Kazufumi Sakurama

Inhibition of focal adhesion kinase as a potential therapeutic strategy for imatinib-resistant gastrointestinal stromal tumor

Focal adhesion kinase (FAK) is often up-regulated in a variety of malignancies, including gastrointestinal stromal tumor (GIST), and its overexpression seems to be associated with tumor progressiveness and poor prognosis. GIST is well known to have a mutation to c-KIT; thus, a specific c-KIT inhibitor (imatinib) is recognized as the first-line chemotherapy for GIST, although a certain type of c-KIT mutation reveals a resistance to imatinib due to as yet uncertain molecular mechanisms. To assess the c-KIT mutation-related variation of cellular responses to imatinib, murine lymphocyte-derived Ba/F3 cells, which are stably transduced with different types of c-KIT mutation, were treated with either imatinib or a FAK inhibitor (TAE226), and their antitumor effects were determined in vitro and in vivo. A mutation at exon 11 (KITdel559-560) displayed a high sensitivity to imatinib, whereas that at exon 17 (KIT820Tyr) showed a significant resistance to imatinib in vitro and in vivo. KIT820Tyr cells appeared to maintain the activities of FAK and AKT under the imatinib treatment, suggesting that FAK might play a role in cell survival in imatinib-resistant cells. When FAK activity in those cells was inhibited by TAE226, cell growth was equally suppressed and the cells underwent apoptosis regardless of the c-KIT mutation types. Oral administration of TAE226 significantly diminished tumor growth in nude mice bearing KIT820Tyr xenografts. In summary, c-KIT mutation at exon 17 displayed a resistance to imatinib with maintained activations of FAK and subsequent survival signals. Targeting FAK could be a potential therapeutic strategy for imatinib-resistant GISTs. [Mol Cancer Ther 2009;8(1):127–34]

Dual-Tyrosine Kinase Inhibitor for Focal Adhesion Kinase and Insulin-like Growth Factor-I Receptor Exhibits Anticancer Effect in Esophageal Adenocarcinoma In vitro and In vivo

Purpose: Focal adhesion kinase (FAK) regulates integrin and growth factor–mediated signaling pathways to enhance cell migration, proliferation, and survival, and its up-regulation correlates malignant grade and poor outcome in several types of cancer. In this study, we aimed to raise a potential therapeutic strategy using a FAK inhibitor for Barretts esophageal adenocarcinoma. Experimental Design: The expression status of FAK in clinical Barretts esophageal adenocarcinoma tissues was determined by immunohistochemistry. Cultured esophageal adenocarcinoma cells were treated with TAE226, a specific FAK inhibitor with an additional effect of inhibiting insulin-like growth factor-I receptor (IGF-IR), to assess its anticancer effect in vitro. Western blot was carried out to explore a participating signaling pathway for TAE226-induced cell death. Furthermore, TAE226 was orally administered to s.c. xenograft animals to investigate its anticancer effect in vivo. Results: Strong expression of FAK was found in 94.0% of Barretts esophageal adenocarcinoma compared with 17.9% of Barretts epithelia, suggesting that FAK might play a critical role in the progression of Barretts esophageal adenocarcinoma. When esophageal adenocarcinoma cells were treated with TAE226, cell proliferation and migration were greatly inhibited with an apparent structural change of actin fiber and a loss of cell adhesion. The activities of FAK, IGF-IR, and AKT were suppressed by TAE226 and subsequent dephosphorylation of BAD at Ser136 occurred, resulting in caspase-mediated apoptosis. In vivo tumor volume was significantly reduced by oral administration of TAE226. Conclusions: These results suggest that TAE226, a dual tyrosine kinase inhibitor for FAK and IGF-IR, could become a new remedy for Barretts esophageal adenocarcinoma.

Colonic interposition and supercharge for esophageal reconstruction.

AimsWe evaluated the techniques of colonic interposition and supercharge for esophageal reconstruction and discussed the main considerations related to these procedures.Patients and methodsIn this study, we performed 51 esophageal reconstructions using colonic interposition. Twenty-eight of the 51 patients had synchronous or allochronic gastric malignancy. We selected colonic interposition for high anastomosis in 11 patients and also for esophageal bypass in 3 patients. This procedure was also selected to preserve gastric function in 5 patients. We recently performed the supercharge technique for colonic interposition in 41 patients.ResultsDespite the long duration and multistep nature of the operation procedure, no perioperative complications were noted. The patients returned to a good quality of life. The incidence of postoperative weight loss did not differ significantly between the colonic reconstruction group and the gastric reconstruction group. In terms of heartburn and dumping syndrome, the outcome was markedly better in the colonic reconstruction group (no cases of heartburn or dumping syndrome) than that in the gastric reconstruction group.ConclusionFor reconstruction of the esophagus, the colonic interposition and supercharge technique is advantageous and contributes to the patient’s quality of life.

HSP90 and its inhibitors.

