Tomoyuki Goya

Human L-type amino acid transporter 1 (LAT1) : characterization of function and expression in tumor cell lines

System L is a major nutrient transport system responsible for the transport of large neutral amino acids including several essential amino acids. We previously identified a transporter (L-type amino acid transporter 1: LAT1) subserving system L in C6 rat glioma cells and demonstrated that LAT1 requires 4F2 heavy chain (4F2hc) for its functional expression. Since its oncofetal expression was suggested in the rat liver, it has been proposed that LAT1 plays a critical role in cell growth and proliferation. In the present study, we have examined the function of human LAT1 (hLAT1) and its expression in human tissues and tumor cell lines. When expressed in Xenopus oocytes with human 4F2hc (h4F2hc), hLAT1 transports large neutral amino acids with high affinity (K(m)= approximately 15- approximately 50 microM) and L-glutamine and L-asparagine with low affinity (K(m)= approximately 1.5- approximately 2 mM). hLAT1 also transports D-amino acids such as D-leucine and D-phenylalanine. In addition, we show that hLAT1 accepts an amino acid-related anti-cancer agent melphalan. When loaded intracellularly, L-leucine and L-glutamine but not L-alanine are effluxed by extracellular substrates, confirming that hLAT1 mediates an amino acid exchange. hLAT1 mRNA is highly expressed in the human fetal liver, bone marrow, placenta, testis and brain. We have found that, while all the tumor cell lines examined express hLAT1 messages, the expression of h4F2hc is varied particularly in leukemia cell lines. In Western blot analysis, hLAT1 and h4F2hc have been confirmed to be linked to each other via a disulfide bond in T24 human bladder carcinoma cells. Finally, in in vitro translation, we show that hLAT1 is not a glycosylated protein even though an N-glycosylation site has been predicted in its extracellular loop, consistent with the property of the classical 4F2 light chain. The properties of the hLAT1/h4F2hc complex would support the roles of this transporter in providing cells with essential amino acids for cell growth and cellular responses, and in distributing amino acid-related compounds.

A Japanese Lung Cancer Registry Study: Prognosis of 13,010 Resected Lung Cancers

Purpose: The validation of tumor, node, metastasis staging system in terms of prognosis is an indispensable part of establishing a better staging system in lung cancer. Methods: In 2005, 387 Japanese institutions submitted information regarding the prognosis and clinicopathologic profiles of patients who underwent pulmonary resections for primary lung neoplasms in 1999 to the Japanese Joint Committee of Lung Cancer Registry. The data of 13,010 patients with only lung carcinoma histology (97.6%) were analyzed in terms of prognosis and clinicopathologic characteristics. Results: The 5-year survival rate of the entire group was 61.4%. For the small cell histology (n = 390), the 5-year survival rates according to clinical (c) and pathologic (p) stages were as follows: 58.8% (n = 161) and 58.3% (n = 127) for IA, 58.0% (n = 77) and 60.2% (n = 79) for IB, 47.1% (n = 17) and 40.6% (n = 29) for IIA, 25.3% (n = 38) and 41.1% (n = 29) for IIB, 29.0% (n = 61) and 28.3% (n = 60) for IIIA, 36.3% (n = 19) and 34.6% (n = 40) for IIIB, and 27.8% (n = 12) and 30.8% for IV (n = 13). For the non-small cell histology (n = 12,620), the 5-year survival rates according to c-stage and p-stage were as follows: 77.3% (n = 5642) and 83.9% (n = 4772) for IA, 59.8% (n = 3081) and 66.3% (n = 2629) for IB, 54.1% (n = 205) and 61.0% (n = 361) for IIA, 43.9% (n = 1227) and 47.4% (n = 1330) for IIB, 38.3% (n = 1628) and 32.8% (n = 1862) for IIIA, 32.6% (n = 526) and 29.6% (n = 1108) for IIIB, and 26.5% (n = 198) and 23.1% (n = 375) for IV. Adenocarcinoma, female gender, and age less than 50 years were significant favorable prognostic factors. Conclusion: This large registry study provides benchmark prognostic statistics for lung cancer. The prognostic difference between stages IB and IIA was small despite different stages. Otherwise, the present tumor, node, metastasis staging system well characterizes the stage-specific prognoses.

The Importance of Surgery to Non-Small Cell Carcinoma of Lung with Mediastinal Lymph Node Metastasis

In the past 25 years, 1,654 patients with non-small cell cancer underwent resection at National Cancer Center Hospital, Tokyo. A comparative study has been made of 5-year survival of patients who had pulmonary resection with and without mediastinal lymph node dissection. There were 426 patients (25.8% of the total) with N2 M0 disease. Of these, 345 underwent pulmonary resection with mediastinal lymph node dissection. The 5-year survival in this group was 15.9% (T1 N2 M0, 30.0%; T2 N2 M0, 14.5%; and T3 N2 M0, 12.9%). In the remaining 81 patients, who did not have mediastinal lymph node dissection, 5-year survival was 6.7%. Of the 426 patients with N2 M0 disease, 242 were select patients who underwent a curative operation with an overall 5-year survival of 19.2%. Sixty-six of them had squamous cell carcinoma and a 5-year survival of 30.8%; 153 had adenocarcinoma and a survival of 16.0%; 14 had large cell carcinoma and a survival of 12.8%; and 9 had adenosquamous cell carcinoma, and none survived 5 years. To improve the end results, it is important to perform as many curative operations with mediastinal lymph node dissection as possible. Histological cell type and tumor status must be taken into consideration.

