Eriko Tokunaga

Deregulation of the akt pathway in human cancer

Akt (protein kinase B) is a serine/threonine kinase which is a central regulator of widely divergent cellular processes including proliferation, differentiation, migration, survival and metabolism. Akt is activated by a variety of stimuli, through growth factor receptors, in phosphatidylinositol 3-kinase (PI3K)-dependent manner. Akt is also negatively regulated by the tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN). A disruption of normal Akt/PKB/PTEN signaling frequently occurs in many human cancers, which plays an important role in cancer development, progression and therapeutic resistance. Numerous studies have revealed the blockage of Akt signaling to result in apoptosis and growth inhibition of tumor cells. Therefore, this signaling pathway, including both upstream and downstream of Akt, has recently attracted considerable attention as a new target for effective cancer therapeutic strategies. In fact, many inhibitors of Akt pathway have been identified and clinical studies of some agents are ongoing. In this review, we describe Akt signaling pathway components and its cellular functions as well as the alterations in human cancers and the therapeutic approaches for targeting the Akt pathway in cancer.

Akt is frequently activated in HER2/neu-positive breast cancers and associated with poor prognosis among hormone-treated patients.

Akt/PKB is a serine/threonine kinase that plays an important role in survival when cells are exposed to different apoptotic stimuli. Aberrant activation of Akt/PKB in breast carcinoma is associated with poor prognosis and resistance to endocrine therapy and chemotherapy. The Akt signaling pathway currently attracts considerable attention as a new target for effective therapeutic strategies. We therefore investigated the relationship between activation of Akt and clinicopathologic variables including hormone receptor and HER2/neu status. Breast cancer tissues obtained from 252 patients were utilized for this study. We evaluated Akt activation by immunohistochemical assessment of the expression of phosphorylated Akt (pAkt) at Ser‐473. Eighty‐four cases (33.3%) were diagnosed as positive for pAkt expression. pAkt was significantly associated with HER2/neu overexpression (p < 0.0001). There was an inverse correlation between pAkt and PR expression (p = 0.0321); however, there was no association between pAkt and ER expression. Survival analysis showed that pAkt positivity was associated with poor disease‐free survival in cases with postoperative hormone therapy; however, there was no association in cases without hormone therapy. Our results indicate that Akt activation induced poor prognosis in patients who received adjuvant hormone therapy. This finding suggests that inhibition of the Akt signaling pathway may increase the efficacy of hormone therapy and improve the prognosis of patients who receive adjuvant hormone therapy.

AKT phosphorylation associates with LOH of PTEN and leads to chemoresistance for gastric cancer

Growth factor receptor‐mediated signal transduction has been implicated in conferring resistance to conventional chemotherapy on cancer cells. We describe a pathway that involves AKT/PI3K to mediate chemoresistance in gastric cancer patients. Primary gastric carcinoma tissues and corresponding normal mucosa were obtained from 76 gastric cancer patients who underwent surgery in the Department of Surgery II in Kyushu University Hospital from the years 1996–2000. AKT activation was investigated by immunostaining with a phosphorylation‐specific antibody, and LOH (loss of heterozygosity) of PTEN was studied in the same samples. AKT was phosphorylated in 22 cases (28.9%) of gastric cancer cases. AKT and phosphorylated AKT were not correlated with any clinicopathological factor. We found that the gastric cancer patients who had higher AKT phosphorylation (activated AKT) seemed to have LOH of PTEN (p = 0.0008). When the chemotherapeutic sensibilities of these patients were studied in an MTT assay, it was found that the activated AKT was associated with increased resistance to multiple chemotherapeutic agents (5‐fluorouracil, adriamycin, mitomycin C and cis‐platinum). The results of our study indicate that AKT activation and LOH of PTEN plays an important role in conferring a broad‐spectrum chemoresistance in gastric cancer patients. It also indicates that AKT may therefore be a novel molecular target for therapies or chemosensitivity tests that improve the outcomes of gastric cancer patients.