The HSP90 molecular chaperone family is highly conserved and expressed in various organisms ranging from prokaryotes to eukaryotes. HSP90 proteins play essential housekeeping functions, such as controlling the activity, turnover and trafficking of various proteins, promoting cell survival through maintaining the structural and functional integrity of some client proteins which control cell survival, proliferation and apoptosis, and play an important role in the progression of malignant disease. HSP90 proteins are ATP-dependent chaperones and the binding and hydrolysis of ATP are coupled to conformation changes of HSP90, which facilitate client protein folding and maturation. Many natural and synthetic molecular compounds have been proposed as promising cancer therapy via disrupting the formation of complex ATP-HSP90-client proteins.

Antiproliferative effect of a novel mTOR inhibitor temsirolimus contributes to the prolonged survival of orthotopic esophageal cancer-bearing mice

Esophageal squamous cell carcinoma (ESCC) remains one of the most aggressive cancers with poor prognosis regardless of a several reports that indicate a better therapeutic efficacy using some new chemotherapeutic agents. Recent drug development has contributed to an improved specificity to suppress mTOR activity by which many types of malignancies can be explosively progressed. Temsirolimus (CCI-779, TricelTM) is one of recently synthesized analogs of rapamycin and has provided better outcomes for patients with renal cell carcinoma. In this study, we experimentally evaluated an efficacy of targeting mTOR by temsirolimus for ESCC treatment, with an assessment of its survival advantage using an advanced ESCC animal model. First, we confirmed that the expression of phosphorylated mTOR was increased in 46 of 58 clinical ESCC tumor tissues (79.3%) and appeared to get strengthened with tumor progression. All of ESCC cell lines used in this study revealed an increase of mTOR phosphorylation, accompanied with the upregulation of hypoxia inducible factor-I α (HIF-1α), one of the critical effectors regulated by mTOR. Temsirolimus treatment apparently suppressed the activation of mTOR and its downstream effectors, resulting in the reduced ability of ESCC cell proliferation. Finally, the weekly administration of temsirolimus significantly diminished the size of subcutaneous tumors (vehicle, 3261.6 ± 722.0; temsirolimus, 599.2 ± 122.9; p = 0.007) in nude mice and effectively prolonged orthotopic esophageal cancer-bearing mice (median survival periods: control, 31 d; temsirolimus, 43 d; p = 0.0024). These data suggests that targeting mTOR by temsirolimus may become a therapeutic alternative for esophageal cancer, with a contribution to a better outcome.

The establishment of a new mouse model with orthotopic esophageal cancer showing the esophageal stricture

We established a promising new experimental animal model with an orthotopic xenograft of esophageal cancer that successfully represents poor oral intake, a major clinical feature of esophageal cancer. The advantage of this model is that no surgical technique is required, only the injection of a cell suspension by a needle and syringe via the esophageal lumen from the mouth, which provides a high reproducibility of tumor implantation and a rapid progress of outcome. We propose that this model is useful to study cancer-related outcomes and for developing new therapies for esophageal cancer, and we expect it to make a contribution to clinical practice.

F-18 FDG-PET/CT Contributes to More Accurate Detection of Lymph Nodal Metastasis From Actively Proliferating Esophageal Squamous Cell Carcinoma

Purpose: Evaluating the status of disease progression is critical for planning a therapeutic strategy for esophageal cancer. In this regard, F-18 fluorodeoxyglucose-labeled positron emission tomography (PET) is one of the most useful diagnostic modalities. However, there is room to improve its diagnostic performance, such as distinguishing lymph nodal metastases from false positives. In this study, we examined the diagnostic accuracy of fluorodeoxyglucose PET accompanied by computed tomography imaging (PET/CT) to detect regional lymph nodal metastasis from esophageal squamous cell carcinoma (ESCC). Methods: A total of 102 patients diagnosed as ESCC were subjected to this study. These patients had a preoperative PET/CT examination to evaluate the existence of metastasis. The values of maximum standardized uptake value (SUVmax) in primary tumors and in metastasized lymph nodes were measured to analyze their relationship with various clinicopathologic characteristics including the status of tumor cell proliferation, which was assessed by immunohistochemistry for Ki-67. Results: The SUVmax of the primary tumor was positively correlated with tumor size and vessel invasion, and was positively related with the SUVmax of lymph nodal metastasis, especially in cases of poorly differentiated ESCC. The SUVmax of metastasized lymph nodes was higher in larger-sized metastasized lymph nodes, whereas the Ki-labeling index of lymph nodal metastasis was positively related with the SUVmax per unit area (SUVmax/mm2). The diagnostic accuracy of PET/CT (87.3%) was higher than that of conventional CT scans (78.4%). Conclusions: The improved diagnostic accuracy of PET/CT can be explained by its ability to detect actively progressive metastasis at an early phase regardless of size.

