Hisaki Igarashi

PIK3CA mutation and amplification in human lung cancer

To explore the significance of phosphatidylinositol‐3‐kinase, catalytic, alpha (PIK3CA) in the carcinogenesis in human lung, mutations and copy number changes were investigated in 148 Japanese patients with primary cancer of the lung. For biological validation, the effects of exogenously expressed wild‐type and mutated PIK3CA were studied in an immortalized human airway epithelial cell line. Mutations in PIK3CA were found in five (3.6%) of the 139 available patients, and copy number gains were found in 21 (18.3%) of 115 patients, respectively. Overall, mutations or copy number gains were detected in 24 of the 106 patients (22.6%) for whom results in both analyses were available. The prevalence of copy number gains was higher in men, smokers, and in patients with squamous cell carcinoma than in the opposite categories. The copy number changes showed a trend toward higher prevalence in the earlier stages (P = 0.038). Interestingly, the presence of mutations and of copy number alterations were mutually exclusive in the present patients, implying that both entail equivalent oncogenic potential. Over‐expressed wild‐type PIK3CA and its two common mutants, K545E and H1047R, significantly enhanced the anchorage‐independent growth activity and migration activity of immortalized airway epithelium 16HBE14o– cells, but the effects of the K545E and H1047R mutants were more remarkable than those of the wild‐type. The present demonstrates an important role of PIK3CA in human lung carcinogenesis.

Molecular karyotyping of human hepatocellular carcinoma using single-nucleotide polymorphism arrays

Genomic amplification of oncogenes and inactivation of suppressor genes are critical in the pathogenesis of human cancer. To identify chromosomal alterations associated with hepatocarcinogenesis, we performed allelic gene dosage analysis on 36 hepatocellular carcinomas (HCCs). Data from high-density single-nucleotide polymorphism arrays were analysed using the Genome Imbalance Map (GIM) algorithm, which simultaneously detects DNA copy number alterations and loss of heterozygosity (LOH) events. Genome Imbalance Map analysis identified allelic imbalance regions, including uniparental disomy, and predicted the coexistence of a heterozygous population of cancer cells. We observed that gains of 1q, 5p, 5q, 6p, 7q, 8q, 17q and 20q, and LOH of 1p, 4q, 6q, 8p, 10q, 13q, 16p, 16q and 17p were significantly associated with HCC. On 6q24–25, which contains imprinting gene clusters, we observed reduced levels of PLAGL1 expression owing to loss of the unmethylated allele. Finally, we integrated the copy number data with gene expression intensity, and found that genome dosage is correlated with alteration in gene expression. These observations indicated that high-resolution GIM analysis can accurately determine the localizations of genomic regions with allelic imbalance, and when integrated with epigenetic information, a mechanistic basis for inactivation of a tumor suppressor gene in HCC was elucidated.

EPHA2/EFNA1 expression in human gastric cancer

The erythropoietin‐producing hepatocellular (EPH)A2 receptor, tyrosine kinase, is overexpressed and phosphorylated in several types of human tumors and has been associated with malignant transformation. A recent report, however, indicated that stimulation of the EPHA2 receptor ligand, ephrinA1 (EFNA1), inhibits the growth of EPHA2‐expressing breast cancer. The authors examined the expression of EPHA2 and EFNA1 using semiquantitative reverse transcription‐polymerase chain reaction (RT‐PCR) in four gastric cancer cell lines and 49 primary gastric cancer samples, as well as in normal gastric tissue. EPHA2 was more highly expressed in tumor tissue than in normal tissue in 27 cases (55%). EFNA1 was overexpressed in tumor tissue in 28 cases (57%). No significant correlation was detected between the expression levels and histologic features such as tumor size, age, vessel invasion, or lymph node involvement. However, EPHA2 overexpression was more prominent in macroscopic type 3 and 4 tumors than in type 1 or 2 advanced gastric cancer. The authors observed EPHA2 expression in three of the four gastric cancer cell lines (AGS, KATO3, and MKN74) that were examined. In one cell line, TMK1, EPHA2 expression was barely detectable using northern blotting, RT‐PCR, and western blotting. In contrast, EFNA1 was detected in all cell lines. In the gastric cancer cell lines that endogenously expressed EPHA2, stimulation with ephrinA1‐Fc led to decreased EPHA2 protein expression and increased EPHA2 phosphorylation. Finally, the growth of EPHA2‐expressing cells was inhibited by repetitive stimulation with soluble ephrinA1‐Fc. Taken together, these findings suggest that EPHA2 and EFNA1 expression may influence the behavior of human gastric cancer. (Cancer Sci 2005; 96: 42–48)

Correlation of EPHA2 overexpression with high microvessel count in human primary colorectal cancer

