Hypermethylation Analysis of p16INK4a and p15INK4b Promoters in Chronic Lymphocytic Leukaemia Patients and Normal Individuals

@#Introduction: Chronic Lymphocytic Leukaemia (CLL) is a common type of leukaemia in persons of predominantly European descent but is rare in the Asian population. Disparities in CLL incidence among people of Asian and European descent may be related to the genetic make-up of the two different populations. Hypermethylation event might be one of the silencing mechanisms that inactivate the tumour suppressor genes in CLL. The aim of this study was to determine the hypermethylation status of p16INK4a and p15INK4b among CLL patients and normal individuals. Materials & Methods: A total of 25 CLL patients and 25 normal individuals were recruited for this study and their genomic DNA were extracted from the peripheral blood. The hypermethylation status of p16INK4a and p15INK4b were determined using Methylation Specific-PCR (MS-PCR) whereas DNA sequencing method was applied to selected samples for validation of the MS-PCR results. We also evaluated the association between hypermethylation of these genes with the clinical and demographic characteristics of each group of subjects. Results: Among the CLL patients, p15INK4b partialmethylation occurred in 6 (24%) subjects while methylation occurred in 1 (4%) subject. All the remaining patients were unmethylated at p15INK4b. All the samples showed unmethylation at p16INK4a. Statistically significant associations were found between p15INK4b hypermethylation with the presence of CLL (p=0.01) and with race (p=0.02). Conclusion: Further study using a larger sample size is warranted to explore the significance of DNA methylation incidence among the CLL patients of the Malaysian population. Hence, we suggest that hypermethylation at p15INK4b has a huge influence that kick-starts CLL disease among Malaysians and MS-PCR technique is applicable to be used in methylation study.

p15(Ink4b) Loss of Expression by Promoter Hypermethylation Adds to Leukemogenesis and Confers a Poor Prognosis in Acute Promyelocytic Leukemia Patients / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: The p15(Ink4b) gene exerts its influence as an inhibitor of cyclin-dependent kinases and is frequently associated with hematological malignancies. Inactivation of this gene through DNA methylation has been found to be the most prevalent epigenetic alteration reported, with a high frequency in all French-American-British subtypes of acute myeloid leukemias, including acute promyelocytic leukemia (APL). In this study,we investigated the prognostic significance of p15 gene promoter hypermethylation and its expression in APL patients of Kashmir (North India). MATERIALS AND METHODS: p15 gene promoter hypermethylation was conducted by methylation-specific polymerase chain reaction, while its subsequent expression analysis was carried out by semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: Of the 37 patients, 16 (43.2%) were found to have methylated p15 genes. Of these 16 cases, seven (43.8%) were methylated partially and nine (56.2%) were found to have complete methylation. Moreover, nine of the 37 patients (24.3%) who presented with leukocytosis at their baseline had complete p15 gene methylation as well (p < 0.05). Semiquantitative RT-PCR showed a complete loss of p15 expression in nine patients with complete methylation coupled with leukocytosis (p=0.031), while seven patients with partial methylation showed decreased p15 expression. Six patients relapsed during the maintenance phase of treatment and were found to have a completely methylated p15 gene and no p15 mRNA. CONCLUSION: Complete methylation and loss of p15 gene expression causes susceptibility to relapse and decreased survival in APL patients. Thus, p15 promoter hypermethylation is a prospective prognostic indicator and a reliable clinical aid in assessment of patients with APL.

p15(Ink4b) Loss of Expression by Promoter Hypermethylation Adds to Leukemogenesis and Confers a Poor Prognosis in Acute Promyelocytic Leukemia Patients / Journal of the Korean Cancer Association, 대한암학회지

