Ramucirumab for the treatment of gastroesophageal cancers.

INTRODUCTION: In 2014, the U.S. Food and Drug Administration (FDA) approved ramucirumab for use in the second line setting of advanced or metastatic, gastric or gastroesophageal adenocarcinoma (GEAC) based on the result of Phase III clinical trials; REGARD and RAINBOW. AREAS COVERED: We briefly review the mechanisms of angiogenesis, anti-angiogenic therapy, and current status of advanced GEAC treatment then highlight the challenges and future prospects of novel molecular targeted agents. EXPERT OPINION: Although both the REGARD and RAINBOW trials met their primary endpoints of significantly prolonged overall survival (OS) and progression-free survival (PFS), the magnitude of the difference is still relatively modest. Given that ramucirumab alone has a marginal effect, a combination of paclitaxel and ramucirumab is strongly preferred as a second line therapy. To maximize the impact of ramucirumab in patients with GEAC, we can leverage the recent pharmacokinetics (PK) data of ramucirumab from the REGARD and RAINBOW trials. In addition, the quest for identifying biomarkers to select patients who are likely to benefit the most should continue. It is our firm belief that taxanes should no longer be added to the frontline regimens in most cases, given the success of the taxane/ramucirumab in the second line setting.

Donor cell-derived leukemia after cord blood transplantation and a review of the literature: differences between cord blood and BM as the transplant source.

Donor cell-derived leukemia (DCL) is a rare complication of SCT. Here, we present a case of DCL following cord blood transplantation (CBT) and review the clinical features of previously reported DCL. To our knowledge, this is the first report comparing clinical characteristics of DCL from the standpoint of the transplant source, with umbilical cord blood and BM. AML and myelodysplastic syndrome (MDS) were recognized more frequently in DCL after CBT, whereas the incidence of AML and ALL was similar after BMT. The median duration between the occurrence of DCL following CBT and BMT was 14.5 and 36 months, respectively. DCL occurred in a significantly shorter period after CBT than after BMT. Abnormal karyotypes involving chromosome 7 were observed in 52.4% of CBT recipients and 17.3% of BMT recipients; this was a statistically significant difference. Particularly, the frequency of monosomy 7 was significantly higher in DCL after CBT than after BMT. The types of abnormal karyotypes in DCL following BMT were similar to those characteristically observed in adult de novo AML and MDS. DCL patients generally have a poor prognosis in both groups. SCT is the best treatment for curing DCL. DCL appears to have different clinical features according to the transplant source.

Ten cases of gastro-tracheobronchial fistula: a serious complication after esophagectomy and reconstruction using posterior mediastinal gastric tube.

Gastro-tracheobronchial fistula (GTF) is a rare but life-threatening complication specifically observed after esophagectomy and reconstruction using posterior mediastinal gastric tube. Ten cases of GTF were encountered in three hospitals in 2000-2009. Their clinicopathological, surgical, and postoperative care are summarized, together with a review of previously reported cases. GTF was classified as anastomotic leakage (n= 5), gastric necrosis (n= 4), and gastric ulcer type (n= 1). The anastomotic leakage type appeared about 2 weeks (postoperative day [POD]: 8-35) after esophagectomy, was located in the cervical or higher thoracic trachea. Breathing and pneumonia were controlled by tracheal tube placed in the distal of fistula. The gastric necrosis type was noted in patients who developed necrosis of the upper part of the gastric tube and abscess formation behind the tracheal wall, at POD 20-36 around the carina, the site of pronounced ischemia. Due to the large fistula around the carina, emergency surgery with muscle patch repair was frequently required for the control of aspiration pneumonia. Patients of the gastric ulcer type had peptic ulcer in the lesser curvature of the gastric tube, which perforated into the right bronchus long after surgery (POD 630). With respect to tracheobronchial factors, preoperative chemoradiation (three cases) and pre-tracheal node dissection (three cases) tended to increase the risk of GTF. Closure of GTF by surgery (muscle patch repair) was successful in four cases and by nonsurgical treatment in three cases. In one case, stable oral intake was achieved by bypass operation without closure of GTF. Hospital death occurred in three cases. Understanding the pathogenesis and treatment options of GTF is important for surgeons who deal with esophageal cancer.