Evidence suggests that the erythropoietin‐producing hepatocellular (EPH) receptor tyrosine kinases (RTKs) and their ephrin (EFN) ligands are involved in human carcinogenesis. Expression of two of them, EFNA1 ligand and its receptor, EPHA2, has been proposed to contribute to tumor‐induced neovascularization. Colorectal cancers were examined for expressions of EPHA2 and its ligand EFNA1 by semi‐quantitative RT‐PCR, and double‐immunostained for EPHA2 and CD34. Microvessels in the tumors were counted. Double‐staining was also performed in 25 cases of adenoma with focal cancer for comparison. Trends of overexpression of both EPHA2 and EFNA1 was found in tumor tissue compared to the corresponding normal tissue in the same specimen [22/37 (59.5%) and 25/37 (67.5%), respectively; P=0.100 for EPHA2 and P=0.009 for EFNA1]. Overexpression of EPHA2 and EFNA1 was noted more frequently in the early stage than in the late stage [EPHA2, 15/21 (71.4%) vs. 7/16 (43.8%), P=0.007; EFNA1, 15/21 (71.4%) vs. 10/16 (62.5%), P=0.007]. Both EPHA2 and EFNA1 were more frequently overexpressed in smaller tumors (less than 5 cm) than in larger tumors [EPHA2, 15/21 (71.4%) vs. 7/16 (43.8%), P=0.017; EFNA1, 16/21 (76.2%) vs. 8/16 (50%), P=0.001]. Tumors less than 5 cm in diameter and in stages I and II were significantly more likely to overexpress EPHA2 and EFNA1 (P=0.001 for EPHA2, P=0.001 for EFNA1). Microvessel counts (MVCs) after immuno‐staining for CD34 were significantly correlated (r=0.343, P=0.037) with overexpression of EPHA2. EPHA2‐expressing focal cancer also surrounded microvessels in adenomas with focal cancers. These findings suggest an involvement of EPHA2 in colon carcinogenesis, mainly in stages I and II, and probably through their effect on microvessel induction.

Expression of high-mobility group-1 mRNA in human gastrointestinal adenocarcinoma and corresponding non-cancerous mucosa

An 1194‐nucleotide complementary DNA clone, FMI, encoding a human high‐mobility group‐I protein (HMG‐I) was isolated from a well‐differentiated human gastric‐carcinoma cell line complementary DNA library by a differential screening method. FMI is similar to the published human HMG‐I in mature protein, with only 3 different codons at positions 11, 149, and 190. We analyzed 33 gastric and colorectal adenocarcinomas for expression of the FMI gene. Northern‐blot analysis revealed that all of the cancers expressed FMI at a higher level than in corresponding non‐cancerous mucosa, with 2 transcripts of approximately 1.4 and 2.4 kilobases. The FMI expression level in the non‐cancerous tissues increased with the depth of accompanying cancer invasion. Only 18.2% of well‐differentiated cancers showed a higher expression level in corresponding non‐cancerous tissues, whereas the expression in corresponding non‐cancerous tissues was significantly higher in moderately (60%) and poorly differentiated (83.3%) cancers. In situ hybridization demonstrated the location of FMI mRNA in well‐ and poorly differentiated gastric‐cancer cells as well as in non‐cancerous tissue adjacent to poorly differentiated gastric cancer, but no hybridization was detected in normal epithelial cells adjacent to well‐differentiated gastric cancer. These findings may provide new information on HMG‐I mRNA expression in human gastrointestinal cancer and suggest a correlation between FMI mRNA expression to the differentiation and the stage of human gastrointestinal adenocarcinomas. Int. J. Cancer 74:1–6.

Alteration of immunoreactivity by hydrated autoclaving, microwave treatment, and simple heating of paraffin‐embedded tissue sections

The effects of treatment in a hydrated autoclave (121 °C, 2 atm for 20 min), microwave oven (in water), and simple heating (60 °C overnight in distilled water or 90 °C for 10 min in ZnSO4) on the stainability of 56 antigens by commercially available antibodies in formalin‐fixed paraffin‐embedded tissue sections were evaluated. The detectability of nuclear antigens, glycoprotein, lymphocytic surface markers, and chromogranin A was significantly and reproducibly improved by these treatments, whereas the detectability of viral antigens and peptide hormones was attenuated or unchanged. This enhancement includes not only the distinctiveness of the positive staining, but also the number of positive cells, as revealed by comparing serial sections. Among these four heating procedures, microwave heating and autoclaving were more effective than the others on p53, c‐erbB‐2, and CA125, whereas simple heating was best for smooth‐muscle actin (HHF35 and CGA7). Generally the effects of the heating procedures for these antigens were consistent among the cases, but the effects on GFAP varied with the case. The alterations we observed could significantly influence the interpretation of immunohistochemical staining of currently popular tumor markers such as p53 in terms of their prevalence (28%vs 64% in gastric cancer; 36%vs 82% in metastatic liver cancer) and other diagnostically important markers.