Non-mass-like enhancement on contrast-enhanced breast MR imaging: Lesion characterization using combination of dynamic contrast-enhanced and diffusion-weighted MR images

PURPOSE To evaluate the diagnostic accuracy of a combination of dynamic contrast-enhanced MR imaging (DCE-MRI) and diffusion-weighted MR imaging (DWI) in characterization of lesions showing non-mass-like enhancement on breast MR imaging and to find the strongest discriminators between carcinoma and benignancy. MATERIALS AND METHODS We analyzed consecutive MR images in 45 lesions showing non-mass like enhancement in 41 patients. We analyzed lesion size, distribution, internal enhancement, kinetic curve pattern, and apparent diffusion coefficient (ADC) values. We applied univariate and multivariate analyses to find the strongest indicators for malignancy. In a validation study, 22 non-mass-like enhancement lesions in 21 patients were examined. We calculated diagnostic accuracy when we presume category 4b, 4c, and 5 lesions as malignant or high to moderate suspicion for malignancy, and category 4a and 3 as low suspicion for malignancy or benign. RESULTS Segmental distribution (P=0.018), clumped internal enhancement (P=0.005), and ADC less than 1.3 x 10(-3) mm(2)/s (P=0.047) were the strongest MR indicators of malignancy. In a validation study, sensitivity, specificity, positive predictive value, negative predictive value and accuracy were 87% (13/15), 86% (6/7), 93% (13/14), 75% (6/8) and 86% (19/22), respectively. CONCLUSION The combination of DCE-MRI and DWI showed high diagnostic accuracy in characterization of non-mass-like enhancement lesions on breast MR images.

Trastuzumab and breast cancer: developments and current status

The emergence of trastuzumab has drastically changed therapy for breast cancer. Trastuzumab (Herceptin; Genentech) is a recombinant humanized monoclonal antibody that targets an epitope in the extracellular domain of the human epidermal growth factor receptor 2 (HER2) protein. HER2 is a member of a family of four transmembrane receptor tyrosine kinases that regulate cell growth, survival, and differentiation via multiple signal transduction pathways. Overexpression of HER2 or amplification of the HER2 gene occurs in 20%–30% of human breast cancers. Preclinical models have demonstrated that this antibody has significant antitumor activity as a single agent, and it also has a synergy with certain chemotherapeutic drugs. Phase II and III clinical trials performed in women with metastatic breast cancers that overexpress HER2 have shown trastuzumab to have clinical activity when used as monotherapy, while also improving survival when used as a first-line therapy in combination with chemotherapy. At present, clinical investigations are focusing attention on the efficacy of trastuzumab in both the adjuvant and neoadjuvant setting, as well as in the metastatic setting. In this review, we describe the developments and current status of trastuzumab-based treatment for breast cancer.

Prognostic significance of Natural killer cell activity in patients with gastric carcinoma : A multivariate analysis

OBJECTIVE:Natural cytotoxicity, mediated by natural killer (NK) cells, has been believed to play an important role in inhibiting experimental tumor metastasis, and diminished NK cell activities leads to a high incidence of tumor occurrence. Despite convincing evidence from experimental studies, the role of NK cells in the immunological surveillance against cancer in human is poorly defined.METHODS:The present study was based on a retrospective analysis of data on 156 patients with gastric cancer, who were surgically treated in the Department of Surgery II, Kyushu University Hospital from 1993 to 1996. All patients were examined for NK cell activity based on a peripheral blood sampling done preoperatively.RESULTS:Significant association between NK cell activity and clinicopathological parameters including tumor size, lymphatic involvement, vascular involvement, and lymph node metastases was evident. When comparing the two groups according to NK cell activity, tumors with low NK cell activity tend to have lymphatic involvement. The 5-yr survival rates were 94.6% and 72.3% for those with NK cell activity >25% lysis and ≤25% lysis, respectively, the value being statistically significant (p < 0.05). The independent risk factors for prognosis examined by logistic regression analysis were lymphatic involvement, NK cell activity, depth of tumor invasion, and lymph node dissection.CONCLUSIONS:These current data showed that NK cell activity may be related to tumor volume and dissemination. Measurement of preoperative NK cell activity may be pertinent for the prognosis of patients with gastric cancer and for follow-up clinical management.

Reduced expression of p33ING1 and the relationship with p53 expression in human gastric cancer

Abstract p33 ING1 is a novel growth inhibitor candidate for a tumor suppressor gene. p33 ING1 cooperates with p53 and negatively regulates cell growth by activating transcription from the p21/WAF1 promoter even though it has no significant sequence similarity to p53. We first compared p33 ING1 expression in human gastric cancers and matched normal tissues using quantitative RT-PCR and real time ‘Taqman TM’ technology. A significant decrease in p33 ING1 expression was evident in 15 of 20 gastric cancers. In immunohistochemical analysis, p53 protein expression was detected in 4 of 20 (20%) tumors, and 12 of 15 (80%) tumors with decreasing p33 ING1 expression in RT-PCR had the wild type p53. When we examined the sequence of p33 ING1 in 12 gastrointestinal carcinoma cell lines, we found mutation in only one cell line, HCT116. Our findings are interpreted to mean that p33 ING1 may function as a tumor suppressor in gastric carcinogenesis, even though the gene is preserved in the majority of gastrointestinal carcinomas. It should be noted that expression of p33 decreased in many cancer patients, and the biological effects of p33 ING1 and p53 are interrelated and require the activity of both genes.