Impact of intraperitoneal chemotherapy after gastrectomy with positive cytological findings in peritoneal washings.

BACKGROUND: There is no standard treatment available for gastric cancer patients whose sole 'non-curative factor' is positivecytological findings in peritoneal washings (CFPW). The aim of this study was to examine the safety, pharmacokinetics and efficacy for free intraperitoneal cancer cells of intraperitoneal chemotherapy with paclitaxel after gastrectomy with en bloc D2 lymph node dissection in cases of gastric cancer with positive CFPW. METHODS: Ten patients with gastric cancer who underwent gastrectomy and systemic lymphadenectomy with D2 dissection, without any other non-curative factors besides positive CFPW, were treated with early postoperative intraperitoneal paclitaxel. Intra-chemotherapeutic toxicity and operative complications were measured using NCI-CTC version 3.0. Intraperitoneal and plasma paclitaxel concentrations were measured using a high-performance liquid chromatographic assay. RESULTS: Grade 3/4 toxic effects included anemia (20%) and neutropenia (10%) that required no treatment. Operative complications were, for example, superficial surgical site infections (10%) that were treated with antibiotics. No viable cancer cells were observed in the intra-abdominal fluid 24 h after intraperitoneal administration of paclitaxel. The intraperitoneal/plasma area under the drug concentration-time curve ratio was 2,003.3:1. CONCLUSION: Intraperitoneal chemotherapy with paclitaxel is a safe and effective treatment modality for free intraperitoneal cancer cells.

Prospective randomized trial of short-term neoadjuvant chemotherapy for advanced gastric cancer.

BACKGROUND: We performed short-term neoadjuvant chemotherapy (s-NAC) to examine whether anticancer drugs can change the proliferative ability of cancer cells in gastric cancer patients. METHODS: Chemotherapy was performed for 72 h before gastrectomy in 63 gastric cancer patients. Patients were classed into four groups: Group F, 16 cases who received a single administration of 5-fluorouracil (5-FU); Group C, 15 cases who received a single administration of cis-diamminedichloroplatinum (CDDP; cisplatin); Group FC, 16 cases who received both 5-FU+CDDP; and a Control group, 16 cases who did not receive chemotherapy. We reviewed neoadjuvant biopsy tissue and gastric cancer tissue delivered by operation in these cases. The TUNEL method and immunohistochemistry with an anti-MIB-1 antibody were used to evaluate cellular apoptosis and proliferative ability, respectively. The apoptotic index (AI) and an MIB-1 index (MI) were also calculated. RESULTS: There were no differences in AI or MI in biopsy tissue between the groups. The AI of gastric cancer tissue in Group FC was significantly higher than in the other groups (P < 0.01). The MI of Group FC was significantly lower than in the other groups (P < 0.05). In addition, after s-NAC operation there was a significant inhibition of proliferative potency and an induction of apoptosis in Group FC. CONCLUSION: Combination of CDDP and 5-FU reduced proliferative potency and increased cellular apoptosis in gastric cancer cells.

Significant expression of interleukin 15 in rat experimental severe acute pancreatitis.

