Hugh Colvin

Gastroenterological surgery in Japan: The past, the present and the future

In the last two centuries, there has been remarkable progress in the field of gastroenterological surgery, including the curative resection of cancers, replacement of failed organs through transplantation, increased safety of undergoing major surgeries and decreased operative morbidity through developments in minimal access surgery. Japan has very much been at the forefront of these advances, as is evident from the present review, from advancing the surgical management of gastric cancer to the pioneering work in live‐donor transplantation. This review also highlights many instances where surgical management of the same pathologies has evolved differently between Japan and the West. It is encouraging that many procedures established in Japan are eventually taken up by the West, often after rigorous assessment affirming the quality and applicability of such techniques. In Japan, many of the crucial issues in gastroenterological surgery are increasingly addressed through large multi‐institutional prospective control trials, ensuring that Japanese surgeons continue to contribute to the advances in gastroenterological surgery.

Tumour-suppressive function of SIRT4 in human colorectal cancer.

Background:SIRT4, which is localised in the mitochondria, is one of the least characterised members of the sirtuin family of nicotinamide adenine dinucleotide-dependent enzymes that play key roles in multiple cellular processes such as metabolism, stress response and longevity. There are only a few studies that have characterised its function and assessed its clinical significance in human cancers.Methods:We established colorectal cancer cell lines (SW480, HCT116, and HT29) overexpressing SIRT4 and investigated their effects on proliferation, migration and invasion, as well as E-cadherin expression, that negatively regulates tumour invasion and metastases. The associations between SIRT4 expression in colorectal cancer specimens and clinicopathological features including prognosis were assessed by immunohistochemistry.Results:SIRT4 upregulated E-cadherin expression and suppressed proliferation, migration and invasion through inhibition of glutamine metabolism in colorectal cancer cells. Moreover, SIRT4 expression in colorectal cancer decreased with the progression of invasion and metastasis, and a low expression level of SIRT4 was correlated with a worse prognosis.Conclusions:SIRT4 has a tumour-suppressive function and may serve as a novel therapeutic target in colorectal cancer.

Oncometabolite D-2-Hydroxyglurate Directly Induces Epithelial-Mesenchymal Transition and is Associated with Distant Metastasis in Colorectal Cancer

Deranged metabolism is a hallmark of cancer, playing a significant role in driving the disease process. One such example is the induction of carcinogenesis by the oncometabolite D-2 hydroxyglutarate (D-2HG), which is produced by the mutated enzyme isocitrate dehydrogenase (IDH) occurring in subsets of leukaemias and brain tumours. The oncogenic property of D-2HG appears to stem from its ability to interfere with the activities of α-ketoglutarate-dependent dioxygenases, including the Jumonji family histone demethylases. Here, we find in colorectal cancer cells that even in the absence of IDH mutation, the levels of D-2HG and its enantiomer L-2HG were elevated through glutamine anaplerosis. D-2HG, but not L-2HG, increased the trimethylation of histone H3 lysine 4 of the promoter region of ZEB1, a master regulator of epithelial-mesenchymal transition (EMT), and increased the expression of the ZEB1 gene to directly induce EMT in colorectal cancer cells. EMT promotes the ability of cancer cells to invade the local tissue and enter into the bloodstream, leading to distant organ metastasis. D-2HG levels were elevated in colorectal cancer specimens, particularly in those associated with distant metastasis, supporting the observations in vitro and implicating the contribution of D-2HG in metastasis, the major cause of death in this disease.

Metabolic Adaptation to Nutritional Stress in Human Colorectal Cancer

Tumor cells respond to their microenvironment, which can include hypoxia and malnutrition, and adapt their metabolism to survive and grow. Some oncogenes are associated with cancer metabolism via regulation of the related enzymes or transporters. However, the importance of metabolism and precise metabolic effects of oncogenes in colorectal cancer remain unclear. We found that colorectal cancer cells survived under the condition of glucose depletion, and their resistance to such conditions depended on genomic alterations rather than on KRAS mutation alone. Metabolomic analysis demonstrated that those cells maintained tricarboxylic acid cycle activity and ATP production under such conditions. Furthermore, we identified pivotal roles of GLUD1 and SLC25A13 in nutritional stress. GLUD1 and SLC25A13 were associated with tumor aggressiveness and poorer prognosis of colorectal cancer. In conclusion, GLUD1 and SLC25A13 may serve as new targets in treating refractory colorectal cancer which survive in malnutritional microenvironments.

BRAF V600E inhibition stimulates AMP-activated protein kinase-mediated autophagy in colorectal cancer cells.

Although BRAFV600E mutation is associated with adverse clinical outcomes in patients with colorectal cancer (CRC), response and resistance mechanisms for therapeutic BRAFV600E inhibitors remains poorly understood. In the present study, we demonstrate that selective BRAFV600E inhibition activates AMP-activated protein kinase (AMPK), which induces autophagy as a mechanism of therapeutic resistance in human cancers. The present data show AMPK-dependent cytoprotective roles of autophagy under conditions of therapeutic BRAFV600E inhibition, and AMPK was negatively correlated with BRAFV600E-dependent activation of MEK-ERK-RSK signaling and positively correlated with unc-51-like kinase 1 (ULK1), a key initiator of autophagy. Furthermore, selective BRAFV600E inhibition and concomitant suppression of autophagy led to the induction of apoptosis. Taken together, present experiments indicate that AMPK plays a role in the survival of BRAFV600E CRC cells by selective inhibition and suggest that the control of autophagy contributes to overcome the chemoresistance of BRAFV600E CRC cells.

