A human melanoma metastasis-suppressor locus maps to 6q16.3-q23

KISS-1, Mediated by Promoter Methylation, Suppresses Esophageal Squamous Cell Carcinoma Metastasis via MMP2/9/MAPK Axis

BACKGROUND AND AIMS

KISS-1 is an established tumor suppressor that inhibits metastases in various malignancies. However, little is known regarding its role in esophageal squamous cell carcinoma (ESCC). The aim of the present study was to identify the possible mechanisms of KISS-1 in ESCC metastasis.

METHODS

The expression levels of KISS-1 mRNA and protein in ESCC samples and cell lines were analyzed by qRT-PCR, IHC, and western blotting. Bisulfite sequencing PCR (BSP) and methylation-specific PCR (MSP) were used to analyze the methylation pattern of KISS-1 promoter in ESCC cells with or without 5-Aza-dC treatment. The role of KISS-1 in the progression and metastasis of ESCC was analyzed through in vitro functional assays.

RESULTS

KISS-1 mRNA and protein were markedly downregulated in ESCC tissues and cell lines compared to the respective controls. Hypermethylation of KISS-1 promoter correlated to its lower expression levels in ESCC, and KISS-1 demethylation inhibited tumor progression. Ectopic KISS-1 overexpression inhibited tumor cell metastasis in vitro. In addition, KISS-1 overexpression downregulated the matrix metalloproteinase 2 and 9 (MMP2 and 9) and inhibited epithelial-mesenchymal transition (EMT). Finally, KISS-1 downregulated phosphorylated extracellular regulated protein kinase 1/2 (ERK1/2) and phosphorylated p38 mitogen-activated protein kinase (MAPK) without affecting their total expression levels in the ESCC cells. MAPK/ERK and p38 MAPK agonists reversed the suppressive effects of KISS-1.

CONCLUSIONS

The hypermethylation of KISS-1 promoter partly contributed to its downregulation in ESCC. KISS-1 inhibits the metastasis of ESCC cells by targeting the MMP2/9/ERK/p38 MAPK axis.

Nuclear Receptor Coactivator NCOA3 Regulates UV Radiation-Induced DNA Damage and Melanoma Susceptibility

Melanoma occurs as a consequence of inherited susceptibility to the disease and exposure to UV radiation (UVR) and is characterized by uncontrolled cellular proliferation and a high mutational load. The precise mechanisms by which UVR contributes to the development of melanoma remain poorly understood. Here we show that activation of nuclear receptor coactivator 3 (NCOA3) promotes melanomagenesis through regulation of UVR sensitivity, cell-cycle progression, and circumvention of the DNA damage response (DDR). Downregulation of NCOA3 expression, either by genetic silencing or small-molecule inhibition, significantly suppressed melanoma proliferation in melanoma cell lines and patient-derived xenografts. NCOA3 silencing suppressed expression of xeroderma pigmentosum C and increased melanoma cell sensitivity to UVR. Suppression of NCOA3 expression led to activation of DDR effectors and reduced expression of cyclin B1, resulting in G₂-M arrest and mitotic catastrophe. A SNP in NCOA3 (T960T) reduced NCOA3 protein expression and was associated with decreased melanoma risk, given a significantly lower prevalence in a familial melanoma cohort than in a control cohort without cancer. Overexpression of wild-type NCOA3 promoted melanocyte survival following UVR and was accompanied by increased levels of UVR-induced DNA damage, both of which were attenuated by overexpression of NCOA3 (T960T). These results describe NCOA3-regulated pathways by which melanoma can develop, with germline NCOA3 polymorphisms enabling enhanced melanocyte survival in the setting of UVR exposure, despite an increased mutational burden. They also identify NCOA3 as a novel therapeutic target for melanoma. SIGNIFICANCE: This study explores NCOA3 as a regulator of the DDR and a therapeutic target in melanoma, where activation of NCOA3 contributes to melanoma development following exposure to ultraviolet light.

KISS1 in breast cancer progression and autophagy

Tumor suppressors are cellular proteins typically expressed in normal (non-cancer) cells that not only regulate such cellular functions as proliferation, migration and adhesion, but can also be secreted into extracellular space and serve as biomarkers for pathological conditions or tumor progression. KISS1, a precursor for several shorter peptides, known as metastin (Kisspeptin-54), Kisspeptin-14, Kisspeptin-13 and Kisspeptin-10, is one of those metastasis suppressor proteins, whose expression is commonly downregulated in the metastatic tumors of various origins. The commonly accepted role of KISS1 in metastatic tumor progression mechanism is the ability of this protein to suppress colonization of disseminated cancer cells in distant organs critical for the formation of the secondary tumor foci. Besides, recent evidence suggests involvement of KISS1 in the mechanisms of tumor angiogenesis, autophagy and apoptosis regulation, suggesting a possible role in both restricting and promoting cancer cell invasion. Here, we discuss the role of KISS1 in regulating metastases, the link between KISS1 expression and the autophagy-related biology of cancer cells and the perspectives of using KISS1 as a potential diagnostic marker for cancer progression as well as a new anti-cancer therapeutics.

Multiple biological functions of transcription factor 21 in the development of various cancers

Transcription factor 21 (TCF21) is a basic helix–loop–helix transcription factor that binds to DNA and regulates cell differentiation and cell fate specification through mesenchymal–epithelial transition during development. The TCF21 gene is epigenetically inactivated in many types of human cancers and exerts a wide variety of functions, including the regulation of epithelial–mesenchymal transition, invasion, metastasis, cell cycle, and autophagy. This review focuses on research progress in relation to the roles of TCF21 in tumor development. We systematically consider multiple pathological functions of TCF21 in various cancers, revealing the molecular bases of its diverse biological roles and providing new directions for future research.