PURPOSE: In severe acute pancreatitis (SAP), multiple organ dysfunction syndrome is a contributor to high mortality. We recently demonstrated that the serum interleukin (IL)-15 level is a predictor of the complications and mortality in clinical SAP. The aim was to investigate the role of IL-15 in experimental SAP. MATERIALS AND METHODS: SAP was induced by retrograde injection of 3 and 20% sodium deoxycholate (DCA) into biliopancreatic ducts in rats (DCA pancreatitis). Expressions of IL-15 were evaluated by Western blotting and immunohistochemical staining. Recombinant IL-15 protein was administered intraperitoneally, and the effects were investigated. RESULTS: Western blotting revealed the expressions of IL-15 in the pancreas, liver, lung and intestine in 3% DCA pancreatitis. Immunohistochemical staining showed the expression of IL-15 in the cytoplasm of each organ. In 3% DCA pancreatitis, administration of recombinant IL-15 protein attenuated the elevation of serum alanine aminotransferase (ALT) levels and improved the morphological change of the lung 18 h after the induction of SAP. Moreover, in 20% DCA pancreatitis, IL-15 improved the elevation of serum amylase and ALT levels 6 h after the induction. CONCLUSIONS: These results suggest that IL-15 is related to organ dysfunction during SAP, and that IL-15 functions as a protective factor against the organ injuries.

Touch imprint cytology with cytokeratin immunostaining versus Papanicolau staining for intraoperative evaluation of sentinel lymph node metastasis in clinically node-negative breast cancer.

AIM: This study investigated whether intraoperative assessment of SLN status in patients with clinically node-negative breast cancer was improved using touch imprint immunohistochemistry. MATERIAL AND METHODS: Each SLN was cut into slices 2mm thick and evaluated intraoperatively by touch imprint cytology with Papanicolaou staining until the end of 2005, or by a combination of Papanicolaou staining and immunostaining with an anti-cytokeratin antibody from early 2006. RESULTS: When intraoperative cytology of SLN in 85 patients who were clinically node-negative was evaluated with Papanicolaou staining, 81 patients were diagnosed as negative and four were positive. Intraoperative cytology with Papanicolaou staining had a sensitivity of 30%, specificity of 99%, false-negative rate of 70%, false-positive rate of 1.3%, and accuracy of 90.6%. When intraoperative cytology was done with immunohistochemistry plus Papanicolaou staining for SLN evaluation, 92 patients were diagnosed as negative and 17 patients were positive. Intraoperative cytology with immunohistochemistry had a sensitivity of 79%, specificity of 98%, false-negative rate of 21%, false-positive rate of 2.2%, and accuracy of 94.5%. Compared with intraoperative cytology using Papanicolaou staining alone, the combination of immunohistochemistry and Papanicolaou staining achieved a significant increase in sensitivity and a significant decrease in the false-negative rate. CONCLUSION: Intraoperative SLN evaluation by imprint cytology with immunohistochemistry achieves a more accurate diagnosis of metastasis than imprint cytology alone. This combined method is considered useful for deciding whether to perform axillary lymph node dissection.

Esophageal cancer after distal gastrectomy.

The effect of gastrectomy on the subsequent development of esophageal cancer was investigated. Duodenogastroesophageal reflux is thought to be common in patients after distal gastrectomy, but whether this contributes to the development of esophageal cancer in such patients is controversial. We retrospectively evaluated 153 patients who underwent subtotal esophagectomy for thoracic esophageal cancer between January 2002 and July 2005. They were divided into two groups, according to whether or not they had previously undergone a gastrectomy: group 1, comprising 14 patients who had undergone gastrectomy and group 2, comprising 139 patients who had not. Clinical profiles of the patients were obtained from the medical records and the whole resected esophagus was histopathologically examined. The interval between gastrectomy and esophagectomy in group 1 was significantly shorter in the patients who had undergone gastrectomy for gastric cancer (10.5 +/- 4.2 years) than in those who had undergone gastrectomy for a peptic ulcer (28.9 +/- 3.0 years). The interval was also somehow shorter in the patients for whom anastomosis had been performed by Billroth I (21.3 +/- 5.6 years) compared with Billroth II (29.7 +/- 3.2 years), although the difference did not reach its statistical significance (P = 0.11). Moreover, the proportion of lower third tumors in patients after gastrectomy was significantly higher compared with that of the patients with intact stomach. These findings suggest that a history of gastrectomy is associated with more lower-third squamous cell esophageal carcinoma.

