Soichi Tsutsumi

Inhibition of autophagy augments 5-fluorouracil chemotherapy in human colon cancer in vitro and in vivo model.

Although 5-fluorouracil (5-FU)-based adjuvant chemotherapy is widely used in the treatment of colorectal cancer, novel therapeutic strategies need to be explored. It has been reported that autophagy is extensively implicated in cancer. However, the function of autophagy is not fully understood. In the present study, apoptosis induced by 5-FU in 3 human colon cancer cell lines (HCT116, DLD-1, and DLD-1/5-FU (a specific 5-FU-resistant sub-line)) was measured using MTT assay, DNA fragmentation assay, Hoechst 33342 staining, and caspase-3 immunoblotting. The autophagy activation induced by 5-FU treatment was revealed by microtubule-associated protein 1 light chain 3 (LC3) immunofluorescence and immunoblotting and p62 immunoblotting. Inhibition of autophagy by 3-methyladenine (3-MA) or small interference RNA targeting Atg7 (Atg7 siRNA) significantly augmented 5-FU-induced apoptosis. This synergistic effect of 5-FU and 3-MA was further confirmed in the DLD-1 xenograft tumour model. Tumour growth was suppressed more significantly with combination treatment than 5-FU treatment alone. In conclusion, autophagy was activated as a protective mechanism against 5-FU-induced apoptosis and its inhibition could be a promising strategy for adjuvant chemotherapy in colon cancer.

Inhibition of Autophagy by 3-MA Enhances the Effect of 5-FU-Induced Apoptosis in Colon Cancer Cells

Background5-fluorouracil-(5-FU)-based adjuvant chemotherapy is widely used for the treatment of colorectal cancer. However, 5-FU resistance in the course of treatment has become more common. Therefore, new therapeutic strategies and/or new adjuvant drugs still need to be explored.MethodsTwo colon-cancer-derived cell lines, colon26 and HT29, were used to investigate the effect of 5-FU, 3-methyladenine (3-MA, an autophagy inhibitor), or their combination on apoptotic cell death and autophagy. MTT assay, Hochest plus propidium iodide (PI) staining, and DNA fragmentation assay were used to observe apoptosis. Meanwhile, monodansylcadaverine (MDC) was used to detect autophagy. Finally, immunoblotting assay was used to explore the molecular change that occurred.ResultsWe observed the apoptosis induced by 5-FU in colon cancer cells. Meanwhile, autophagy was also stimulated. The combination treatment of 3-MA and 5-FU significantly increased the apoptotic cell death. By isolating the subcellular fractions of mitochondria and cytosol, we observed that the release of cytochrome c was increased in combination-treated cells. Cytochrome c resulted in the activation of caspase-3, thus activating PARP. Moreover, the anti-apoptotic protein, Bcl-xL, was significantly downregulated by 3-MA.ConclusionsOur results suggest that 5-FU-induced apoptosis in colon cancer cells can be enhanced by the inhibitor of autophagy, 3-MA. Autophagy might play a role as a self-defense mechanism in 5-FU-treated colon cancer cells, and its inhibition could be a promising strategy for the adjuvant chemotherapy of colon cancer.

Implication of Galectin-3 in Wnt Signaling

Galectin-3 (gal-3), a member of the beta-galactoside-binding proteins family, was identified as a binding partner of beta-catenin. Analysis of the human gal-3 sequence reveled a structural similarity to beta-catenin as it also contains the consensus sequence (S92XXXS96) for glycogen synthase kinase-3beta (GSK-3beta) phosphorylation and can serve as its substrate. In addition, Axin, a regulator protein of Wnt that complexes with beta-catenin, also binds gal-3 using the same sequence motif identified here by a deletion mutant analysis. The data presented here give credence to the suggestion that gal-3 is a key regulator in the Wnt/beta-catenin signaling pathway and highlight the functional similarities between gal-3 and beta-catenin.

Transient gene silencing of galectin-3 suppresses pancreatic cancer cell migration and invasion through degradation of β-catenin

Pancreatic cancer is a leading cause of cancer‐related mortality and often has a poor prognosis because of its late diagnosis, aggressive local invasion, early metastasis and poor response to chemotherapy. The chemotherapeutic agent gemcitabine is effective for treating advanced pancreatic cancer, but its efficacy remains less than satisfactory. It is expected that further investigation of pancreatic cancer cell invasion and development of strategies to block this process should improve the disease prognosis. In this study, we tested our hypothesis that galectin‐3 (gal‐3), a multifunctional member of the β‐galactoside‐binding protein family, may regulate pancreatic cancer cell motility and silencing of it inhibit cell motility. Previous studies demonstrated that this protein is associated with tumor cell adhesion, proliferation, differentiation, angiogenesis, apoptosis and metastasis. Here, we used gal‐3 small interfering RNA (siRNA) to silence its expression in various pancreatic cancer cell lines to determine whether gal‐3 regulates cell proliferation, migration and invasion in vitro. We found that silencing gal‐3 reduced cellular migration and invasion, but failed to affect proliferation. In gal‐3 siRNA‐transfected cells, we detected a decrease in β‐catenin expression, an important signal for cancer cell invasion, which was caused by downregulation of phosphorylated Akt and GSK‐3β. We also found that matrix metalloproteinase (MMP)‐2 expression was reduced by gal‐3 silencing. These results indicate that gal‐3‐mediated invasion via MMP‐2 regulated by β‐catenin degradation is initiated by Akt phosphorylation in pancreatic cancer cells. Our results suggest that gal‐3 can be a novel therapeutic target in pancreatic cancer.