Hereditary Gastric Cancer Syndromes

Hereditary gastric cancer syndromes are a rare but distinct cause of gastric cancers. The genetic mutations underlying most affected families are unknown. Mutations of CDH1 occur in some patients affected by hereditary diffuse gastric cancer, and is the only practical marker for guiding management. Carriers of CDH1 mutations are at risk for a highly penetrant, aggressive and early-onset diffuse-type gastric cancer, and these individuals are usually offered prophylactic total gastrectomy. Further research is required to identify other genetic mutations responsible for these syndromes to improve our understanding of the underlying disease mechanisms and optimize the clinical management of affected individuals.

Mathematical analysis predicts imbalanced IDH1/2 expression associates with 2-HG-inactivating β-oxygenation pathway in colorectal cancer

Bioinformatics and computational modeling offer innovative approaches to investigate cancer metabolism and predict the secondary and tertiary cellular responses. Dysregulation of metabolism has also been implicated in the pathophysiology of cancer. A significant proportion of patients with glioblastoma and hematological malignancies harbor the mutated forms of the oxidative phosphorylation (OxPhos) enzymes, isocitrate dehydrogenase (IDH) 1 or 2. The mutated forms of IDH1 and IDH2 produce an oncogenic metabolite, D-2-hydroxyglutarate (D2HG). A recent study of breast cancer patients showed that D2HG can also be produced in the absence of mutated IDH, through an alternative route involving over-activated MYC signaling. We developed a novel methodology to computationally analyze gene expression in colorectal cancer (CRC), and identified novel sets of genes that are associated with patient survival. The study of OxPhos-related genes revealed that an imbalance between the expression of IDH1 and IDH2, defined as overexpression of one isoform in relation to the other, was associated with worse prognosis in CRC patients. This effect was further accentuated by reduced expression of the β-oxygenation enzyme, 3-D-hydroxyacyl-CoA dehydratase (HCDH) 4, which has been reported to contribute to metabolism of intracellular D2HG. The present computational analysis revealed a novel and potential mechanism of CRC development, through over-production of D2HG when there is an imbalance between IDH1 and IDH2 expression, resulting in decreased clearance of D2HG when the β-oxidization pathway is diminished. Additional validation analysis with another gene expression dataset resulted in IDH1/2 imbalanced expression with a shorter DFS compared with balanced expression. Altogether, these findings provide a strong rationale for studying this mechanism further in order to discover novel therapeutic targets for the treatment of CRC.

Getting to the heart of the matter in cancer: Novel approaches to targeting cancer stem cells

Cancer is one of the leading causes of deaths worldwide. While cancers may initially show good response to chemotherapy or radiotherapy, it is not uncommon for them to recur at a later date. This phenomenon may be explained by the existence of a small population of cancer stem cells, which are inherently resistant to anti-cancer treatment as well as being capable of self-renewal. Therefore, while most of the tumour bulk consisting of cells that are not cancer stem cells respond to treatment, the cancer stem cells remain, leading to disease recurrence. Following this logic, the effective targeting of cancer stem cells holds promise for providing long-term cure in individuals with cancer. Cancer stem cells, like normal stem cells are endowed with mechanisms to protect themselves against a wide range of insults including anti-cancer treatments, such as the enhancement of the DNA damage response and the ability to extrude drugs. It is therefore important to develop new strategies if cancer stem cells are to be eradicated. In this review, we describe the strategies that we have developed to target cancer stem cells. These strategies include the targeting of the histone demethylase jumonji, AT rich interactive domain 1B (JARID1B), which we found to be functionally significant in the maintenance of cancer stem cells. Other strategies being pursued include reprogramming of cancer stem cells and the targeting of a functional cell surface marker of liver cancer stem cells, the aminopeptidase CD13.

Colorectal cancer: Back to the stroma—the real villain in colorectal cancer?

The cells responsible for particular gene signatures in large-scale microarray studies of colorectal cancer have now been revealed. In doing so, the gene signature associated with poor prognosis is shown to be predominantly of stromal origin.

Cancer Stem Cells of the Digestive System

Stem cells of the digestive system are ideal in many ways for research, given they are abundant, highly proliferative and have a uniform structural arrangement. This in turn has enormously aided the research of cancer stem cells of the digestive system, which is now shaping our understanding of cancer stem cells. In this review, the recent advances in the understanding of cancer stem cells of the digestive system have been summarized, including aspects such as their identification, origin, cell-cycle dormancy, relationship with epithelial-mesenchymal transition, cellular metabolism and the underlying molecular mechanisms. Newly acquired knowledge concerning cancer stem cells have led to the development of novel cancer therapeutics with provisional yet encouraging results.