[A case of postoperative multiple hepatic metastasis from esophageal cancer successfully treated by surgical resection and hepatic arterial infusion chemotherapy].

A 66-year-old male who underwent radical resection for esophageal cancer (stage IV) was diagnosed with multiple hepatic metastasis 1 year and 3 months after the surgery. He underwent hepatic resection and received systemic chemotherapy (FAP: 5-FU, ADR, CDDP), as the post-operative adjuvant therapy. One year and 3 months later, there was a huge recurrence in the residual liver and hepatic arterial infusion chemotherapy (FAP) was performed. The recurrent lesion disappeared completely after 3 sessions of arterial infusion chemotherapy. The arterial infusion chemotherapy was continued in the outpatient clinic and the recurrent lesion is well controlled. At present, this patient has returned to social life, 2 years and 3 months after the hepatic resection. The utility of hepatic arterial infusion chemotherapy and hepatectomy for postoperative multiple hepatic metastasis from esophageal cancer was shown in the present case.

Role of galectin-3 in adenocarcinoma liver metastasis.

Galectin-3 is a lactosamine-specific lectin that binds to laminin sugar-sites, and up-regulated expression of galectin-3 in primary colorectal cancer is involved in cancer progression and metastasis. Inhibitory effects of cell adhesion and liver metastasis of adenocarcinoma via portal vein by lectin-binding sugar and anti-galectin-3 antibody was examined to determine the role of galectin-laminin binding in cancer liver metastasis. Highly metastatic adenocarcinoma cell lines XK4-A3 and RPMI4788 were used in in vitro cell attachment and nude mice liver metastatic experiments, and inhibitory effects of anti-galectin-3 antibody or lectin-binding sugars were examined. The in vitro adhesion assay demonstrated that the anti-galectin-3 antibody and alpha-lactose inhibited XK4-A3 and RPMI4788 cell adhesion to laminin in a dose-dependent manner. The liver metastasis of XK4-A3 and RPMI4788 was reduced 50 and 60%, respectively (P<0.001) by alpha-lactose treatment. Anti-galectin-3 antibody also inhibited liver metastasis in a dose-dependent manner, and maximum inhibition rate was 66% for XK4-A3 and 90% for RPMI4788. Galectin-3 plays an important role in liver metastasis of adenocarcinoma by the mechanisms of galectin-3 binding to laminin. Inhibition of galectin-3 on cancer cell surface induces reduced cell attachment to laminin and liver metastasis.

Ley glycolipid-recognizing monoclonal antibody inhibits procoagulant activity and metastasis of human adenocarcinoma.

Tumor procoagulant is associated with cancer at advanced stages of malignancy such as infiltration and metastasis. In the present study, we investigated the role of Ley glycolipid in the mechanism of cancer metastasis. Ley glycolipid acts as an important cofactor in the expression of the blood-coagulating activity of cancer cell-derived coagulating activity 1 (CCA-1), which is one of the known tumor procoagulants. Monoclonal antibody (MoAb) FS01, which serves as the Ley-recognizing epitope, inhibits the procoagulant activity of CCA-1 was found to dose-dependently inhibit the procoagulant activity of normal plasma induced by the human lung adenocarcinoma cell line, HAL8, which shows a high level of Ley expression. It did not, however, inhibit the procoagulant activity of the human colon cancer cell line, RPMI4788, which does not express Ley. Administration of FS01 MoAb inhibited lung metastasis of HAL8 cells, but not that of RPMI4788. The absence of antibody-dependent cellular cytotoxicity and complement-mediated cytotoxicity of FS01 MoAb against the HAL8 cell line suggests that the inhibition of HAL8 metastasis by FS01 MoAb derives from the inhibition of blood-coagulating activity of the latter. These findings indicate that Ley glycolipid plays an important role in the mechanism of cancer metastasis via the procoagulant activity of CCA-1.

