A mortality gene(s) for the human adenocarcinoma line HeLa maps to a 130-kb region of human chromosome 4q22-q23

Replicative senescence-associated gene expression changes in mesenchymal stromal cells are similar under different culture conditions

BACKGROUND

Research on mesenchymal stromal cells has created high expectations for a variety of therapeutic applications. Extensive propagation to yield enough mesenchymal stromal cells for therapy may result in replicative senescence and thus hamper long-term functionality in vivo. Highly variable proliferation rates of mesenchymal stromal cells in the course of long-term expansions under varying culture conditions may already indicate different propensity for cellular senescence. We hypothesized that senescence-associated regulated genes differ in mesenchymal stromal cells propagated under different culture conditions.

DESIGN AND METHODS

Human bone marrow-derived mesenchymal stromal cells were cultured either by serial passaging or by a two-step protocol in three different growth conditions. Culture media were supplemented with either fetal bovine serum in varying concentrations or pooled human platelet lysate.

RESULTS

All mesenchymal stromal cell preparations revealed significant gene expression changes upon long-term culture. Especially genes involved in cell differentiation, apoptosis and cell death were up-regulated, whereas genes involved in mitosis and proliferation were down-regulated. Furthermore, overlapping senescence-associated gene expression changes were found in all mesenchymal stromal cell preparations.

CONCLUSIONS

Long-term cell growth induced similar gene expression changes in mesenchymal stromal cells independently of isolation and expansion conditions. In advance of therapeutic application, this panel of genes might offer a feasible approach to assessing mesenchymal stromal cell quality with regard to the state of replicative senescence.

Replicative senescence of mesenchymal stem cells: a continuous and organized process

Mesenchymal stem cells (MSC) comprise a promising tool for cellular therapy. These cells are usually culture expanded prior to their application. However, a precise molecular definition of MSC and the sequel of long-term in vitro culture are yet unknown. In this study, we have addressed the impact of replicative senescence on human MSC preparations. Within 43 to 77 days of cultivation (7 to 12 passages), MSC demonstrated morphological abnormalities, enlargement, attenuated expression of specific surface markers, and ultimately proliferation arrest. Adipogenic differentiation potential decreased whereas the propensity for osteogenic differentiation increased. mRNA expression profiling revealed a consistent pattern of alterations in the global gene expression signature of MSC at different passages. These changes are not restricted to later passages, but are continuously acquired with increasing passages. Genes involved in cell cycle, DNA replication and DNA repair are significantly down-regulated in late passages. Genes from chromosome 4q21 were over-represented among differentially regulated transcripts. Differential expression of 10 genes has been verified in independent donor samples as well as in MSC that were isolated under different culture conditions. Furthermore, miRNA expression profiling revealed an up-regulation of hsa-mir-371, hsa-mir-369-5P, hsa-mir-29c, hsa-mir-499 and hsa-let-7f upon in vitro propagation. Our studies indicate that replicative senescence of MSC preparations is a continuous process starting from the first passage onwards. This process includes far reaching alterations in phenotype, differentiation potential, global gene expression patterns, and miRNA profiles that need to be considered for therapeutic application of MSC preparations.

A region on human chromosome 4 (q35.1→qter) induces senescence in cell hybrids and is involved in cervical carcinogenesis

Human papillomavirus (HPV) types 16 and 18 are known to play a major role in cervical carcinogenesis. Additional genetic alterations are required for the development and progression of cervical cancer. Previously, we showed that the introduction of an entire human chromosome 4 into HPV-immortalized cells by microcell-mediated chromosome transfer (MMCT) can induce senescence in cell hybrids. In the present study, we established eight new murine donor cell lines harboring different fragments of the human chromosome 4. These were tested for their ability to induce senescence by MMCT into HPV16-immortalized keratinocytes (HPK II) and cervical carcinoma cells (HeLa). By exclusion, we could identify a region for a putative senescence gene or genes at 4q35.1-->qter. Further evidence that this locus may be involved in cervical carcinogenesis was obtained by studying sections of high-grade cervical intraepithelial neoplasias (CIN2/3) and cervical cancers from 87 women using a combination of interphase fluorescence in situ hybridization (I-FISH) and microsatellite PCR. I-FISH indicated copy number loss at 4q34-->qter. Microsatellite analysis showed that loss of one or more alleles at chromosome 4 was more frequent in the cervical carcinomas than in the CINs. Loss of heterozygosity (LOH) affected four areas, D4S412 (4p16.3), D4S2394 (4q28.2), D4S3041 (4q32.3), and D4S408 (4q35.1), and was highest at D4S408. LOH at terminal 4q has been reported previously for cervical carcinomas and other human malignancies. This is the first report associating allelic loss at 4q34-->qter with high-grade intraepithelial neoplasia and cervical carcinoma, and the first experimental evidence that this locus or these loci can induce senescence in cervical carcinoma cells and HPV16-immortalized cells.

Characterization of a conserved aphidicolin-sensitive common fragile site at human 4q22 and mouse 6C1: possible association with an inherited disease and cancer

Fragile sites are classified as common or rare depending on their occurrence in the populations. While rare sites are mainly associated with inherited diseases, common sites have been involved in somatic rearrangements found in the chromosomes of cancer cells. Here we study a mouse locus containing the ionotropic glutamate receptor delta 2 (grid2) gene in which spontaneous chromosome rearrangements occur frequently, giving rise to mutant animals in inbred populations. We identify and clone common fragile sites overlapping the mouse grid2 gene and its human ortholog GRID2, lying respectively at bands 6C1 and 4q22 in a 7-Mb-long region of synteny. These results show a third example of orthologous common sites conserved at the molecular level, and reveal an unexpected link between an inherited disease and an aphidicolin-sensitive region. Recurrent deletions of subregions of band 4q22 have been previously described in human hepatocellular carcinomas. This 15-Mb-long region appears precisely centered on the site described here, which strongly suggests that it also plays a specific role in hepatic carcinogenesis.