Autocrine Motility Factor Signaling Enhances Pancreatic Cancer Metastasis

Purpose: Autocrine motility factor (AMF)/phosphoglucose isomerase (PGI) is a ubiquitous cytosolic enzyme that plays a key role in glycolysis. AMF/PGI is also a multifunctional protein that acts in the extracellular milieu as a potent mitogen/cytokine. Increased expression of AMF/PGI and its receptor has been found in a wide spectrum of malignancies and is associated with cancer progression and metastasis. Recent studies indicated that AMF is induced by hypoxia and enhances the random motility of pancreatic cancer cells. In the present study, the role and regulation of AMF in the growth and metastasis of pancreatic cancer cells were determined. Experimental Design: In this study, we assessed whether overexpression of AMF in human pancreatic cancer cells enhances the liver metastasis using an orthotopic mouse tumor model. We also investigated the intracellular signal transduction pathways of AMF in human pancreatic cancer cell lines. Results: Overexpression of AMF stimulated in vitro invasion of MIA PaCa-2 cells. In vivo, after orthotopic implantation into the pancreas of nude mice, parental and empty vector-transfected MIA PaCa-2 cells produced locally relatively small tumors with no evidence of liver metastasis, whereas AMF-transfected MIA PaCa-2 cells produced the large tumors and liver metastases. In addition, over-expression of AMF leads to down-regulation of E-cadherin expression associated with the up-regulation of the zinc-finger transcription factor SNAIL expression. Conclusions: The data submitted here show that AMF expression significantly contributes to the aggressive phenotype of human pancreatic cancer and thus may provide a novel prognostic and therapeutic target.

Thickness of subcutaneous fat as a strong risk factor for wound infections in elective colorectal surgery: impact of prediction using preoperative CT.

Background/Aims:In this study, we have attempted to identify and assess factors that would be most predictive of postoperative incisional surgical site infection (SSI) in colorectal surgery, including representative markers for nutrition or obesity. Methods: 152 patients who underwent elective colorectal resection were identified for inclusion in this study. The outcome of interest was incisional SSI. Variables thought to be predictive of incisional SSI, including body mass index (BMI) and the thickness of subcutaneous fat (TSF), were assessed by univariate and multivariate analysis. TSF was evaluated preoperatively using computed tomography (CT). Results: The study’s overall incidence of incisional SSI following a colorectal operation was 29 (19.1%). TSF was independently associated with incisional SSI. While BMI was significantly associated with incisional SSI on univariate analysis, this variable lost its significance on multivariate analysis that included TSF. Other nutritional markers were not significantly associated with the risk of incisional SSI. Conclusions:Our results suggest that the risk of incisional SSI increases with obesity, and that the most useful predictor of incisional SSI is TSF, as evaluated by preoperative CT. These findings indicate that CT is useful for the evaluation of TSF and the prediction of the risk of incisional SSI.

Differential regulation of phosphoglucose isomerase/autocrine motility factor activities by protein kinase CK2 phosphorylation

Phosphoglucose isomerase (PGI; EC 5.3.1.9) is a cytosolic housekeeping enzyme of the sugar metabolism pathways that plays a key role in both glycolysis and gluconeogenesis. PGI is a multifunctional dimeric protein that extracellularly acts as a cytokine with properties that include autocrine motility factor (AMF)-eliciting mitogenic, motogenic, and differentiation functions, and PGI has been implicated in tumor progression and metastasis. Little is known of the biochemical regulation of PGI/AMF activities, although it is known that human PGI/AMF is phosphorylated at Ser185 by protein kinase CK2 (CK2); however, the physiological significance of this phosphorylation is unknown. Thus, by site-directed mutagenesis, we substituted Ser185 with aspartic acid (S185D) or glutamic acid (S185E), which introduces a negative charge and conformational changes that mimic phosphorylation. A Ser-to-Ala mutant protein (S185A) was generated to abolish phosphorylation. Biochemical analyses revealed that the phosphorylation mutant proteins of PGI exhibited decreased enzymatic activity, whereas the S185A mutant PGI protein retained full enzymatic activity. PGI phosphorylation by CK2 also led to down-regulation of enzymatic activity. Furthermore, CK2 knockdown by RNA interference was associated with up-regulation of cellular PGI enzymatic activity. The three recombinant mutant proteins exhibited indistinguishable cytokine activity and receptor-binding affinities compared with the wild-type protein. In both in vitro and in vivo assays, the wild-type and S185A mutant proteins underwent active species dimerization, whereas both the S185D and S185E mutant proteins also formed tetramers. These results demonstrate that phosphorylation affects the allosteric kinetic properties of the enzyme, resulting in a less active form of PGI, whereas non-phosphorylated protein species retain cytokine activity. The process by which phosphorylation modulates the enzymatic activity of PGI thus has an important implication for the understanding of the biological regulation of this key glucose metabolism-regulating enzyme.