Genetic detection of lymph node micrometastases in patients with gastric carcinoma by multiple-marker reverse transcriptase-polymerase chain reaction assay.

BACKGROUND: Some patients with gastric carcinoma experience local disease recurrence despite undergoing curative resection of the tumor and regional lymph nodes (LNs), suggesting the presence of occult micrometastases. To evaluate the presence of gastric carcinoma micrometastasis in patients with otherwise histologically negative LNs, the authors established and tested a multiple-marker reverse transcriptase-polymerase chain reaction (RT-PCR) assay. METHODS: The authors assessed 435 LNs from 28 patients with gastric carcinoma who underwent gastrectomy with lymphadenectomy using the multiple-marker RT-PCR assay in addition to histologic examination. Carcinoembryonic antigen (CEA), cytokeratin-20 (CK-20), and MAGE-3 gene markers were used in this assay. LNs were scored positive for metastasis if at least one marker was positive. The presence of LN micrometastases also was verified by immunohistochemistry in histologically negative and RT-PCR positive LNs. RESULTS: Sixty-nine of 435 LNs (16%) were positive for CEA (12%), CK-20 (10%), or MAGE-3 (5%). None of 16 control LNs obtained from disease free patients was positive by RT-PCR assay. Of 414 histologically negative LNs, 50 LNs (12%) were scored as positive for metastasis by the assay. Of 26 patients who underwent curative resection, the disease stage was upgraded in 10 patients by genetic diagnosis (from Stage IA to Stage IB in 5 patients, from Stage IB to Stage IIIA in 2 patients, from Stage IB to Stage IV in 1 patient, from Stage IB to Stage II in 1 patient, and from Stage II to Stage IIIB in 1 patient). In the latter 10 patients, immunohistochemistry identified LN micrometastases in 4 patients. Two patients with micrometastasis by genetic diagnosis had recurrent disease within 1 year. CONCLUSIONS: The current results indicate that the multiple-marker RT-PCR assay is a useful tool for the detection of micrometastases in regional LNs in patients with gastric carcinoma and may improve the staging system of gastric carcinoma for these patients.

Correlation of beta-catenin and cyclin D1 expression in colon cancers.

OBJECTIVE: Beta-catenin activates transcription by TCF/LEF and has been regarded as an oncogene in a wide range of malignant tumors. Among various molecules regulated by beta-catenin/Tcf, cyclin D1 is the most likely candidate for stimulation of the oncogenic pathway. The association between beta-catenin and cyclin D1 was investigated using clinical samples from colorectal cancers. METHODS: The expression of beta-catenin and cyclin D1 was investigated by immunohistochemical analyses of samples from 70 patients with colorectal cancers. In 28 of the fresh tumor samples, beta-catenin protein was separated into soluble and insoluble fractions and quantitatively correlated with cyclin D1 protein by Western blot analysis. RESULTS: Compared with noncancerous epithelium, beta-catenin and cyclin D1 were overexpressed (+) in 35 (50%) and 30 cases (43%), respectively. Cyclin D1 (+) was observed in 74% (26/35) of beta-catenin (+) cases, but only in 11% (4/35) of the beta-catenin (-) cases. Thus, there was a strong association between the expression of beta-catenin and that of cyclin D1 (p < 0.001). In the Western blot analysis, the amount of cyclin D1 correlated well with beta-catenin expression in the soluble fraction (p = 0.0016), but not with beta-catenin in the insoluble fraction or with E-cadherin expression. Beta-catenin (-)/cyclin D1 (-) cases displayed less tumor invasion than the remaining cases. However, there were no significant differences in lymph node metastasis or other clinicopathological findings. CONCLUSION: Our results indicate that beta-catenin overexpression in the cytoplasm may promote malignant transformation by triggering cyclin D1 expression in colorectal cancers.