Controversial Role of Kisspeptins/KiSS-1R Signaling System in Tumor Development

KiSS-1 was first described as a metastasis suppressor gene in malignant melanoma. KiSS-1 encodes a 145 amino-acid residue peptide that is further processed, producing the 54 amino acid metastin and shorter peptides collectively named kisspeptins (KPs). KPs bind and activate KiSS-1R (GPR54). Although the KPs system has been extensively studied for its role in endocrinology of reproductive axis in mammals, its role in cancer is still controversial. Experimental evidences show that KP system exerts an anti-metastatic effect by the regulation of cellular migration and invasion in several cancer types. However, the role of KPs/KiSS-1R is very complex. Genomic studies suggest that KiSS-1/KiSS-1R expression might be different in the various stages of tumor development. Furthermore, overexpression of KiSS-1R has been reported to elicit drug resistance in triple negative breast cancer. In this review, we focused on multiple functions exerted by the KPs/KiSS-1R system in regulating tumor progression.

Concurrence of chromosome 6 chromothripsis and glioblastoma metastasis

The authors report an unusual case of a widely metastatic glioblastoma. DNA copy number microarray profile of the resected specimen revealed complex rearrangements found throughout chromosome 6, a phenomenon known as chromothripsis. Such chromothripsis pattern was not observed in 50 nonmetastatic glioblastoma specimens analyzed. Analysis of the 1000+ gliomas profiled by The Cancer Genome Atlas (TCGA) data set revealed one case of chromosome 6 chromothripsis resembling the case described here. This TCGA patient died within 6 months of undergoing tumor resection. Implications of these findings are reviewed in the context of the current literature.

The Kiss-1/Kiss-1R complex as a negative regulator of cell motility and cancer metastasis (Review)

Metastasis is a complex multistep process that involves the impairment of cell-cell adhesion in the neoplastic epithelium, invasion into adjacent tissues and the dissemination of cancer cells through the lymphatic and haematogenous routes. The inhibition of the metastatic process at an early stage has become a hot topic in cancer research. The Kiss-1 gene, initially described as a suppressor of metastasis in malignant melanoma, encodes the Kiss-1 protein which can be processed to other peptides, e.g., Kisspeptin-10, Kisspeptin-13, Kisspeptin-14 and Kisspeptin-54. These peptides are endogenous ligands of the Kiss‑1 receptor (Kiss-1R), a G protein-coupled receptor (GPR) also known as hOT7T175, AXOR12 or GPR54. The Kiss-1 gene has been suggested as a suppressor of metastasis in a various types of cancer, including gastric cancer, oesophageal carcinoma, pancreatic, ovarian, bladder and prostate cancer, through the regulation of cellular migration and invasion. In the current review, we summarise the current understanding of the role of Kiss‑1 and Kiss‑1R in cancer and cancer metastasis.

RTN4IP1 is down-regulated in thyroid cancer and has tumor-suppressive function

CONTEXT

Previously we identified RTN4IP1 to be differentially expressed in thyroid cancer by sex and the gene is located on chromosome 6q21, a chromosomal region frequently deleted or with loss of heterozygosity in a variety of human malignancies including thyroid cancer.

OBJECTIVE

Because the expression and function of this gene is unknown, we sought to characterize its expression in normal, hyperplastic, and benign and malignant thyroid tissue samples and to evaluate its function in cancer cells.

DESIGN

RTN4IP1 expression was analyzed in normal and hyperplastic thyroid tissue and benign and malignant thyroid tissue samples. In 3 thyroid cancer cell lines (TPC1 from a papillary thyroid cancer, FTC133 from a follicular thyroid cancer, XTC1 from a Hürthle cell carcinoma), small interfering RNA knockdown of RTN4IP1 was used to determine its role in regulating the hallmarks of malignant cell phenotype (cellular proliferation, migration, apoptosis, invasion, tumor spheroid formation, anchorage independent growth).

RESULTS

We found RTN4IP1 mRNA expression was significantly down-regulated in follicular and papillary thyroid cancer as compared with normal, hyperplastic, and benign thyroid neoplasms (P < .05). Moreover, RTN4IP1 mRNA expression was significantly lower in larger papillary thyroid cancers (P < .05). Small interfering RNA knockdown of RTN4IP1 expression increased cellular proliferation (2- to 4-fold) in all 3 of the cell lines tested and increased cellular invasion (1.5- to 3-fold) and migration (2- to 7.5-fold), colony formation (3- to 6-fold), and tumor spheroid formation (P < .05) in 2 of the 3 cell lines tested (FTC-133 and XTC1).

CONCLUSIONS

This is the first study to characterize the expression and function of RTN4IP1 in cancer. Our results demonstrate RTN4IP1 is down-regulated in thyroid cancer and is associated with larger papillary thyroid cancer and that it regulates malignant cell phenotype. These findings, taken together, suggest that RTN4IP1 has a tumor-suppressive function and may regulate thyroid cancer progression.

Antiproliferative effects of kisspeptin‑10 depend on artificial GPR54 (KISS1R) expression levels

Kisspeptins are peptides derived from the metastasis suppressor gene KISS1 interacting with GPR54 as their corresponding receptor. The KISS1/GPR54 system is one regulator of cellular motility mechanisms leading to decreased migration and invasion. Its role in cell proliferation processes is not clearly understood. In this study, breast cancer cell lines, T47D, ZR75-1, MDA‑MB‑231, MDA‑MB‑435s, MDA‑MB‑453, HCC 70, HCC 1806, HCC 1937 and MCF‑7, were investigated for their endogenous GPR54 expression by immunocytochemistry, RT‑PCR and western blot analysis. The effect of kisspeptin‑10 on proliferation was measured in MDA‑MB‑231, MDA‑MB‑435s, HCC 1806 and MCF‑7 cells. Further experiments on proliferation were carried out with cells transfected with GPR54. All of the tested breast cancer cell lines expressed GPR54 in different amounts. No effects on proliferation were detected in the breast cancer cells expressing the receptor endogenously. In transfected neuronal cells overexpressing GPR54, proliferation was significantly inhibited by kisspeptin‑10. The results indicate that the antiproliferative action of kisspeptin depends on the nature of GPR54 expression. The effect was detected in an artificial system of cells transfected with GPR54 and not in cells expressing the receptor endogenously. Thus, the antiproliferative action of kisspeptin seems not to be important for pathophysiological processes.