Detection of non-palpable breast cancer in asymptomatic women by using unenhanced diffusion-weighted and T2-weighted MR imaging: comparison with mammography and dynamic contrast-enhanced MR imaging

ObjectiveTo compare the detectability of non-palpable breast cancer in asymptomatic women by using mammography (MMG), dynamic contrast-enhanced MR imaging (DCE-MRI) and unenhanced MR imaging with combined diffusion-weighted and T2-weighted images (DWI + T2WI).MethodsForty-two lesions in 42 patients with non-palpable breast cancer in asymptomatic women were enrolled. For the reading test, we prepared a control including 13 normal and 8 benign cases. Each imaging set included biplane MMG, DCE-MRI and DWI + T2WI. Five readers were asked to rate the images on a scale of 0 to 100 for the likelihood of the presence of cancer and the BI-RADS category. Confidence level results were used to construct receiver operating characteristic analysis. Sensitivity and specificity were calculated for each technique.ResultsDWI + T2WI showed higher observer performances (area under the curve, AUC, 0.73) and sensitivity (50%) for the detection of non-palpable breast cancer than MMG alone (AUC 0.64; sensitivity 40%) but lower than those of DCE-MRI (AUC 0.93; sensitivity 86%). A combination of MMG and DWI + T2WI exhibited higher sensitivity (69%) compared with that of MMG alone (40%).ConclusionDWI + T2WI could be useful in screening breast cancer for patients who cannot receive contrast medium and could be used as a new screening technique for breast cancer.

Overexpression of the heat shock protein HSP70 family and p53 protein and prognosis for patients with gastric cancer.

The cell synthesis of heat shock proteins is increased by a variety of environmental and pathophysiological stressful conditions. The 70-kD heat shock protein family (HSP70 family) which constitutively expresses hsc70 and heat-inducible hsp70 is thought to be involved in protein-protein interactions, including oncogene products. We investigated the HSP70 family expression and biological behavior of gastric cancer, and its relation to p53 overexpression. Expressions of HSP70 and p53 in 164 primary gastric tumors were determined immunohistochemically. Exploratory data were analyzed on a set of 164 primary gastric cancers, and we constructed in prognostic significance of the HSP70 expression level and the relation to p53 overexpression. Expression of HSP70 (hsc70 and hsp70) were detected in nuclei and/or cytoplasm of cancer cells. Western blotting analysis showed that hsc70 and hsp70 were both expressed in five gastric cancer cell lines. Immunohistochemically stained positive cells of HSP70 varied from 0 (very weak) to 100%, in each case. The median level of positive cell rate was 19.0%. A HSP70 expression of over 19.0% was related to the differentiated tissue type of gastric cancer, but not to other clinicopathological factors. There was no difference in survival rates in subjects with higher and lower groups of HSP70 expression. HSP70 expression was also not related to p53 overexpression in the nuclei and p53 overexpression-related poorer prognosis. Our findings show that the expression of HSP70 is not associated with tumor advance-related characteristics or with the prognosis of gastric cancer. Measurements of HSP70 expression do not appear to be a useful prognostic marker.

Diminished expression of ING1 mRNA and the correlation with p53 expression in breast cancers

p33(ING1) is a novel candidate tumor suppressor and its overexpression induces growth arrest or apoptosis in different cell lines. These functions of p33(ING1) depend largely on the activity of p53, and p53-dependent activation of the transcription from the p21/WAF1 promoter also requires p33(ING1). We examined the expression of ING1 mRNA in breast cancer cell lines and clinical breast cancer tissues, using quantitative RT-PCR and real time TaqMan technology. In breast cancer cell lines, ING1 mRNA was expressed at almost the same level. However, in a comparison between the cancer and matched normal tissues, a significant decrease in ING1 mRNA expression was found in 17 of 24 (70.8%) breast cancer tissues. We also examined the correlation between ING1 mRNA expression and p53 expression. There was a significant decrease of ING1 mRNA in nine of 15 tumors negative for p53 immunostaining, most of which were considered to have wild type p53. In these tumors, p53 may not function in case of a decreased expression of p33(ING1), and the lack of cell cycle regulation may correlate with the carcinogenesis and tumor progression.