Clinical significance of CDC25A and CDC25B expression in squamous cell carcinomas of the oesophagus.

CDC25A, CDC25B and CDC25C belong to a family of protein phosphatases which activate the cyclin-dependent kinase at different points of the cell cycle. According to accumulating evidence, CDC25A and CDC25B seem to possess oncogenic properties. We have analysed these expressions by immunohistochemistry, western blot and RT-PCR in a series of 100 patients with squamous cell carcinoma of the oesophagus. When compared with non-cancerous cells, CDC25A and CDC25B were strongly expressed in the cytoplasm of cancer cells, with positive (+) classification in 46% (46 cases) and 48% (48 cases), respectively. There was no significant correlation between CDC25A and CDC25B expression, nor was there any association with the expression of other cell cycle-regulating molecules, including cyclin D1, Rb, p16(INK4), p27(KIP1)and PCNA (proliferating cell nuclear antigen). CDC25A (+), as well as CDC25B (+), was more frequently found in patients with deeper tumour invasion and lymph node metastasis, while tumour size was correlated only with CDC25A expression. Postoperative survival was significantly poorer for CDC25A (+) patients than CDC25A (-) patients, but was not affected by the CDC25B status. Nuclear localization of CDC25A was observed in 51 cases (51%), regardless of its cytoplasmic expression, and was not associated with clinico-pathological factors or prognosis. Multivariate analysis revealed only the CDC25A status to be an independent significant prognostic factor among these biological and clinico-pathological factors. CDC25A but not CDC25B may be a new prognostic factor for squamous cell carcinoma of the oesophagus. Thus, regulation of the G1 checkpoint in the cell cycle may be important in oesophageal carcinogenesis, which may also involve many other oncogenes.

Detection of peritoneal micrometastases of gastric carcinoma with green fluorescent protein and carcinoembryonic antigen promoter.

The aim of this study was to specifically visualize micrometastases in the peritoneal cavity, which cannot be detected by conventional methods, by using enhanced Green Fluorescent Protein (EGFP) containing carcinoembryonic antigen (CEA) promoter in an upstream position. In in vitro experiments, two cell lines from human gastric cancer, MKN45 and MKN1, and a cell line from human fibrosarcoma, HT1080, were transduced with pCEA-EGFP, which contains the CEA promoter region. MKN45 and MKN1, which expressed CEA mRNA, showed positive fluorescence after transduction of pCEA-EGFP, whereas HT1080 did not. In in vivo experiments, 7 days after 10(7) MKN45 had been injected into the peritoneal cavity of BALB/c nude mice, pCEA-EGFP was transduced in the peritoneal cavity using a fusogenic liposome with the envelope protein of Hemagglutinating Virus of Japan on the surface. On the peritoneum of the abdominal wall, fluorescent nodules were detected by fluorescence stereomicroscopy. These nodules had a minimal size of approximately 0.15 mm and could not be detected by conventional stereomicroscopy or macroscopy. They were histologically confirmed to be cancer cells by H&E staining. The results suggest that visualization of peritoneal micrometastasis of gastric cancer using CEA promoter and EGFP can offer a new strategy for diagnosis of micrometastasis.

Extensive micrometastases to lymph nodes as a marker for rapid recurrence of colorectal cancer: a study of lymphatic mapping.