Pleckstrin homology domain-interacting protein (PHIP) as a marker and mediator of melanoma metastasis

Although melanomas with mutant v-Raf murine sarcoma viral oncogene homolog B1 (BRAF) can now be effectively targeted, there is no molecular target for most melanomas expressing wild-type BRAF. Here, we show that the activation of Pleckstrin homology domain-interacting protein (PHIP), promotes melanoma metastasis, can be used to classify a subset of primary melanomas, and is a prognostic biomarker for melanoma. Systemic, plasmid-based shRNA targeting of Phip inhibited the metastatic progression of melanoma, whereas stable suppression of Phip in melanoma cell lines suppressed metastatic potential and prolonged the survival of tumor-bearing mice. The human PHIP gene resides on 6q14.1, and although 6q loss has been observed in melanoma, the PHIP locus was preserved in melanoma cell lines and patient samples, and its overexpression was an independent adverse predictor of survival in melanoma patients. In addition, a high proportion of PHIP-overexpressing melanomas harbored increased PHIP copy number. PHIP-overexpressing melanomas include tumors with wild-type BRAF, neuroblastoma RAS viral (v-ras) oncogene homolog, and phosphatase and tensin homolog, demonstrating PHIP activation in triple-negative melanoma. These results describe previously unreported roles for PHIP in predicting and promoting melanoma metastasis, and in the molecular classification of melanoma.

GWAS findings for human iris patterns: associations with variants in genes that influence normal neuronal pattern development

Human iris patterns are highly variable. The origins of this variation are of interest in the study of iris-related eye diseases and forensics, as well as from an embryological developmental perspective, with regard to their possible relationship to fundamental processes of neurodevelopment. We have performed genome-wide association scans on four iris characteristics (crypt frequency, furrow contractions, presence of peripupillary pigmented ring, and number of nevi) in three Australian samples of European descent. Both the discovery (n = 2121) and replication (n = 499 and 73) samples showed evidence for association between (1) crypt frequency and variants in the axonal guidance gene SEMA3A (p = 6.6 × 10(-11)), (2) furrow contractions and variants within the cytoskeleton gene TRAF3IP1 (p = 2.3 × 10(-12)), and (3) the pigmented ring and variants in the well-known pigmentation gene SLC24A4 (p = 7.6 × 10(-21)). These replicated findings individually accounted for around 1.5%-3% of the variance for these iris characteristics. Because both SEMA3A and TRAFIP1 are implicated in pathways that control neurogenesis, neural migration, and synaptogenesis, we also examined the evidence of enhancement among such genes, finding enrichment for crypts and furrows. These findings suggest that genes involved in normal neuronal pattern development may also influence tissue structures in the human iris.

Epigenetic deregulation of TCF21 inhibits metastasis suppressor KISS1 in metastatic melanoma

Metastatic melanoma is a fatal disease due to the lack of successful therapies and biomarkers for early detection and its incidence has been increasing. Genetic studies have defined recurrent chromosomal aberrations, suggesting the location of either tumor suppressor genes or oncogenes. Transcription factor 21 (TCF21) belongs to the class A of the basic helix-loop-helix family with reported functions in early lung and kidney development as well as tumor suppressor function in the malignancies of the lung and head and neck. In this study, we combined quantitative DNA methylation analysis in patient biopsies and in their derived cell lines to demonstrate that TCF21 expression is downregulated in metastatic melanoma by promoter hypermethylation and TCF21 promoter DNA methylation is correlated with decreased survival in metastatic skin melanoma patients. In addition, the chromosomal location of TCF21 on 6q23-q24 coincides with the location of a postulated metastasis suppressor in melanoma. Functionally, TCF21 binds the promoter of the melanoma metastasis-suppressing gene, KiSS1, and enhances its gene expression through interaction with E12, a TCF3 isoform and with TCF12. Loss of TCF21 expression results in loss of KISS1 expression through loss of direct interaction of TCF21 at the KISS1 promoter. Finally, overexpression of TCF21 inhibits motility of C8161 melanoma cells. These data suggest that epigenetic downregulation of TCF21 is functionally involved in melanoma progression and that it may serve as a biomarker for aggressive tumor behavior.

International Union of Basic and Clinical Pharmacology. LXXVII. Kisspeptin receptor nomenclature, distribution, and function

Kisspeptins are members of the Arg-Phe amide family of peptides, which have been identified as endogenous ligands for a G-protein-coupled receptor encoded by a gene originally called GPR54 (also known as AXOR12 or hOT7T175). After this pairing, the gene has been renamed KISS1R. The International Union of Basic and Clinical Pharmacology Committee on Receptor Nomenclature and Drug Classification recommends that the official name for the receptor is the kisspeptin receptor to follow the convention of naming the receptor protein after the endogenous ligand. The endogenous ligand was initially called metastin, after its role as a metastasis suppressor, and is now referred to as kisspeptin-54 (KP-54), a C-terminally amidated 54-amino acid peptide cleaved from the 145-amino acid gene product. Shorter C-terminal cleavage fragments [KP-14, KP-13 and KP-10 (the smallest active fragment)] are also biologically active. Both receptor and peptide are widely expressed in human, rat, and mouse; the receptor sequence shares more than 80% homology in these species. Activation of the kisspeptin receptor by kisspeptin is via coupling to G(q/11) and the phospholipase C pathway, causing Ca(2+) mobilization. Mutations in the KISS1R gene result in hypogonadotropic hypogonadotropism, and targeted disruption of Kiss1r in mice reproduces this phenotype, which led to the discovery of the remarkable ability of the kisspeptin receptor to act as a molecular switch for puberty. In addition to regulating the reproductive axis, the kisspeptin receptor is also implicated in cancer, placentation, diabetes, and the cardiovascular system.

The KISS1 metastasis suppressor: a good night kiss for disseminated cancer cells

Re-expression of KISS1 in tumor cell lines allows all antecedent steps of metastasis, but prevents colonization of secondary sites. Because tumor cells have already disseminated by the time of cancer diagnosis, KISS1 may represent a new opportunity for therapeutic intervention. Moreover, numerous clinical reports demonstrate that a loss or reduction of KISS1 expression in different human cancers inversely correlates with tumor progression, metastasis, and survival. Taken together, these observations compel the hypothesis that KISS1 could be of tremendous utility in controlling metastasis in a therapeutic context. In this review, we highlight some key findings from preclinical and clinical studies and discuss strategies whereby KISS1 may be exploited clinically to treat metastases.

