Identification of tumor metastasis suppressor region on the short arm of human chromosome 20

Candidate metastasis suppressor genes uncovered by array comparative genomic hybridization in a mouse allograft model of prostate cancer

Background

The purpose of this study was to identify candidate metastasis suppressor genes from a mouse allograft model of prostate cancer (NE-10). This allograft model originally developed metastases by twelve weeks after implantation in male athymic nude mice, but lost the ability to metastasize after a number of in vivo passages. We performed high resolution array comparative genomic hybridization on the metastasizing and non-metastasizing allografts to identify chromosome imbalances that differed between the two groups of tumors.

Results

This analysis uncovered a deletion on chromosome 2 that differed between the metastasizing and non-metastasizing tumors. Bioinformatics filters were employed to mine this region of the genome for candidate metastasis suppressor genes. Of the 146 known genes that reside within the region of interest on mouse chromosome 2, four candidate metastasis suppressor genes (Slc27a2, Mall, Snrpb, and Rassf2) were identified. Quantitative expression analysis confirmed decreased expression of these genes in the metastasizing compared to non-metastasizing tumors.

Conclusion

This study presents combined genomics and bioinformatics approaches for identifying potential metastasis suppressor genes. The genes identified here are candidates for further studies to determine their functional role in inhibiting metastases in the NE-10 allograft model and human prostate cancer.

Differentially expressed genes in the prostate cancer cell line LNCaP after exposure to androgen and anti-androgen

Androgens play an important role in growth and maintenance of prostate cells. The actions of androgens are mediated by the androgen receptor (AR), a transcription factor member of the super-family of nuclear hormone receptors. Androgen regulated genes (ARGs) are potential markers for early diagnosis and treatment of prostate cancer patients. In the present study, we used DDRT-PCR (differential display reverse transcriptase polymerase chain reaction) technique in order to investigate differentially expressed genes in the prostate cancer cell line LNCaP after treatment with dihydrotestosterone and bicalutamide for 6, 24, and 48 hours. Fifty-five differentially expressed fragments were isolated, cloned, and sequenced. Sequencing analysis of these fragments revealed 56 different transcripts that showed homology to transcription factors, cell cycle regulators, metabolic enzymes, and hypothetical proteins. Among the differentially expressed genes, SPA17 and DDEF2 were further validated using quantitative real time RT-PCR (qPCR) in a series of 25 prostate tumor samples. The DDEF2 gene is involved in adhesion and cell migration of monocytes, and the SPA17 gene might be involved in cellular signal transduction. The transcripts of both, SPA17 and DDEF2 genes, showed altered pattern of expression in the group of prostate tumors analyzed by qPCR. The differentially expressed genes identified in this study might provide new insights into the androgen signaling pathways in prostate cells.

The manipulation of chromosomes by mankind: the uses of microcell-mediated chromosome transfer

Microcell-mediated chromosome transfer (MMCT) was a technique originally developed in the 1970s to transfer exogenous chromosome material into host cells. Although, the methodology has not changed considerably since this time it is being used to great success in progressing several different fields in modern day biology. MMCT is being employed by groups all over the world to hunt for tumour suppressor genes associated with specific cancers, DNA repair genes, senescence-inducing genes and telomerase suppression genes. Some of these genomic discoveries are being investigated as potential treatments for cancer. Other fields have taken advantage of MMCT, and these include assessing genomic stability, genomic imprinting, chromatin modification and structure and spatial genome organisation. MMCT has also been a very useful method in construction and manipulation of artificial chromosomes for potential gene therapies. Indeed, MMCT is used to transfer mainly fragmented mini-chromosome between cell types and into embryonic stem cells for the construction of transgenic animals. This review briefly discusses these various uses and some of the consequences and advancements made by different fields utilising MMCT technology.

Chromosome 18 suppresses tumorigenic properties of human prostate cancer cells

Although prostate cancer is still the most diagnosed cancer in men, most genes implicated in its progression are yet to be identified. Chromosome abnormalities have been detected in human prostate tumors, many of them associated with prostate cancer progression. Indeed, alterations (including deletions or amplifications) of more than 15 human chromosomes have been reported in prostate cancer. We hypothesized that transferring normal human chromosomes into human prostate cancer cells would interfere with their tumorigenic and/or metastatic properties. We used microcell-mediated chromosome transfer to introduce human chromosomes 10, 12, 17, and 18 into highly tumorigenic (PC-3M-Pro4) and highly metastatic (PC-3M-LN4) PC-3-derived cell lines. We tested the in vitro and in vivo properties of these hybrids. Introducing chromosome 18 into the PC-3M-LN4 prostate cancer cell line greatly reduced its tumorigenic phenotype. We observed retarded growth in soft agar, decreased invasiveness through Matrigel, and delayed tumor growth into nude mice, both subcutaneously and orthotopically. This phenotype is associated with a marker in the 18q21 region. Combined with the loss of human chromosome 18 regions often seen in patients with advanced prostate cancer, our results show that chromosome 18 encodes one or more tumor-suppressor genes whose inactivation contributes to prostate cancer progression.