Regulation of Phosphoglucose Isomerase/Autocrine Motility Factor Activities by the Poly(ADP-Ribose) Polymerase Family-14

Phosphoglucose isomerase (PGI; EC 5.3.1.9) is a ubiquitous cytosolic enzyme essential for glycolysis and gluconeogenesis. PGI is a multifunctional dimeric protein that extracellularly acts as a cytokine [autocrine motility factor (AMF)] eliciting mitogenic, motogenic, and differentiation functions through binding to its cell surface receptor gp78/AMF receptor (AMFR). AMFR contains a seven-transmembrane domain with RING-H2 and leucine zipper motifs showing ubiquitin protein ligase (E3) activity and is exposed on the endoplasmic reticulum surface. Augmented expressions of both PGI/AMF and AMFR have been implicated in tumor progression and metastasis, and an intracellular binding partner of PGI/AMF is expected to regulate in part its diverse biological functions. Thus, we screened a cDNA library using a yeast two-hybrid system to search for interacting protein(s) and report on the finding of poly(ADP-ribose) polymerase-14 (PARP-14) to be a binding partner with PGI/AMF. PARP-14-PGI/AMF interaction was confirmed by coimmunoprecipitation and immunolocalization. We also report that PGI/AMF degradation is mainly regulated by the ubiquitin-lysosome system and RNA interference experiments revealed that PARP-14 inhibits PGI/AMF ubiquitination, thus contributing to its stabilization and secretion. This newly characterized PARP-14 protein should assist in understanding the regulation of PGI/AMF intracellular function(s) and may provide a new therapeutic target for inhibition of PGI/AMF inducing tumor cell migration and invasion during metastasis.

Serum Albumin Is Superior to Prealbumin for Predicting Short-Term Recurrence in Patients with Operable Colorectal Cancer

The relationship between preoperative prealbumin and cancer survival has not been fully elucidated. The purpose of this study was to examine the relationship between preoperative nutritional conditions, including prealbumin and albumin concentrations, and the risk of recurrence in cases with operable colorectal carcinoma. One hundred fifty-eight patients who underwent elective colorectal resection were analyzed in this study. Of the eligible cases, 56 (35.4%) had decreased serum prealbumin and 15 (9.5%) had decreased serum albumin preoperatively. Among 158 cases in this study, 18 (11.4%) had disease recurrence. In the univariate analysis, the depth of tumor invasion, lymph node metastasis, lymphovascular invasion, serum albumin, prealbumin, and carcinoembryonic antigen were the factors significantly associated with disease recurrence. Multivariate analysis demonstrated that only serum albumin was a predictor of the recurrence; however, serum prealbumin lost its significance on multivariate analysis. Time to tumor recurrence by Kaplan-Meier curves significantly differed among patients with low serum albumin and prealbumin level. Our results suggest that prealbumin and albumin may be sensitive indicators of the risk of recurrent disease; however, low serum albumin levels are more useful than prealbumin in predicting short-term disease recurrence in operable colorectal cancer.

Transient silencing of galectin-3 expression promotes both in vitro and in vivo drug-induced apoptosis of human pancreatic carcinoma cells

Pancreatic cancer demonstrates a strong resistance to anticancer drugs, presumably due to its resistance to drug induced apoptosis. Although gemcitabine (GEM) might be partially effective for treating advanced pancreatic cancer, its efficacy is still less than satisfactory. Galectin-3 (gal-3), a member of the β-galactoside-binding protein family, is a multifunctional protein with roles in tumor cell adhesion, proliferation, differentiation, angiogenesis, metastasis, and apoptosis. We have utilized gal-3 small interfering RNA (siRNA) to probe whether gal-3 regulates anticancer drug-induced apoptosis in pancreatic cancer cells. We found that Gal-3 siRNA augmented GEM- and cisplatin-induced apoptosis in pancreatic cancer cell lines in vitro. Mitochondrial depolarization induction was increased in gal-3-silenced cells after GEM treatment, resulting in activation of caspase-9, but not caspase-8. Akt phosphorylation was significantly downregulated in gal-3- silenced cells in association with apoptosis. Moreover, intratumoral administration of gal-3 siRNA increased the GEM sensitivity of tumor xenografts produced by subcutaneous inoculation of pancreatic cancer cells into nude mice. These results suggest that gal-3 might provide a novel therapeutic target in pancreatic cancer.