Allelotyping, microsatellite instability, and BRAF mutation analyses in common and atypical melanocytic nevi and primary cutaneous melanomas

Loss of heterozygosity (LOH) in several chromosomal regions is found in melanoma, and it has been partially studied in nevi. BRAF mutations are found in melanoma and nevi and in colorectal cancer are linked to mismatch repair deficiency. We studied early genetic events involved in melanomagenesis through analysis of allelic loss, microsatellite instability (MSI), and BRAF mutations. DNA extracted from microdissected cells of 22 common nevi, 23 atypical nevi, and 25 primary cutaneous melanomas were examined for LOH and MSI by polymerase chain reaction-based analysis of 24 microsatellite markers and BRAF mutation. Allelic loss index was higher in atypical nevi (0.20) and melanomas (0.27) than common nevi (0.07). LOH was frequent at 9p21, 17q21, 6q23, and 5q35 in melanoma. LOH at any of this loci occurred in 27% of common nevi, 57% of atypical nevi, and 68% of melanomas. BRAF mutations were not related to MSI presence and MSI index was not related with BRAF mutational status. Similar genetic alterations in atypical nevi and melanomas support the concept of atypical nevus as melanoma precursor. Novel deletion loci at 5q35 and 17q21 (BRCA1) in atypical nevi and melanomas were identified. Mismatch repair deficiency is not a crucial event for BRAF mutation in melanocytic tumors.

GPR54 and kisspeptins

The G-protein coupled receptor GPR54 has an essential role in the initiation and maintenance of mammalian fertility. Humans and mice with mutations in GPR54 have hypogonadotropic hypogonadism characterized by absence of sexual maturation and low levels of gonadotropic hormones (LH and FSH). The ligand for GPR54 is encoded by the KISS1 gene, which produces a 54-amino-acid peptide (metastin or kisspeptin-54) that can be cleaved into shorter peptides (kisspeptins 14, 13 and 10) with similar potencies. Kisspeptin administration stimulates gonadotropin release in several species by inducing GnRH secretion from hypothalamic GnRH neurons expressing GPR54. Kisspeptins are produced by neurons located in the AVPV and ARC regions of the hypothalamus. Expression of Kiss1 in these neurons is differentially regulated by sex steroids providing a mechanism by which testosterone or estrogen can regulate GnRH release. The AVPV region is sexually dimorphic with highest expression of kisspeptin in females. Positive feedback by estrogen on expression of Kiss1 in the AVPV region may be responsible for the pre-ovulatory LH surge during the estrus cycle. Central administration of kisspeptin to immature female rats can induce precocious activation of the gonadotropic axis, causing advanced vaginal opening, elevated uterus weight, increased serum levels of LH and estrogen and induce ovulation. Kisspeptins/GPR54 have also been implicated in regulating the estrus cycle of seasonal breeders and in the control of lactational amenorrhea. Expression of Gpr54 and Kiss1 have also been reported in several peripheral tissues including the pituitary, ovary, testes and the placenta raising the possibility that these genes may have additional functions in these tissues. Regulation of kisspeptin expression by peripheral factors such as leptin may be involved in coordinating metabolic status with the reproductive axis.

The kisspeptin (KiSS-1)/GPR54 system in cancer biology

Kisspeptin (KiSS-1) gene, initially described as a melanoma metastasis suppressor gene, encodes a number of peptides (kp-54, kp-14, kp-13, kp-10), which are endogenous ligands to a G protein-coupled receptor, referred as hOT7T175 or AXOR12 or GPR54. So far intensive investigation has provided substantiate evidence supporting the role of KiSS-1/GPR54 system in cancer biology as well as in the regulation of the reproductive function and trophoblast invasion. The precise mechanism by which KiSS-1/GPR54 system is affecting cancer cell growth and metastasis includes complex endocrine, paracrine and autocrine actions. Nevertheless, the detail mechanism of such actions is still under intensive investigation. Herein we review the evidence which support the role of KiSS-1/GPR54 system in cancer biology.

SnoRNA U50 is a candidate tumor-suppressor gene at 6q14.3 with a mutation associated with clinically significant prostate cancer

Deletion of chromosome 6q14-q22 is common in multiple human cancers including prostate cancer, and chromosome 6 transferred into cancer cells induces senescence and reduces cell growth, tumorigenicity and metastasis, indicating the existence of one or more tumor-suppressor genes in 6q. To identify the 6q tumor-suppressor gene, we first narrowed the common region of deletion to a 2.5 Mb interval at 6q14-15. Of the 11 genes located in this minimal deletion region and expressed in normal prostates, only snoRNA U50 was mutated, demonstrated transcriptional downregulation and inhibited colony formation in prostate cancer cells. The mutation, a homozygous 2 bp (TT) deletion, was found in two of 30 prostate cancer cell lines/xenografts and nine of 89 localized prostate cancers (eleven of 119 or 9% cancers). Two of 89 (2%) patients with prostate cancer also showed the same mutation in their germline DNA, but none of 104 cancer-free control men did. The homozygous deletion abolished U50 function in a colony formation assay. Analysis of 1371 prostate cancer cases and 1371 matched control men from a case-control study nested in a prospective cohort showed that, although a germline heterozygous genotype of the deletion was detected in both patients and controls at similar frequencies, the homozygosity of the deletion was significantly associated with clinically significant prostate cancer (odds ratio 2.9; 95% confidence interval 1.17-7.21). These findings establish snoRNA U50 as a reasonable candidate for the 6q tumor-suppressor gene in prostate cancer and likely in other types of cancers.

