AURKA is one of the downstream targets of MAPK1/ERK2 in pancreatic cancer.

DUSP6/MKP-3, a specific inhibitor of MAPK1/ERK2, frequently loses its expression in primary pancreatic cancer tissues. This evidence suggests that constitutive activation of MAPK1 synergistically induced by frequent mutation of KRAS2 and the loss of function of DUSP6 plays key roles in pancreatic carcinogenesis and progression. By profiling of gene expressions associated with downregulation of MAPK1 induced by exogenous overexpression of DUSP6 in pancreatic cancer cells, we found that AURKA/STK15, the gene encoding Aurora-A kinase, which plays key roles in cellular mitosis, was among the downregulated genes along with its related genes, which included AURKB, TPX2 and CENPA. An association of expression and promoter activity of AURKA with MAPK activity was verified. Knockdown of ETS2 resulted in a reduction of AURKA expression. These results indicate that AURKA is a direct target of the MAPK pathway and that its overexpression in pancreatic cancer is induced by hyperactivation of the pathway, at least via ETS2.

Deletion mapping of 14q32 in human neuroblastoma defines an 1,100-kb region of common allelic loss.

BACKGROUND: We analyzed loss of heterozygosity (LOH) in 54 primary neuroblastomas (NBs) using 12 microsatellite markers on 14q32, and found that 31% (17/54) NBs showed LOH. PROCEDURE: The smallest region of overlap (SRO) was identified between D14S62 and D14S987. RESULTS: There was no statistical correlation between LOH and any clinicopathologic features, including age, stage, amplification of MYCN, and ploidy. A sequence-ready bacterial artificial chromosome (BAC) contig was constructed, and the minimum tiling path of six BACs covered the SRO; the physical length of this region was no larger than 1,000 kb. CONCLUSIONS: Our findings support the existence of a putative tumor-related gene on 14q32 for the tumorigenesis of NB.

Detailed deletion mapping of chromosome band 14q32 in human neuroblastoma defines a 1.1-Mb region of common allelic loss.

Neuroblastoma (NB) is a well-known malignant disease in infants, but its molecular mechanisms have not yet been fully elucidated. To investigate the genetic contribution of abnormalities on the long arm of chromosome 14 (14q) in NB, we analysed loss of heterozygosity (LOH) in 54 primary NB samples using 12 microsatellite markers on 14q32. Seventeen (31%) of 54 tumours showed LOH at one or more of the markers analysed, and the smallest common region of allelic loss was identified between D14S62 and D14S987. This region was estimated to be 1-cM long from the linkage map. Fluorescence in situ hybridization also confirmed the loss. There was no statistical correlation between LOH and any clinicopathologic features, including age, stage, amplification of MYCN and ploidy. We further constructed a contig spanning the lost region using bacterial artificial chromosome and estimated this region to be approximately 1.1-Mb by pulsed-field gel electrophoresis. Our results will contribute to cloning and characterizing the putative tumour-associated gene(s) in 14q32 in NB.

Expression of the DMBT1 gene is frequently suppressed in human lung cancer.

DMBT1 (deleted in malignant brain tumors) is a candidate tumor suppressor gene that has been mapped to chromosome 10q25.3-q26.1, a region in which frequent loss of heterozygosity (LOH) has been observed in several human tumors. Since DMBT1 is highly expressed in the lung, we analyzed LOH at the DMBT1 locus and expression of this gene in lung cancer. Thirty-five (53%) of 66 primary lung cancers showed LOH, and diminished expression of DMBT1 was observed in 20 (91%) of 22 lung cancer cell lines: three (14%) of them showed loss of expression. We further determined the primary structure of DMBT1 and analyzed genetic alterations in this gene using 23 lung cancer cell lines. Two (9%) of them had homozygous deletion within the gene, and two cell lines had genetic aberrations: one was a rearrangement involving exons 5 and 6, and the other was a missense mutation at codon 52. These results suggest that inactivation of the DMBT1 gene plays an important role in human lung carcinogenesis.

Identification of a 100-kb region of common allelic loss on chromosome bands 10q25-q26 in human endometrial cancer.

In human endometrial cancer, we have previously identified a 790-kb region of common allelic loss in chromosome bands 10q25-q26, flanked by D10S587 and D10S1723. We constructed a contig covering the entire deleted region using YACs, PACs, and BACs. Five overlapping cosmid clones derived from YAC clones completely covered the entire deleted region: its size was estimated to be no larger than 200 kb. We further performed two-color fluorescence in situ hybridization (FISH) analysis to confirm the deletion and narrowed down the deleted region to 100 kb or less; it was covered by three overlapping cosmid clones that were included in one BAC clone. Restriction endonuclease mapping identified a region in which NotI, SalI, SmaI, and Xhol were clustered, suggesting the possible existence of a CpG island.

The insulin-like growth factor II receptor gene is mutated in genetically unstable cancers of the endometrium, stomach, and colorectum.

Disruption of the DNA mismatch repair system, characterized by microsatellite instability (MI), plays an important role in the course of human carcinogenesis. Repetitive sequences constitute targets for mutation in MI+ cells, and frequent mutations have indeed been reported in such regions within the transforming growth factor beta receptor II (RII) gene in genetically unstable colorectal and gastric cancers. However, other genes that are targets for mutations in MI+ cells during the course of carcinogenesis have proven elusive. Because the insulin-like growth factor II receptor (IGFIIR) gene contains several repetitive sequences within its coding region, we examined mutations of this gene in MI+ cancers occurring at various primary sites. We found frameshift mutations in the poly(G)8 tract of IGFIIR in eight tumors, all of which were MI+: 4 of 26 (15%) MI+ endometrial cancers, 3 of 12 (25%) MI+ gastric cancers, and 1 of 18 (6%) MI+ colorectal cancers. In contrast, no mutation was found in 51 pancreatic cancers, 7 of which (14%) were MI+. These results implicate abnormal IGFIIR-mediated growth control in carcinogenesis involving the endometrium, stomach, and colorectum but not the pancreas.

Alternative splicing of GTBP in normal human tissues.

GTBP is one of the functional homologues of the bacterial mismatch repair gene mutS, whose product forms a heterodimer with hMSH2 to bind to the mismatched region of double-stranded DNA. We determined the expression of the GTBP gene and found that two forms of the transcripts were ubiquitously expressed in normal human tissues. These transcripts, termed GTBP-N and GTBP-ALT, were generated by the alternative splicing machinery. These two transcripts share 3172 bp from the translation initiation codon that codes for 1057 amino acids. GTBP-ALT lacked a region that codes for a highly conserved region between GTBP-N, hMSH2, and hMSH3 in their C-termini.