PURPOSE: The p15(Ink4b) gene exerts its influence as an inhibitor of cyclin-dependent kinases and is frequently associated with hematological malignancies. Inactivation of this gene through DNA methylation has been found to be the most prevalent epigenetic alteration reported, with a high frequency in all French-American-British subtypes of acute myeloid leukemias, including acute promyelocytic leukemia (APL). In this study,we investigated the prognostic significance of p15 gene promoter hypermethylation and its expression in APL patients of Kashmir (North India). MATERIALS AND METHODS: p15 gene promoter hypermethylation was conducted by methylation-specific polymerase chain reaction, while its subsequent expression analysis was carried out by semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: Of the 37 patients, 16 (43.2%) were found to have methylated p15 genes. Of these 16 cases, seven (43.8%) were methylated partially and nine (56.2%) were found to have complete methylation. Moreover, nine of the 37 patients (24.3%) who presented with leukocytosis at their baseline had complete p15 gene methylation as well (p < 0.05). Semiquantitative RT-PCR showed a complete loss of p15 expression in nine patients with complete methylation coupled with leukocytosis (p=0.031), while seven patients with partial methylation showed decreased p15 expression. Six patients relapsed during the maintenance phase of treatment and were found to have a completely methylated p15 gene and no p15 mRNA. CONCLUSION: Complete methylation and loss of p15 gene expression causes susceptibility to relapse and decreased survival in APL patients. Thus, p15 promoter hypermethylation is a prospective prognostic indicator and a reliable clinical aid in assessment of patients with APL.

Expressions of antisense non-coding RNA in INK4 locus and tumor suppressors in peripheral blood lymphocytes of patient with cirrhosis and hepatocellular carcinoma / 中国中西医结合急救杂志

Objective To investigate the clinical diagnostic and differential diagnostic values of antisense non-coding RNA in the INK4 locus (ANRIL) and tumor suppressors (p14ARF, p15INK4b and p16INK4a) mRNA expression levels in peripheral blood lymphocytes of patients with cirrhosis and hepatocellular carcinoma. Methods The patients with hepatocellular carcinoma and cirrhosis admitted in Shantou Central Hospital from October 2013 to April 2014 were selected. The real-time quantitative reverse transcription-polymerase chain reaction (RT-qPCR) was used to detect ANRIL, p14ARF, p15INK4b and p16INK4a mRNA expression levels of peripheral blood lymphocytes. The subjects having taken physical health examinations in outpatient clinics were assigned in the healthy control group. Results During the study period, 19 cases of hepatocellular carcinoma, 24 cases of cirrhosis, and 31 healthy controls were finally enrolled. In the hepatocellular carcinoma group, the mRNA expression level of ANRIL was significantly higher than that of the healthy control group (?Ct:13.07±0.62 vs. 12.45±0.84, P0.05). There were also no statistically significant differences in p14ARF and p16INK4a mRNA expressions among the three groups (all P>0.05). Conclusion The elevation of ANRIL and descent of p15INK4b mRNA expression levels in peripheral blood lymphocytes in patients with liver lesion can be used as the reference indicators for the early diagnosis of hepatocellular carcinoma and to predict their prognoses.

A combination of STI571 and BCR-ABL1 siRNA with overexpressed p15INK4B induced enhanced proliferation inhibition and apoptosis in chronic myeloid leukemia

p15INK4B, a cyclin-dependent kinase inhibitor, has been recognized as a tumor suppressor. Loss of or methylation of the p15INK4B gene in chronic myeloid leukemia (CML) cells enhances myeloid progenitor formation from common myeloid progenitors. Therefore, we examined the effects of overexpressed p15INK4B on proliferation and apoptosis of CML cells. Overexpression of p15INK4B inhibited the growth of K562 cells by downregulation of cyclin-dependent kinase 4 (CDK4) and cyclin D1 expression. Overexpression of p15INK4B also induced apoptosis of K562 cells by upregulating Bax expression and downregulating Bcl-2 expression. Overexpression of p15INK4B together with STI571 (imatinib) or BCR-ABL1 small interfering RNA (siRNA) also enhanced growth inhibition and apoptosis induction of K562 cells. The enhanced effect was also mediated by reduction of cyclin D1 and CDK4 and regulation of Bax and Bcl-2. In conclusion, our study may provide new insights into the role of p15INK4B in CML and a potential therapeutic target for overcoming tyrosine kinase inhibitor resistance in CML.