New technologies used in the study of human melanoma

The amount of information on tumor biology has expanded enormously, essentially due to the completion of the human genome sequencing and to the application of new technologies that represent an exciting breakthrough in molecular analysis. Often these data spring from experimental procedures, such as a serial analysis of gene expression (SAGE) and DNA microarrays, which cannot be defined as hypothesis-driven: it may appear to be a "brute force" approach through which no information can be directly generated concerning the specific functions of selected genes in a definite context. However, interesting results are fruitfully generated, and thus it is important to consider the enormous potential these new technologies possess and to learn how to apply this novel form of knowledge in the emerging field of molecular medicine. This review, after a limited outline regarding several classic aspects of human cutaneous melanoma biology, genetics, and clinical approaches, will focus on the proficient use of up-to-date technologies in the study of the neoplastic disease and on their capability to provide effective support to conventional approaches in melanoma diagnosis, prognosis, and treatment.

Characterization of frequently deleted 6q locus in prostate cancer

The long arm of chromosome 6 is frequently deleted in diverse human neoplasms. Our previous study showed a minimum deletion region between markers D6S1056 and D6S300 on chromosome 6q in primary prostate cancer (CaP). In this study, we further refined a 200-kb minimal region of deletion (6qTSG1) centered around D6S1013 marker. The 6qTSG1 transcripts contained complex multiple splicing variants with low or absent expression in CaP cells. None of the transcripts identified contained open reading frames that code for a protein in the NCBI database. The expression of 6qTSG transcripts revealed interesting hormonal regulation relevant to CaP biology. Expression of 6q TSG transcript was induced in LNCaP cells that were cultured in charcoal-stripped serum medium suggesting an upregulation of 6qTSG transcript by androgen ablation and cell growth inhibition/apoptosis. Induction of 6qTSG1 expression in response to androgen ablation was abrogated in androgen-independent derivatives of LNCaP cells. In summary, we have defined a candidate CaP suppressor locus on chromosome 6q16.1, and deletions of this locus are frequently associated with prostate tumorigenesis. In the light of emerging role of noncoding RNAs in cancer biology including CaP, future investigations of 6qTSG11 locus is warranted.

Transcriptional regulation of KiSS-1 gene expression in metastatic melanoma by specificity protein-1 and its coactivator DRIP-130

Loss of the metastasis suppressor gene, KiSS-1 has been strongly correlated to the progression of metastases in numerous types of cancers. The mechanism through which KiSS-1 is lost during metastasis, however, is still not completely known. Previous studies have shown that genetic material on human chromosome 6q16.3-q23 is essential for KiSS-1 expression in normal tissues. Additionally, microcell-mediated transfer of this chromosome in cancerous tissue results in rescued expression of KiSS-1 and reduced metastatic phenotype. Here, we show that loss of Sp1-coactivator protein DRIP-130, which is encoded by human chromosome 6q16.3-q23, results in reduced KiSS-1 promoter activation in highly malignant melanoma cells. Co-expression of Sp1 and DRIP-130 not only rescues KiSS-1 expression, but also induces an inhibition of the invasive and migratory behavior in highly metastatic melanoma cells, similar to the overexpression of KiSS-1 metastasis suppressor gene in those cells. Furthermore, we demonstrate that KiSS-1 expression is regulated by Sp1 elements within the first 100-bp region of the KiSS-1 promoter and that targeted deletion of a single GC-rich region spanning -93 to -58 interrupts Sp1- and DRIP-130-modulated transcriptional control of KiSS-1 expression. Our results thus suggest that DRIP-130 is a key regulator in KiSS-1 transactivation in normal tissue, and that the loss of DRIP-130 expression, as a result of the gross loss of human chromosome 6q16.3-q23, provokes increased tumor metastasis.

Epigenetic regulation of the tumor suppressor gene TCF21 on 6q23-q24 in lung and head and neck cancer

The identification of tumor suppressor genes has classically depended on their localization within recurrent regions of loss of heterozygosity. According to Knudson's two-hit hypothesis, the remaining allele is lost, either genetically or, more recently identified, through epigenetic events. To date, retrospective analyses have determined promoter methylation as a common alternative alteration in cancer cells to silence cancer-related genes. Here we report an application of restriction landmark genomic scanning that allows for DNA methylation profiling along a region of recurrent loss of heterozygosity at chromosome 6q23-q24. This approach resulted in the identification of a tumor suppressor gene, TCF21, which is frequently lost in human malignancies. We demonstrate that TCF21 is expressed in normal lung airway epithelial cells and aberrantly methylated and silenced in the majority of head and neck squamous cell carcinomas and non-small-cell lung cancers analyzed. TCF21 is known to regulate mesenchymal cell transition into epithelial cells, a property that has been shown to be deficient in carcinomas. We further demonstrate that exogenous expression of TCF21 in cells that have silenced the endogenous TCF21 locus resulted in a reduction of tumor properties in vitro and in vivo.

KiSS1 suppresses metastasis in human ovarian cancer via inhibition of protein kinase C alpha

Metastasis is a vital target for cancer treatment, since the majority of cancer patients die from metastatic, rather than the primary disease. KiSS1 has been identified as a metastasis suppressor gene in melanoma and breast carcinomas. We show here that KiSS1 is also a metastasis suppressor in human ovarian cancer. Overexpression of KiSS1 in ovarian cancer cells inhibits cell migration induced by serum or lysophosphatidic acid (LPA), and colonization in soft agar, but not cell proliferation, representing the characteristics of a metastasis suppressor gene. Furthermore, using an experimental metastatic mouse model, we show that expression of KiSS1 in SKOV3 ovarian cancer cells suppresses >50% metastatic colonization in mice (P < 0.0001). We find that activating protein kinase C (PKC) reverses about 80% of the inhibited cell migration induced by KiSS1, while down-regulation of PKCalpha with shRNA restores KiSS1 effect, providing evidence that inhibiting PKCalpha may be an important mechanism of the effect of KiSS1. These results suggest that KiSS1 is a metastasis suppressor of ovarian cancer and may be a potential molecular target for the treatment.