Autophagy Is Activated in Colorectal Cancer Cells and Contributes to the Tolerance to Nutrient Deprivation

Several types of cancer cells, including colorectal cancer-derived cell lines, show austerity, the resistance to nutrient starvation, but exactly how cancer cells obtain energy sources under conditions in which their external nutrient supply is extremely limited remains to be clarified. Because autophagy is a catabolic process by which cells supply amino acids from self-digested organelles, cancer cells are likely to use autophagy to obtain amino acids as alternative energy sources. Amino acid deprivation-induced autophagy was assessed in DLD-1 and other colorectal cancer-derived cell lines. The autophagosome-incorporated LC3-II protein level increased after treatment with a combination of autolysosome inhibitors, which interferes with the consumption of autophagosomes. Autophagosome formation was also morphologically confirmed using ectopically expressed green fluorescent protein-LC3 fusion proteins in DLD-1 and SW480 cells. These data suggest that autophagosomes were actively produced and promptly consumed in colorectal cancer cells under nutrient starvation. Autolysosome inhibitors and 3-methyl adenine, which suppresses autophagosome formation, remarkably enhanced apoptosis under amino acid-deprived and glucose-deprived condition. Similar results were obtained in the cells with decreased ATG7 level by the RNA interference. These data suggest that autophagy is pivotal for the survival of colorectal cancer cells that have acquired austerity. Furthermore, autophagosome formation was seen only in the tumor cells but not in the adjacent noncancerous epithelial cells of colorectal cancer specimens. Taken together, autophagy is activated in colorectal cancers in vitro and in vivo, and autophagy may contribute to the survival of the cancer cells in their microenvironment.

A review of 79 thymomas: modification of staging system and reappraisal of conventional division into invasive and non-invasive thymoma.

A clinicopathological study of surgically resected thymomas was performed using Masaokas staging and modified Masaokas staging systems, and the utility of these two staging systems was compared. The modification enabled adjustment for the disproportion in the number of cases between Stage I and Stage II. Analysis of survival rates, according to the tumor stage, indicated that the old classification should be reappraised, that is, division into non‐invasive and invasive thymomas, although staging may contribute to the indication for postoperative radiotherapy, especially for Stage II disease. Analysis of the cases showed a wide spectrum of aggressiveness, varying from cases showing slow progression with a relatively favorable prognosis, such as the spindle cell type, to cases with rapid progression leading to tumor death in a relatively short time, such as the epithelial cell predominant and polygonal cell type. The pathological stage at the time of first surgical resectlon would reflect the degree of aggressiveness of thymoma in many instances. Therefore, not only staging the tumor extent but also grading of its aggressiveness are needed in order to predict the prognosis of patients with thymoma. For the latter, histology and cytopathology are helpful.

Extended resection of the left atrium, great vessels, or both for lung cancer

One hundred one patients with locally advanced lung cancer underwent combined resection of the lung and the left atrium with or without the great vessels. A single additional organ was resected in 92 patients, two organs in 8 patients, and three organs in 1 patient. The left atrium was resected in 44 patients, the superior vena cava in 32, the adventitia of the aorta in 21, the aorta in 7, and the pulmonary artery in 7. The most important factors affecting survival defined by multivariate analysis were postoperative pneumonia, complete resection, postoperative bleeding, and lymph node metastasis (p < 0.05). Thirteen patients survived 3 years or more and 10 of the 13 survived 5 years or more. The 5-year survival rate for all patients, including 8 with operative death, was 13%, and the median survival time was 9.2 months. The 5-year survival and median survival time were 19% and 13.8 months after complete resection and 0% and 6.5 months after incomplete resection (p < 0.01). The 5-year survival and median survival time for patients with pathologic stage IIIA, IIIB, and IV were 16.8% and 16.8 months; 18.3% and 9.8 months; and 0% and 5.4 months, respectively. There was a significant difference between stages IIIA plus IIIB and stage IV (p < 0.05). The 5-year survival after left atrium resection was 22%. Extended resection was worthwhile for the patients undergoing complete resection and without postoperative complications.