Chromosome 18 suppresses prostate cancer metastases

Loss of heterozygosity and allelic imbalance data has shown that there are two distinct regions of loss on chromosome 18q associated with the progression of prostate cancer (CaP). To investigate the functional significance of chromosome 18q loci in CaP, we utilized the technique of microcell-mediated chromosome transfer to introduce an intact chromosome 18 into the human prostate cancer cell line, PC-3. Three of the resulting hybrid lines were compared to the PC-3 cells in vitro and in vivo. The hybrid cell lines, containing an intact copy of the introduced chromosome 18, exhibited a substantial reduction in anchorage-dependent and independent growth in vitro. These hybrid cell lines also made smaller tumors in nude mice following subcutaneous injection compared to PC-3 cells. Because tumor growth was not completely eliminated by introduction of chromosome 18, we assessed the ability of the hybrids to metastasize to bone after intra-cardiac inoculation in a nude mouse model. Mice inoculated with PC-3 hybrids containing intact copies of chromosome 18 had significantly fewer bone metastases and dramatically improved survival compared to PC-3 cells. In addition, the introduction of chromosome 18 significantly reduced tumor burden in extraskeletal sites. This was not because of differences in growth rates because mice bearing hybrids were monitored for metastases over twice as long as mice bearing PC-3 cells. Taken together, these data suggest that chromosome 18 has a functional role in CaP to suppress growth and metastases. Identification of the responsible gene(s) may lead to molecular targets for drug discovery.

The microcell mediated transfer of human chromosome 8 into highly metastatic rat liver cancer cell line C5F

AIM: Our previous research on the surgical samples of primary liver cancer with CGH showed that the loss of human chromosome 8p had correlation with the metastatic phenotype of liver cancer. In order to seek the functional evidence that there could be a metastatsis suppressor gene (s) for liver cancer on human chromosome 8, we tried to transfer normal human chromosome 8 into rat liver cancer cell line C5F, which had high metastatic potential to lung.

METHODS: Human chromosome 8 randomly marked with neo gene was introduced into C5F cell line by MMCT and positive microcell hybrids were screened by double selections of G418 and HAT. Single cell isolation cloning was applied to clone microcell hybrids. Finally, STS-PCR and WCP-FISH were used to confirm the introduction.

RESULTS: Microcell hybrids resistant to HAT and G418 were obtained and 15 clones were obtained by single-cell isolation cloning. STS-PCR and WCP-FISH proved that human chromosome 8 had been successfully introduced into rat liver cancer cell line C5F. STS-PCR detected a random loss in the chromosome introduced and WCP-FISH found a consistent recombination of the introduced human chromosome with the rat chromosome.

CONCLUSION: The successful introduction of human chromosome 8 into highly metastatic rat liver cancer cell line builds the basis for seeking functional evidence of a metastasis suppressor gene for liver cancer harboring on human chromosome 8 and its subsequent cloning.

Multiple human chromosomes carrying tumor-suppressor functions for the mouse melanoma cell line B16-F10, identified by microcell-mediated chromosome transfer

Many tumor-suppressor genes are involved in the development and progression of cellular malignancy. To understand the functional role of tumor-suppressor genes in melanoma and to identify the human chromosome that carries these genes, we transferred individually each normal human chromosome, except for the Y chromosome, into the mouse melanoma cell line B16-F10, by microcell fusion. We examined the tumorigenicity of hybrid cells in nude mice and their in vitro growth properties. The introduction of human chromosomes 1 and 2 elicited a remarkable change in cell morphologic features, and cellular senescence was induced at seven to 10 population doublings. The growth rates of tumors derived from microcell hybrid clones containing introduced human chromosome 5, 7, 9, 10, 11, 13, 14, 15, 16, 19, 20, 21, 22, or X were significantly slower than that of the parental B16-F10 cells, whereas the introduction of other human chromosomes had no effect on the tumorigenicity of these cells. The majority of microcell hybrid clones that exhibited suppressed tumorigenicity also showed a moderate reduction in doubling time compared with B16-F10 cells. Microcell hybrid clones with an introduced human chromosome 5 showed complete suppression of in vitro-transformed phenotypes, including cell growth, saturation density, and colony-forming efficiency in soft agar. Thus, these results indicated the presence of many cell senescence-related genes and putative tumor-suppressor genes for the mouse melanoma cell line B16-F10 and showed in vitro that many tumor-suppressor genes control the phenotypes of transformed cells in the multistep process of neoplastic development.