Mutational analysis of genes p14ARF, p15INK4b, p16INK4a, and PTEN in human nervous system tumors

The cancer is one of the most common and severe problems in clinical medicine, and nervous system tumors represent about 2% of the types of cancer. The central role of the nervous system in the maintenance of vital activities and the functional consequences of the loss of neurons can explain how severe brain cancers are. The cell cycle is a highly complex process, with a wide number of regulatory proteins involved, and such proteins can suffer alterations that transform normal cells into malignant ones. The INK4 family members (CDK inhibitors) are the cell cycle regulators that block the progression of the cycle through the R point, causing an arrest in G1 stage. The p14ARF (alternative reading frame) gene is a tumor suppressor that inhibits p53 degradation during the progression of the cell cycle. The PTEN gene is related to the induction of growth suppression through cell cycle arrest, to apoptosis and to the inhibition of cell adhesion and migration. The purpose of the present study was to assess the mutational state of the genes p14ARF, p15INK4b, p16INK4a, and PTEN in 64 human nervous system tumor samples. Homozygous deletions were found in exon 2 of the p15INK4b gene and exon 3 of the p16INK4a gene in two schwannomas. Three samples showed a guanine deletion (63 codon) which led to a loss of heterozygosity in the p15 gene, and no alterations could be seen in the PTEN gene. Although the group of patients was heterogeneous, our results are in accordance with other different studies that indicate that homozygous deletion and loss of heterozygosity in the INK4 family members are frequently observed in nervous system tumors.

INK4 Family -A promising target for 'gene-regulating chemoprevention' and 'molecular-targeting prevention' of cancer

Inactivation of the p16(INK4a) gene is one of the most frequent defects that contribute to oncogenesis in human cancer, since it is a tumor-suppressor gene. Therefore, functional restoration of p16(INK4a) is one of the most effective methods for cancer prevention. We proposed the concept of 'gene-regulating chemoprevention' and 'molecular-targeting prevention' of cancer, which assumes that transcriptional regulation by drugs on tumor-suppressor genes or functionally similar genes to the tumor-suppressor genes contributes to the prevention of human malignancies. The p16(INK4a) homologs p15(INK4b), p18(INK4c) and p19(INK4d) have been recently identified, and these four members constitute the INK4 family of proteins. All directly bind to cyclin D-cyclin dependent kinase (CDK) 4/6 and are therefore specific inhibitors of these complexes. We recently showed that histone deacetylase (HDAC) inhibitors, promising chemopreventive and chemotherapeutical agents, induce p15(INK4b) and p19(INK4d) gene expression and cause growth arrest, suggesting that both genes are important molecular targets for HDAC inhibitors. Furthermore, we found that 12-O-tetradecanoylphorbol-13-acetate (TPA), which is widely used as a tumor promoter and protein kinase C activator, promotes human cancer cell growth through the down-regulation of p18(INK4c) gene expression. This suggests that a mouse two-stage carcinogenesis model using TPA might partially represent the most common human carcinogenesis pathway related to RB. Our results suggest that the INK4 family consists of attractive and promising molecular targets for the 'gene-regulating chemoprevention' and 'molecular-targeting prevention' of cancer.