Pulmonary Resection in Patients Aged 80 Years or Over with Clinical Stage I Non-small Cell Lung Cancer: Prognostic Factors for Overall Survival and Risk Factors for Postoperative Complications

Introduction: This retrospective study was designed to identify the predictors of long-term survival and the risk factors for complications after surgery in patients aged 80 years or older with clinical (c)-stage I non-small cell lung cancer. Methods: The Japanese Joint Committee of Lung Cancer Registry collated the clinicopathological profiles and outcomes of 13,344 patients who underwent pulmonary resection for primary lung cancer in 1999. The data of 367 patients aged 80 years or older with c-stage I non-small cell lung cancer were analyzed for prognostic factors and risk factors for postoperative complications. Results: The median age was 82 years (range, 80-90 years). Of the total patient number, 102 (27.8%) had some form of comorbidity diagnosed preoperatively. Thirty-one (8.4%) patients presented with postoperative complications, and the operative mortality was 1.4%. The 5-year survival rates were 55.7% for c-stage I patients, 62.0% for c-stage IA, and 47.2% for c-stage IB. Advanced pathologic stage and comorbidity were significant independent predictors of shortened survival (p < 0.0001 and p = 0.032, respectively). Comorbidity and mediastinal lymph node dissection were identified as factors that increased the risk of postoperative complications (p < 0.0001 and p = 0.036, respectively). Survival rates were independent of the extent of pulmonary resection (lobectomy or limited resection). Conclusions: Octogenarian patients with c-stage I lung cancer in this study had a satisfactory long-term outcome and low-mortality rate. Comorbidity is a factor associated with both prognosis and operative risks. A selection of the patients who would be curable without mediastinal lymph node dissection after an accurate preoperative staging is beneficial to decrease the postoperative complications because this procedure is a risk factor.

Association of point mutation in c-Ki-ras oncogene in lung adenocarcinoma with particular reference to cytologic subtypes

The correlation between clinicopathologic findings and point mutation in codon 12 of c‐Ki‐ras gene was examined in primary lung adenocarcinomas using polymerase chain reaction and oligonucleotide hybridization techniques. The mutation was detected in ten of 67 cases (15%). Microscopically, mutation‐positive cases revealed a tendency to be well differentiated (P < 0.01). Especially, the incidence of the mutation‐positive cases was significantly higher in goblet cell type (three of four) than in other types (five of 56) (P < 0.001). None of 21 cases of pure Clara cell type showed the mutation (P < 0.05). The mutation was detected frequently in tumors with no lymph node metastasis (P < 0.05), with larger tumor size (P = 0.01), and T2 cases (P < 0.01). Cigarette smoking was not always a contributing factor for mutation. This study revealed that the point mutation of c‐Ki‐ras codon 12 in lung adenocarcinoma has been associated with the cytologic subtype.

Japanese Lung Cancer Registry Study: First Prospective Enrollment of a Large Number of Surgical and Nonsurgical Cases in 2002

Purpose: To investigate prognoses of lung cancer patients prospectively enrolled in the Japan Lung Cancer Registry Study. Methods: Patients newly diagnosed as having lung cancer exclusively in 2002 were enrolled. Follow-up surveys were performed twice, in 2004 and 2009, and the final follow-up data with prognoses were analyzed for 14,695 patients (79%). Clinical stages were defined according to the sixth edition of the International Union Against Cancer-tumor, node, metastasis classification (2002). Results: The mean age was 67.1 years (range, 18-89 years), and there were 10,194 men (69.3%) and 4315 women (29.7%). The most frequent histology was adenocarcinoma (n = 8325, 56.7%), followed by squamous cell carcinoma (n = 3778, 26%) and small cell carcinoma (n = 1345, 9.2%). The distribution of clinical stages was as follows: IA, 4245 cases (29.3%); IB, 2248 (14.5%); IIA, 208 (1.4%); IIB, 918 (6.3%); IIIA, 1700 (11.8%); IIIB, 2110 (16.3%); and IV, 3037 (21.0%). The 5-year survival rates were 44.3% for all patients, 46.8% for those with non-small cell lung cancer, and 14.7% for those with small cell lung cancer. According to the clinical stage of non-small cell lung cancer and small cell lung cancer, the 5-year survival rates were 79.4 and 52.7% for stage IA, 56.9 and 39.3% for IB, 49.0 and 31.7% for IIA, 42.3 and 29.9% for IIB, 30.9 and 17.2% for IIIA, 16.7 and 12.4% for IIIB, and 5.8 and 3.8% for IV, respectively. Conclusion: Analysis of a large cohort in the Japanese registry study found that stage-specific prognosis was within a range similar to other reports. The data presented should provide an important reference for future clinical trials in Japan.

Clinicopathologic characteristics of adenosquamous carcinoma of the lung.

Fifty‐six cases of surgically resected adenosquamous carcinoma of the lung were studied clinicopathologically, and their outcome was compared with that of adenocarcinomas and squamous cell carcinomas of the lung. The frequency rate of adenosquamous carcinoma was 2.6% of 2160 primary lung cancers resected in the National Cancer Center Hospital (Tokyo, Japan). The survival curves of patients with adenosquamous carcinomas, adenocarcinomas, and squamous cell carcinomas indicated that the outcome of adenosquamous carcinoma was poorer than that of adenocarcinomas and squamous cell carcinomas, particularly in Stages I and II. The amount of adenocarcinoma component did not affect the survival rate, although the histologic features of metastatic lymph nodes was somewhat influenced by the histologic type of the primary tumors. The histologic subtype of adenosquamous carcinoma was one of the independent prognostic determinants.