The KISS1 metastasis suppressor: mechanistic insights and clinical utility

Melanoma is a highly metastatic cancer that accounts for the majority of skin cancer deaths. Unfortunately, very few improvements have been made during the last 20 years in the management of melanoma metastases, which is the major cause of melanoma deaths. Therefore, identification of molecular targets that can be exploited in the clinic to treat metastatic disease is desperately needed. The KISS1 metastasis suppressor gene has emerged as a promising molecular target for the management of metastatic disease. This review compiles data regarding the molecular and biochemical properties of KISS1 and its cognate receptor, focusing on the properties believed to be most pertinent to the use of KISS1 in the clinical setting. In addition, clinical data that supports KISS1 as having a dual role as a prognostic indicator and a therapeutic target for the management of metastatic disease will be highlighted.

Loss of heterozygosity at 6q is frequent and concurrent with 3p loss in sporadic and familial capillary hemangioblastomas

Capillary hemangioblastoma is a benign tumor, occurring sporadically or as a manifestation of von Hippel-Lindau (VHL) disease. Inactivation of the VHL gene at 3p25-26 has been demonstrated in all VHL-associated hemangioblastomas. However, the VHL gene has been found to be inactivated in only 20% to 50% of sporadic tumors. So far, no other gene has been reported to be involved in the development of hemangioblastomas. DNA losses at 6q are frequent alterations in hemangioblastomas, as shown by comparative genomic hybridization. We therefore analyzed 15 hemangioblastomas for loss of heterozygosity (LOH) on chromosome 3p and 6q to reveal the frequency of allelic losses and to determine minimal deleted areas. We detected LOH at 6q for one or more markers in 11 (73%) out of 15 cases (in 9 of 11 sporadic and in 2 of 4 VHL-associated tumors). The analyses revealed a minimal 3-megabase (Mb) deleted region at 6q23-24, where 9 of 11 (82%) informative cases showed LOH. LOH at 3p was seen in 14 out of 15 tumors. LOH occurred concurrently at 6q and 3p in 67% of cases. Our data strongly suggests that a tumor suppressor gene located at 6q23-24 is involved in tumorigenesis of hemangioblastomas, in addition to the VHL gene.

Allelic loss of chromosome 6q in gastric carcinoma

Loss of the long arm of chromosome 6 (6q) has frequently been reported in gastric carcinoma, and most gastric cancer patients have evidence of intestinal metaplasia in the stomach. However, the relationship between loss of chromosome 6q and intestinal metaplasia has not been studied. In the first part of the study, we define the critical deletion region of chromosome 6q using loss of heterozygosity technique (LOH). Seventeen microsatellite markers were used to detect loss of heterozygosity (LOH) in 37 microdissected gastric tumors. We also examined intestinal metaplasia (IM) foci of the stomach in the same cancer patient (17 cases). Losses on chromosome 6q were detected in high frequency (51%) by LOH. Two distinct regions of common allelic loss were identified: one centered on the marker D6S300 (at 6q16.1) and the second on D6S446 (at 6q27), with LOH frequency of 36% and 31.3%, respectively. The deletions fall into 2 discrete regions, suggesting the existence of at least 2 tumor suppressor genes in 6q. The losses at 6q27 were confirmed by fluorescence in situ hybridization study (FISH). In the cases with LOH in the tumor, no LOH were detected in the autologous IM areas, but losses were detected by FISH. In some cases, these genetic changes may be acquired in the transition from normal gastric mucosa to intestinal metaplasia.

KISS1 metastasis suppression and emergent pathways

Metastatic disease is the most critical impediment to cancer patient survival. However, comparatively little is known concerning the intricate pathways which govern the complex phenotypes associated with metastasis. The KISS1 metastasis suppressor gene inhibits metastasis in both in vivo melanoma and breast carcinoma models. Despite its clear physiological activity, the mechanism of KISS1 remains unclear. Recent identification of a 54 amino acid peptide of KISS1, termed metastin or kisspeptin-54, and its cognate G-protein coupled receptor (hOT7T175, AXOR12, GPR54) have provided additional clues and avenues of research. While studies have attributed KISS1 with modulation of NFkappaB regulation, experiments with metastin and its receptor implicate MAP kinase pathways and also suggest the potential of autocrine, paracrine and endocrine roles. Impacts on motility, chemotaxis, adhesion and invasion have each been documented in disparate cell lines and conflicting observations require resolution. Nevertheless, mounting clinical evidence, particularly the loss of KISS1 in metastases, correlates KISS1 and metastin receptor expression with human tumor progression. Together, the data substantiate roles for these molecules in metastasis regulation.

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.

Polymorphic mutations of the Mn-SOD gene in intact human lymphocytes and oral squamous cell carcinoma cell lines

Mutations of the superoxide dismutase (SOD) genes are associated with neoplastic and non-neoplastic diseases. However, the existence of polymorphic mutations of manganese SOD (Mn-SOD) has not been explored in squamous cell carcinoma (SCC) cells or in normal cells. In the present study, we examined mutations in the 5' flanking region of the Mn-SOD gene and Mn-SOD mRNA using 10 human oral SCC (OSC) cell lines and intact lymphocytes obtained from 10 healthy donors and one patient with OSC. The polymerase chain reaction products of DNA obtained from lymphocytes revealed insertions at many sites (-1833, -1575, -1093, -1056, -325, -318, and -310) in 10 of the 11 donors. Transitions and (or) transversions were also observed at -1638 and -216 in lymphocytes from six donors and one donor, respectively. In DNA obtained from OSC cells, insertions and transitions and (or) transversions were more frequent than those in DNA from lymphocytes. In addition, deletions at -1341 and -1288 were observed in all lines except for one line. In these mutations, the transcription factor binding sites were not involved except for the AP-2 binding site (-102) in three cell lines. In Mn-SOD mRNA, Val at -9 position was varied to Ala in lymphocytes from two donors and three OSC cell lines, respectively. In the remaining cell lines, Mn-SOD mRNA from lymphocytes and OSC cell lines revealed heterozygosity (Ala/Val) and homozygosity (Val/Nal), respectively. The Mn-SOD activities in lymphocytes were 3.8-5.8 x 10(-4) U/10(6) cells and the activities in OSC cell lines were 1.8-8.3 x 10(-4) U/10(6) cells. These Mn-SOD activities were not correlated with the mutations of DNA and mRNA. From these results, it is indicated that polymorphic mutations of Mn-SOD exist in human normal cells and that the deletions might be obtained in the course of malignant transformation of OSC although decrease in Mn-SOD activity is not involved in the transformation.