INK4 Family\\---A Promising Target for \lqGene-Regulating Chemoprevention\rq and \lqMolecular-Targeting Prevention\rq of Cancer---

Inactivation of the p16INK4a gene is one of the most frequent defects that contribute to oncogenesis in human cancer, since it is a tumor-suppressor gene. Therefore, functional restoration of p16INK4a is one of the most effective methods for cancer prevention. We proposed the concept of ‘gene-regulating chemoprevention’ and ‘molecular-targeting prevention’ of cancer, which assumes that transcriptional regulation by drugs on tumor-suppressor genes or functionally similar genes to the tumor-suppressor genes contributes to the prevention of human malignancies. The p16INK4a homologs p15INK4b, p18INK4c and p19INK4d have been recently identified, and these four members constitute the INK4 family of proteins. All directly bind to cyclin D-cyclin dependent kinase (CDK) 4/6 and are therefore specific inhibitors of these complexes. We recently showed that histone deacetylase (HDAC) inhibitors, promising chemopreventive and chemotherapeutical agents, induce p15INK4b and p19INK4d gene expression and cause growth arrest, suggesting that both genes are important molecular targets for HDAC inhibitors. Furthermore, we found that 12-O-tetradecanoylphorbol-13-acetate (TPA), which is widely used as a tumor promoter and protein kinase C activator, promotes human cancer cell growth through the down-regulation of p18INK4c gene expression. This suggests that a mouse two-stage carcinogenesis model using TPA might partially represent the most common human carcinogenesis pathway related to RB. Our results suggest that the INK4 family consists of attractive and promising molecular targets for the ‘gene-regulating chemoprevention’ and ‘molecular-targeting prevention’ of cancer.

Homozygous Deletion of p16INK4 and p15INK4B Genes in Human Advanced Ovarian Carcinoma / 대한산부인과학회잡지

OBJECTIVE: p16INK4 and p15INK4B genes are known to be tumor suppressor genes which reside in p21 region of chromosome 9 and are related to cell cycle control as an inhibitor of cyclin-dependent-kinase. We designed this study to search for deletion and decreased expression of p16INK4 and p15INK4B genes in advanced ovarian carcinomas. METHODS: Polymerase chain reaction (PCR)-based analysis was performed to search for deletion of p16INK4 and p15INK4B using DNA extracted from frozen tissue in liquid nitrogen of thirty-one advanced ovarian carcinoma patients. The intensities of PCR bands were analyzed using an imaging densitometer to determine gene dosage in tumor samples and the relative gene dosage was calculated by comparing band intesity of p16INK4 or p15INK4B with that of beta-globin gene. Homozygous deletions were assigned to tumors in which the ratio was reduced to less than 25% in any one of exons of p16INK4 and p15INK4B. Immunohistochemical techniques were used to study the expression of p16INK4. p16-negative cells were characterized by the absence of nuclear staining, whereas cytoplasmic staining was variable. Clinico-pathologic features, complete remission rates and survivals were analyzed according to the status of p16INK4 and p15INK4B genes. RESULTS: Homozygous deletion of p16INK4 was detected in 12.9% of advanced ovarian carcinoma patients and that of p15INK4B in 35.5%. Clinico-pathologic features such as FIGO stage, histological grade, serum CA-125 levels were not different from groups with homozygously deleted p16INK4 and p15INK4B to those with normal genes. The survival of patients (13 [6-20] months) with homozygously deleted p16INK4 was significantly shorter than that (30 [8-52] months) of patients with normal p16INK4 (p=0.046; Log-rank test). CONCLUSION: These observations indicate that deletions of p16INK4 and p15INK4B gene might be involved in tumorigenesis of ovarian carcinoma and could be useful as a prognostic factor. A prospective, controlled study with more patients will be mandatory in the future.

Methylation of p15INK4B gene and its mechanism in patients with myelodysplastic syndrome and leukemia / 中国病理生理杂志

AIM: To explore the relationship between hypermethylation of p15INK4B gene and the pathogenesis of hematopoietic malignances. METHODS: The expression and methylation of p15INK4B gene and the expression of DNA methyltransferase genes (DNMTs) in bone marrow cells from 54 cases with hematopoietic malignances were detected by RT-PCR, Western blot, and methylation-specific PCR. RESULTS: The p15INK4B gene was methylated more often in high-risk myelodysplastic syndrome (MDS) patients, patients at blast phase of chronic myeloid leukemia (CML-BP) and acute leukemia patients than that in low-risk MDS patients (P