Allelic imbalances and homozygous deletion on 8p23.2 for stepwise progression of hepatocarcinogenesis

Early hepatocellular carcinoma (eHCC) originates from the hepatocytes of chronic liver disease and develops into classical hepatocellular carcinoma (HCC). To identify sequential genetic changes in multistep hepatocarcinogenesis, we analyzed molecular karyotypes using oligonucleotide genotyping 50K arrays. First, 1q21.3‐44 gain and loss of heterozygosity (LOH) on 1p36.21‐36.32 and 17p13.1‐13.3 were frequently observed in eHCC, but not in chronic liver diseases, suggesting that such chromosomal aberrations are early, possibly causative events in liver cancer. Next, we detected 25 chromosomal loci associated with liver cancer progression in five HCCs with nodule‐in‐nodule appearance, in which the inner nodule develops within eHCC lesion. Using these chromosomal regions as independent variables, decision tree analysis was applied on 14 early and 25 overt HCCs, and extracted combination of chromosomal gains on 5q11.1‐35.3 and 8q11.1‐24.3 and LOH on 4q11‐34.3 and 8p11.21‐23.3 as distinctive attributes, which can classify early and overt HCCs recursively. In these four altered regions identified as late events of hepatocarcinogenesis, two tumors in 32 overt HCCs analyzed in the present study and one in a set of independent samples of 36 overt HCCs in our previous study harbored a homozygous deletion near the CSMD1 locus on 8p23.2. CSMD1 messenger RNA expression was decreased in HCC without 8p23.2 deletion, possibly due to hypermethylation of the CpG islands in its promoter region. Conclusion: 1q gain and 1p and 17p LOH are early molecular events, whereas gains in 5q and 8q and LOH on 4q and 8p only occur in advanced HCC, and inactivation of the putative suppressor gene, CSMD1, may be the key event in progression of liver cancer. (HEPATOLOGY 2009.)

Human Sgo1 downregulation leads to chromosomal instability in colorectal cancer

Background and aims: Chromosomal instability (CIN) is recognised as a hallmark of cancer and is caused by a spindle assembly checkpoint disorder or chromosome mis-segregation during mitosis. Although the recent identification of human shugoshin (hSgo1), an important player in proper chromosome segregation, has suggested the involvement of hSgo1 in colorectal tumourigenesis, little is known about how it is involved. The aim of this study was to obtain information about the status of hSgo1 in human colorectal cancer. Method and results: Among the 46 colorectal cancer cases, hSgo1 mRNA expression was decreased in the tumour tissue in comparison with the corresponding normal tissue (p = 0.032). Human Sgo1-downregulated tumours (tumour to normal mucosa ratio<0.5) had preferential location on the left side large bowel rather than on the right side (p = 0.012), and a higher variation of centromere numbers revealed by fluorescence in situ hybridisation (FISH). To assess the effects of hSgo1 downregulation, hSgo1 knockdown was performed by transfecting the diploid HCT116 cell line with a short hairpin RNA expression vector. hSgo1 knockdown cells proliferated slowly because of both G2/M arrest and apoptosis (p<0.001), and markers of CIN in the form of aneuploidy (p<0.001) and micronuclei (p<0.005) were later observed in hSgo1 knockdown cells. Increased centrosome amplification (p<0.05), the presence of binucleated cells and mitotic catastrophes were also noted in hSgo1 knockdown cells. Conclusions: These findings suggest that hSgo1-downregulated colorectal cancers have a clinicopathological character of CIN, and hSgo1 downregulation leads to CIN in colorectal cancer cells.

Localization of Menkes gene expression in the mouse brain; its association with neurological manifestations in Menkes model mice

Abstract Menkes gene (Mc1 or MNK, encoding putative copper-transporting ATPase) expression was investigated and compared in normal and macular mutant mouse brain. Northern blot analysis showed a distinct 8.3-kb transcript and no obvious difference in size or extent in normal mice and macular mutants on postnatal days 0, 4, 7, 10 or 13. In situ hybridization revealed that certain specific populations of cells in the brain express Menkes mRNA, and that their localization in normal and mutant mice did not differ and was conserved on days 4, 10 and 13. The most intense hybridization signals were observed in the hippocampal CA1 region and dentate gyrus, the olfactory bulb nuclei, the cerebellar granular cell layer, the choroid plexus and the ependyma, with less intense signals in the hippocampal CA3 region and cerebellar Purkinje cells. In addition, necrotic neuronal cell death was predominantly observed in the CA3 region and the Purkinje cells of macular mice after postnatal day 10. The finding that the regions that had lower expression level of Menkes mRNA corresponded to those showing neuronal necrosis suggests that the Menkes gene may be responsible for the neuronal degeneration in some specific portions of the brain and clinical manifestations in this mutant.

Initial Intermittent Microwave Irradiation for Fluorescence In Situ Hybridization Analysis in Paraffin-Embedded Tissue Sections of Gastrointestinal Neoplasia

Initial Intermittent Microwave Irradiation for Fluorescence In Situ Hybridization Analysis in Paraffin-Embedded Tissue Sections of Gastrointestinal Neoplasia