pelvis syndrome: a systematic review of reconstruction techniques and their associated complications

Aim: Empty pelvis syndrome is a major contributor to morbidity following pelvic exenteration. Several techniques for filling the pelvis have been proposed; however, there is no consensus on the best approach. We evaluated and compared the complications associated with each reconstruction technique with the aim of determining which is associated with the lowest incidence of complications related to the empty pelvis. Method: The systematic review protocol was prospectively registered with PROSPERO (CRD42021239307). PRISMA-P guidelines were used to present the literature. PubMed and MEDLINE were systematically searched up to 1 February 2021. A dataset containing predetermined primary and secondary outcomes was extracted. Results: Eighteen studies fulfilled our criteria; these included 375 patients with mainly rectal and gynaecological cancer. Only three studies had a follow-up greater than 2 years. Six surgical interventions were identified. Mesh reconstruction and breast prosthesis were associated with low rates of small bowel obstruction (SBO), entero-cutaneous fistulas and perineal hernia. Findings for myocutaneous flaps were similar; however, they were associated with high rates of perineal wound complications. Omentoplasty was found to have a high perineal wound infection rate (40%). Obstetric balloons were found to have the highest rates of perineal wound dehiscence and SBO. Silicone expanders effectively kept small bowel out of the pelvis, although rates of pelvic collections remained high (20%). Conclusion: The morbidity associated with an empty pelvis remains considerable. Given the low quality of the evidence with small patient numbers, strong conclusions in favour of a certain technique and comparison of these interventions remains challenging

Short- and long-term outcomes after laparoscopic and open hepatic resection: systematic review and meta-analysis

BACKGROUND: Laparoscopic liver resection (LLR) is now considered a feasible alternative to open liver resection (OLR) in selected patients. Nevertheless studies comparing LLR and OLR are few and concerns remain about long-term oncological equivalence. The present study compares outcomes with LLR vs. OLR using meta-analytical methods.METHODS: Electronic literature searches were conducted to identify studies comparing LLR and OLR. Short-term outcomes evaluated included operating time, blood loss, length of hospital stay, peri-operative morbidity and resection margin status. Longer-term outcomes included local and distant recurrence, and overall (OS) and disease-free survival (DFS). Meta-analyses were performed using the Mantel-Haenszel method and Cohen's d method, with results expressed as odds ratio (OR) or standardized mean difference (SMD), respectively, with 95% confidence intervals (CI).RESULTS: Twenty-six studies met the inclusion criteria with a population of 1678 patients. LLR resulted in longer operating time, but reduced blood loss, portal clamp time, overall and liver-specific complications, ileus and length of stay. No difference was found between LLR and OLR for oncological outcomes.DISCUSSION: LLR has short-term advantages and seemingly equivalent long-term outcomes and can be considered a feasible alternative to open surgery in experienced hands