Genotypic analysis of primary and metastatic cutaneous melanoma

Microdissection genotyping was performed on 16 cases of melanoma, including two cutaneous and one lymph node metastases. Three benign nevi were used as controls. Where possible, tumor was microdissected at several sites. Genotyping involved assessment of loss of heterozygosity [LOH]), which was accomplished using a panel of nine polymorphic tetranucleotide microsatellites. Polymerase chain reaction was performed on the normal tissue sample to establish microsatellite heterozygous status. Informative markers were then tested on microdissected lesional tissue and scored for the presence and extent of allelic imbalance (AI). Microsatellite informativeness varied from 33% to 66%. Benign nevi were without AI. All invasive melanomas manifested acquired allelic loss, which involved 75% or 100% of the markers shown to be informative for each subject. Eleven of 13 (84%) primary melanomas demonstrated intratumoral heterogeneity of AI consistent with development of tumor subclones with differing genotypic profiles within thin as well as thick melanomas. Although a consistent pattern did not emerge among the markers, LOH of 9p21 (D9S254) occurred in 60% (9/15) of the cases followed by 40% of cases displaying LOH of 1p34, p53, 10q (MXI1), and 10q23 (D10S520) and 25% with 5q21 (D5S 592) abnormalities. A third of the cases including the metastatic foci demonstrated two different patterns of AI affecting alternative alleles of the same genomic marker within different parts of the melanoma. Two melanomas in situ did not display LOH of any markers in the informative cases although the in situ component in the invasive tumors had allelic losses that were in part similar to the invasive areas. The results of this study support the expanded use of microdissection genotyping and explore other markers to define the unique mutational profile for malignant melanoma that may complement other histologic characteristics of melanoma.

Cloning and characterization of the common fragile site FRA6F harboring a replicative senescence gene and frequently deleted in human tumors

The common fragile site FRA6F, located at 6q21, is an extended region of about 1200 kb, with two hot spots of breakage each spanning about 200 kb. Transcription mapping of the FRA6F region identified 19 known genes, 10 within the FRA6F interval and nine in a proximal or distal position. The nucleotide sequence of FRA6F is rich in repetitive elements (LINE1 and LINE2, Alu, MIR, MER and endogenous retroviral sequences) as well as in matrix attachment regions (MARs), and shows several DNA segments with increased helix flexibility. We found that tight clusters of stem-loop structures were localized exclusively in the two regions with greater frequency of breakage. Chromosomal instability at FRA6F probably depends on a complex interaction of different factors, involving regions of greater DNA flexibility and MARs. We propose an additional mechanism of fragility at FRA6F, based on stem-loop structures which may cause delay or arrest in DNA replication. A senescence gene likely maps within FRA6F, as suggested by detection of deletion and translocation breakpoints involving this fragile site in immortal human-mouse cell hybrids and in SV40-immortalized human fibroblasts containing a human chromosome 6 deleted at q21. Deletion breakpoints within FRA6F are common in several types of human leukemias and solid tumors, suggesting the presence of a tumor suppressor gene in the region. Moreover, a gene associated to hereditary schizophrenia maps within FRA6F. Therefore, FRA6F may represent a landmark for the identification and cloning of genes involved in senescence, leukemia, cancer and schizophrenia.

Chromosomal aberrations related to metastasis of human solid tumors

The central role of sequential accumulation of genetic alterations during the development of cancer has been firmly established since the pioneering cytogenetic studies successfully defined recurrent chromosome changes in specific types of tumor. In the course of carcinogenesis, cells experience several genetic alterations that are associated with the transition from a preneoplastic lesion to an invasive tumor and finally to the metastatic state. Tumor progression is characterized by stepwise accumulation of genetic alterations. So does the dominant metastatic clone. Modern molecular genetic analyses have clarified that genomic changes accumulate during the development and progression of cancers. In comparison with the corresponding primary tumor, additional events of chromosomal aberrations (including gains or allelic losses) are frequently found in metastases, and the incidence of combined chromosomal alterations in the primary tumor, plus the occurrence of additional aberrations in the distant metastases, correlated significantly with decreased postmetastatic survival. The deletions at 3p, 4p, 6q, 8p, 10q, 11p, 11q, 12p, 13q, 16q, 17p, 18q, 21q, and 22q, as well as the over-representations at 1q, 8q, 9q, 14q and 15q, have been found to associate preferentially with the metastatic phenotype of human cancers. Among of them, the deletions on chromosomes 8p, 17p, 11p and 13p seem to be more significant, and more detail fine regions of them, including 8p11, 8p21-12, 8p22, 8p23, 17p13.3, 11p15.5, and 13q12-13 have been suggested harboring metastasis-suppressor genes. During the past decade, several human chromosomes have been functionally tested through the use of microcell-mediated chromosome transfer (MMCT), and metastasis-suppressor activities have been reported on chromosomes 1, 6, 7, 8, 10, 11, 12, 16, and 17. However, it is not actually known at what stage of the metastatic cascade these alterations have occurred. There is still controversial with the association between the chromosomal aberrations and the metastatic phenotype of cancer. As the progression of human genome project and the establishment of more and more new techniques, it is hopeful to make clear the genetic mechanisms involved in the tumor metastasis in a not very long future, and provide new clues to predicting and controlling the metastasis.

Targeting multiple genetic aberrations in isolated tumor cells by spectral fluorescence in situ hybridization

PURPOSE

Tumorigenesis is characterized by the stepwise accumulation of multiple genetic changes that modify specific growth controls and cell survival. Conventional fluorescence in situ hybridization (FISH) assays reliably target one to three probes in a single hybridization. Simultaneous detection of more than three chromosomal or gene targets should increase the overall power of molecular cytogenetics by permitting detection of multiple genetic aberrations at the single cell level.

METHOD

Spectral FISH (S-FISH) is an innovative molecular cytogenetic approach that can target many specific chromosomal aberrations in interphase and metaphase cells in a single hybridization, using combinatorial fluorescence and digital imaging microscopy.