Jejunal interposition reconstruction with a stomach preserving esophagectomy improves postoperative weight loss and reflux symptoms for esophageal cancer patients

BACKGROUND Conventional reconstruction after an esophagectomy uses a gastric tube, which commonly causes several postoperative complaints such as gastric acid reflux in long-term survival cases. Intestinal interposition between the remnant esophagus and the stomach is an option to reduce complaints, and in this study, the advantages of jejunal interposition reconstruction with a stomach preserving esophagectomy (SPE) were assessed. MATERIALS AND METHODS Eleven cases of jejunal interposition with an SPE and 16 cases with gastric tube reconstruction as a control were subject to a comparison of operation time, amount of bleeding, postoperative quality of life, and endoscopic findings. RESULTS The SPE group had a longer operation time (SPE: 560 ± 121 min, control 414 ± 83 min, P = 0.038), whereas there was no significant difference in blood loss. Postoperative weight loss was significantly recovered in the SPE group (SPE versus control = 94.0 ± 5.4% versus 87.5 ± 4.7% at 3 mo, P = 0.017; 97.2 ± 7.5% versus 85.0 ± 5.2% at 6 mo, P = 0.010), and there was a significant decrease in the occurrence of reflux symptoms such as heartburn, odynophagia, and cough when jejunal interposition with an SPE was done. Furthermore, reflux esophagitis and Barretts epithelium were found in six out of 12 cases (50%) of the control group by postoperative endoscopy, while no cases in the SPE group had either condition (P < 0.01). CONCLUSIONS This reconstruction method is a promising option to improve postoperative quality of life, mainly due to the long-term elimination of reflux esophagitis, which assists in the recovery of postoperative weight loss.

Oral administration of FAK inhibitor TAE226 inhibits the progression of peritoneal dissemination of colorectal cancer

Peritoneal dissemination is one of the most terrible types of colorectal cancer progression. Focal adhesion kinase (FAK) plays a crucial role in the biological processes of cancer, such as cell attachment, migration, proliferation and survival, all of which are essential for the progression of peritoneal dissemination. Since we and other groups have reported that the inhibition of FAK activity exhibited a potent anticancer effect in several cancer models, we hypothesized that TAE226, a novel ATP-competitive tyrosine kinase inhibitor designed to target FAK, can prevent the occurrence and progression of peritoneal dissemination. In vitro, TAE226 greatly inhibited the proliferation and migration of HCT116 colon cancer cells, while their adhesion on the matrix surface was minimally inhibited when FAK activity and expression was suppressed by TAE226 and siRNA. In vivo, when HCT116 cells were intraperitoneally inoculated in mice, the cells could attach to the peritoneum and begin to grow within 24 h regardless of the pretreatment of cells with TAE226 or FAK-siRNA, suggesting that FAK is not essential, at least for the initial integrin-matrix contact. Interestingly, the treatment of mice before and after inoculation significantly suppressed cell attachment to the peritoneum. Furthermore, oral administration of TAE226 greatly reduced the size of disseminated tumors and prolonged survival in tumor-bearing mice. Taken together, a possible strategy for inhibiting peritoneal dissemination by targeting FAK with TAE226 appears to be applicable through anti-proliferative and anti-invasion/anti-migration mechanisms.

Involvement of focal adhesion kinase in the progression and prognosis of gastrointestinal stromal tumors

Gastrointestinal stromal tumors often express gene mutations to c-KIT and platelet-derived growth factor receptor-alpha, both of which result in constitutive activations of their signaling pathways that are quite essential for the proliferation and survival of tumor cells in most clinical gastrointestinal stromal tumors. Targeting these molecules provides a dramatic improvement to therapeutic strategy. To identify a new therapeutic target for gastrointestinal stromal tumor treatment, we focused on focal adhesion kinase, which is reported to be an up-regulated gene in clinical gastrointestinal stromal tumors, because so far no one has examined its expression status at the protein level. In this study, Western blot analysis revealed that all 10 of the examined gastrointestinal stromal tumor tissues strongly expressed focal adhesion kinase protein and that phosphorylated focal adhesion kinase was detected in 9 of them. Next, we assessed the expression status of focal adhesion kinase and phosphorylated focal adhesion kinase in 51 cases of gastrointestinal stromal tumor by immunohistochemistry. Positive stainings for focal adhesion kinase and phosphorylated focal adhesion kinase were confirmed in 44 (86.3%) and in 40 cases (78.4%) of the 51 gastrointestinal stromal tumors, respectively. We further found that the focal adhesion kinase-positive staining rate became higher along with the increased status of malignant behavior. Moreover, when the 51 gastrointestinal stromal tumors were divided into 2 groups based upon their focal adhesion kinase expression status, the 5-year overall survival of patients in the focal adhesion kinase-positive group (66.5%) was significantly poorer than that in the focal adhesion kinase-negative group (100%). These results indicate that the up-regulation of focal adhesion kinase protein may also contribute to the tumor progression of gastrointestinal stromal tumors and that focal adhesion kinase is a potential target for gastrointestinal stromal tumor treatment.