p53 status in multiple human urothelial cancers: assessment for clonality by the yeast p53 functional assay in combination with p53 immunohistochemistry

High frequency of temperature-sensitive mutants of p53 in glioblastoma

Glioblastoma is the most common and the most aggressive type of brain cancer. Aberrations of the RTK/RAS/PI3K-, p53-, and RB cell signaling pathways were recognized as a core requirement for pathogenesis of glioblastoma. The p53 tumor suppressor functions as a transcription factor transactivating expression of its target genes in response to various stress stimuli. We determined the p53 status in 36 samples of glioblastoma by functional analyses FASAY and split assay. Seventeen p53 mutations were detected and further analyzed by cDNA and gDNA sequencing in 17 patients (47.2 %). Fifteen (88.2 %) of the mutations were missense mutations causing amino acid substitutions, seven of them exhibited temperature-sensitivity. Two mutations were determined as short deletions, one of them causing formation of premature termination codon in position 247. Fluorescent in situ hybridization revealed the loss of the p53-specific 17p13.3 locus in four of 33 analyzed samples (12 %). In 12 out of 30 samples (40 %), the p53 protein accumulation was shown by immunoblotting. There was high (80 %) concordance between the presence of the clonal p53 mutation and the p53 protein accumulation.

Origin of multifocal carcinomas of the bladder and upper urinary tract: molecular analysis and clinical implications

The simultaneous or metachronous development of multifocal tumors with identical or variable histological features in the urothelial tract in a single patient is a well-known characteristic of urothelial cancer. To explain this phenomenon, two distinct concepts have been proposed: the 'field defect' hypothesis according to which urothelial cells in patients are primed to undergo transformation by previous carcinogenic insults and the 'single progenitor cell' hypothesis, which asserts that the multifocal development is caused by the seeding or intraepithelial spread of transformed cells. Results of recent molecular genetic studies support the 'single progenitor cell' hypothesis, and indicate that the genetic and phenotypic diversity observed in multifocal urothelial tumors is a consequence of clonal evolution from a single transformed cell. An understanding of the mechanism of the heterotopic recurrence of urothelial cancer may provide new prospects for early molecular detection and prevention of heterotopic recurrence of urothelial cancer.

p53 and H-ras mutations and microsatellite instability in renal pelvic carcinomas of NON / Shi mice treated with N-butyl-N-(4-hydroxybutyl)-nitrosamine: different genetic alteration from urinary bladder carcinoma

We previously reported p53 mutations to be frequent (greater than 70%), whereas both H-ras mutations and microsatellite instability (MSI) were infrequent (about 10%), in urinary bladder carcinomas (UBCs) and their metastatic foci in the N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN)-induced mouse urothelial carcinogenesis model. In the present study, an analysis of p53 and H-ras mutations as well as MSI was performed on 12 renal pelvic carcinomas (RPCs) and 8 metastatic or invading foci produced by the same experimental procedure. Histologically, 10 of the RPCs were transitional cell carcinomas and the remaining 2 were squamous cell carcinomas. p53 mutations were infrequent and only found in one primary RPC (8%), its metastatic foci and an invading lesion in another animal (in a total 2 of 12; 17%). H-ras mutations were slightly more frequent (found in 3 of 12 animals; 25%), 4 of 5 involving codon 44, GTG to GCG, not a hot-spot reported for human cancers. In two cases, H-ras mutations were confined to lung metastasis and not detectable in their primary RPCs. MSI analysis was available for 6 pairs of primary RPCs and their metastatic foci, and 4 animals (67%) had MSI at one or more microsatellite loci. Overall, the distribution of genetic alterations differed from that in UBCs produced by the same experimental protocol. The results thus suggest that different genetic pathways may participate in carcinogenesis of the upper and lower urinary tract due to BBN.

Isolation of differentiated squamous and undifferentiated spindle carcinoma cell lines with differing metastatic potential from a 4-nitroquinoline N-Oxide-induced tongue carcinoma in a F344 rat

One differentiated squamous cell carcinoma (SCC) cell line (RSC3-E2) and two undifferentiated tumor cell lines (RSC3-LM and RSC3-E2R) with different metastatic potential were established from a 4-nitroquinoline N-oxide (4NQO)-induced differentiated SCC in F344 rat tongue. The RSC3-E2 subline was isolated from a parental cell line (RSC3-P) by single cell cloning in vitro, whereas the RSC3-LM subline was isolated from a lung metastatic focus after subcutaneous (s.c.) injection of RSC3-P cells. The RSC3-E2R cell line was isolated from a lung metastatic focus following s.c. injection of RSC3-E2 cells after X-irradiation in vitro. The RSC3-E2 cell line is keratin-positive and grows as a keratinizing tumor in nude mice, whereas RSC3-LM and RSC3-E2R cells are keratin-negative, vimentin-positive and form undifferentiated tumors. When s.c. injected into nude mice, the RSC3-E2 cell line proved to be non-metastatic, while the RSC3-LM cell line was metastatic by both hematogenous and lymphogenous routes, and the RSC3-E2R cell line was metastatic only hematogenously. In vitro relative growth rates and in vitro invasion activity of these cell lines were in the order RSC3-LM > RSC3-E2R > RSC3-E2. Chromosome analysis revealed two peaks with modal chromosome numbers of 83 and 78 for RSC3-P cells and single peaks at 83, 78 and 56 for RSC3-LM, RSC3-E2 and RSC3-E2R cell lines, respectively. Common structural abnormalities on chromosome 11 were shared by all cell lines. Mutation analysis of the p53 gene using a yeast functional assay demonstrated RSC3-LM cell line to have a point mutation at codon 269, whereas RSC3-E2 and RSC3-E2R had double mutations at codons 106 and 170 on each allele. These results suggest that the two undifferentiated RSC3-LM and RSC3-E2R tumor cell lines with different metastatic potential were generated from differentiated SCC cells via different genetic pathways as a consequence of tumor progression in vivo and in vitro, respectively. These cell lines should provide a useful model for understanding mechanisms of hematogenous and lymphogenous metastasis, as well as tumor progression of oral SCCs.