RESULTS

S-FISH is a reliable means to identify disease-specific aberrations at the DNA level in individual tumor cells in hematopoietic disorders and malignant melanoma.

CONCLUSION

S-FISH is a sensitive assay for the diagnosis and monitoring of disease-specific or patient-specific genetic aberrations, with significant clinical application in oncology for early detection of new or re-emerging abnormal clones, allowing for earlier therapeutic intervention.

Defining the region(s) of deletion at 6q16-q22 in human prostate cancer

Deletion of the long arm of chromosome 6 (6q) frequently occurs in many neoplasms, including carcinomas of the prostate and breast and melanoma, suggesting the location of a tumor-suppressor gene or genes at 6q. At present, however, the region of deletion has not been well defined, and the target gene of deletion remains to be identified. In this study, we analyzed 44 primary prostate cancers with 16 polymorphic markers for loss of heterozygosity (LOH) by using PCR-based techniques. We also examined 23 cell lines/xenografts of prostate cancer with 38 markers for LOH by the method of homozygosity mapping of deletion. LOH at 6q16 - q22 was detected in 21 of 44 (48%) primary tumors and in 12 of 23 (52%) cell lines/xenografts. Two regions of LOH were defined. One was 7.5 cM at 6q16 - q21 between markers D6S1716 and D6S1580, and the other was 4.3 cM at 6q22 between D6S261 and D6S1702. Whereas no correlation was found between LOH at 6q16-q22 and patient age at diagnosis or Gleason score, tumors at higher stage appear to have more frequent LOH. These findings suggest that deletion of 6q16 - q22 is a frequent event in prostate cancer, and that the deletion originates from two distinct regions. These results should be useful in identifying the target gene(s) of deletion at 6q.

Cytogenetic characterization of complex karyotypes in seven established melanoma cell lines by multiplex fluorescence in situ hybridization and DAPI banding

We report the use of multiplex fluorescence in situ hybridization (M-FISH) to resolve chromosomal aberrations in seven established melanoma cell lines with hypotriploid to hypertetraploid complex karyotypes. By simultaneous identification of all human chromosomes in single FISH experiments using a set of 52 directly labeled, whole chromosome painting probes, cryptic chromosomal translocations and the origin of unclear chromosomal material in structural rearranged and marker chromosomes could be identified, refining the tumor karyotypes in all seven cell lines. The number of structural aberrations in each cell line assigned with combined M-FISH and DAPI banding analysis ranged from 15 to 45. Altogether, 275 breakpoints could be assigned to defined chromosomal regions or bands. The chromosome arms 1p, 6q, 7p, 9p, and 11q which are known to be nonrandomly associated with melanoma tumorigenesis, were frequently involved in chromosomal breaks and/or copy number changes. This study also demonstrated the practical usefulness of combining M-FISH with conventional cytogenetic banding techniques for the characterization of complex tumor karyotypes with massive genomic alterations.

Heterogeneity of allelic deletions within melanoma metastases

During the initiation and progression of malignant melanoma, a series of different genetic events accumulate on several different chromosomes. The biological heterogeneity of tumour cells presents a major problem, preventing effective treatment of melanoma. To examine the degree of genetic heterogeneity, we searched for allelic losses (loss of heterozygosity; LOH) on chromosomes 9p, 9q, 1p and 17p, examining different areas within human melanoma metastases. All of the examined metastases were informative within at least one dissected area for at least one marker. Out of 29 areas in 11 melanoma metastases, 58% showed LOH with at least one marker. On chromosome 9p21-22, eight out of 26 informative loci (31%) showed LOH at D9S171 (three not informative), two out of 18 (11%) at IFNA (11 not informative) and seven out of 24 (29%) at D9S169 (five not informative). LOH on chromosome 9q22.3 was examined by the microsatellite marker D9S12; three out of 24 areas (12.5%) showed LOH, and five were not informative. Deletions on chromosome 1p were assessed using D1S450. Four out of 25 (16%) showed LOH; four were not informative. Deletions on chromosome 17p13 were examined with TP53; two out of 21 cases (9%) showed LOH, and eight were not informative. Our data demonstrate an impressive heterogeneity of allelic losses in the investigated chromosomal areas within the same metastatic lesion. This suggests that there is not one specific genetic alteration that accounts for melanoma progression to metastases. Rather there seem to be multiple genetic alterations accumulating even on the same chromosome, and progression from melanoma to metastases is paralleled by the accumulation of clones harbouring multiple genetic abnormalities.

Putative tumor suppressor loci at 6q22 and 6q23-q24 are involved in the malignant progression of sporadic endocrine pancreatic tumors

Our previous comparative genomic hybridization study on sporadic endocrine pancreatic tumors (EPTs) revealed frequent losses on chromosomes 11q, 3p, and 6q. The aim of this study was to evaluate the importance of 6q losses in the oncogenesis of sporadic EPTs and to narrow down the smallest regions of allelic deletion. A multimodal approach combining polymerase chain reaction-based allelotyping, double-target fluorescence in situ hybridization, and comparative genomic hybridization was used in a collection of 109 sporadic EPTs from 93 patients. Nine polymorphic microsatellite markers (6q13 to 6q25-q27) were investigated, demonstrating a loss of heterozygosity (LOH) in 62.2% of the patients. A LOH was significantly more common in tumors >2 cm in diameter than below this threshold as well as in malignant than in benign tumors. We were able to narrow down the smallest regions of allelic deletion at 6q22.1 (D6S262) and 6q23-q24 (D6S310-UTRN) with LOH-frequencies of 50.0% and 41.2 to 56.3%, respectively. Several promising tumor suppressor candidates are located in these regions. Additional fluorescence in situ hybridization analysis on 46 EPTs using three locus-specific probes (6q21, 6q22, and 6q27) as well as a centromere 6-specific probe revealed complete loss of chromosome 6 especially in metastatic disease. We conclude that the two hot spots found on 6q may harbor putative tumor suppressor genes involved not only in the oncogenesis but maybe also in the malignant and metastatic progression of sporadic EPTs.