To provide a detailed assessment of micrometastases of colorectal cancer by anatomical mapping of regional lymph nodes (LNs), we analyzed 237 LNs from 11 patients with colorectal cancer by reverse transcription-PCR (RT-PCR) using carcinoembryonic antigen and cytokeratin 20 as genetic markers. All dissected LNs were mapped anatomically and subjected to detection assays for micrometastases. Immunohistochemical analysis was also performed using anti-pancytokeratin antibody AE1/AE3 to confirm the existence of occult cancer cells. By histological analysis, 20 of 237 LNs contained metastatic cells, and they were all positive by both immunohistochemistry and RT-PCR. Of the 217 histologically negative LNs, 14 (6.5%) harbored micrometastases by immunohistochemistry, and 57 (26.2%) were positive for at least one of the two genetic markers. Lymphatic mappings of all patients showed that micrometastases were distributed not only at the pericolic LNs but often at distant LNS: Clinical follow-up study showed that two patients developed recurrence within 1 year after surgery, and both of them had RT-PCR-positive micrometastases in not less than 70% of LNs examined. Moreover, both patients had frequent micrometastases at distant LNs, i.e., those around the root or along the inferior mesenteric artery, when compared with patients with no recurrence. Our findings suggest that genetic diagnosis using the RT-PCR method may be clinically useful along with conventional pathological diagnosis, especially when micrometastases spread to distant LNS:

Overexpression of CDC25B overrides radiation-induced G2-M arrest and results in increased apoptosis in esophageal cancer cells.

CDC25B phosphatase plays a key role in controlling G2-M progression by dephosphorylating two inhibitory residues of CDC2 and also has been suggested to have an oncogenic property. In this study, we investigated the effect of CDC25B overexpression on radiation-induced G2-M arrest and radiation sensitivity in esophageal cancer cells. TE8-CDC25B, in which CDC25B was overexpressed under an inducible system, was more radiosensitive than the vector control (TE8-neo) in a clonogenic survival assay. Without radiation, CDC25B overexpression had little effect on cell cycle fractions or growth rate. After 10-Gy radiation, TE8-CDC25B showed decreased G2-M arrest and increased apoptosis, whereas TE8-neo displayed prolonged G2-M arrest and less apoptosis. During this period, there were no differences in the protein amounts of CDC2 and cyclin B1 between the two cell lines. However, more CDC25B expression, which was reduced immediately by radiation, was sustained in TE8-CDC25B than in TE8-neo. Moreover, induction of tyrosine phosphorylation of CDC2 and reduction of CDC2 kinase activity after irradiation was less significant in TE8-CDC25B than in TE8-neo. These results indicate that cancer cells that overexpress CDC25B override G2-M arrest by retaining CDC2 kinase activity and undergo apoptosis after radiation. This may point to an effective approach toward improving radiotherapy outcomes of various cancers.

Localization of IQGAP1 is inversely correlated with intercellular adhesion mediated by e-cadherin in gastric cancers.

Down-regulation of E-cadherin function is characteristic of cancer cells and might involve the small G-protein Rho family, including Rac1 and Cdc42. IQGAP1 has been reported to be one of the target proteins of Rac1 and Cdc42. To elucidate the role of IQGAP1 in cancer-cell adhesion, its expression was investigated in 47 cases of human gastric cancer by immunohistochemistry and Western blot upon protein fractionation, especially in comparison with E-cadherin and catenin expression. In the non-cancerous columnar epithelium of the stomach, IQGAP1, as well as E-cadherin/catenin, was expressed at the cell-cell boundary. IQGAP1 was frequently observed diffusely in the cytoplasm in intestinal-type tumors (20/22 cases) but was expressed at the cell membrane in diffuse-type tumors (19/25 cases), thus showing significant association with tumor differentiation (p < 0.01). Interestingly, membranous expression of IQGAP1 was inversely correlated with that of E-cadherin (p < 0.05) or alpha-catenin (p < 0.001). These observations were consistent with the Western blot results following protein fractionation. IQGAP1 was dominantly expressed in the soluble fraction in differentiated tumors; however, in undifferentiated tumors, it was mostly in the insoluble fraction. In contrast, both E-cadherin and alpha-catenin were detected only in the insoluble fraction. Thus, subcellular localization of IQGAP1 from the cytoplasm to the cell membrane was correlated with E-cadherin dysfunction and tumor dedifferentiation in gastric carcinogenesis.