Análise do gene CDKN1B/p27kip1 em pacientes com neoplasia endócrina múltipla tipo 2 / CDKN1B/p27kip1 gene analysis in patients with multiple endolcrine neopasia type 2 (MEN2)

INTRODUÇÃO: Na Neoplasia Endócrina Múltipla tipo 2 (NEM2), o desenvolvimento do Carcinoma Medular de Tireoide (CMT), Feocromocitoma (FEO) e Hiperparatireoidismo primário (HPT) está associado à mutações germinativas ativadoras no proto-oncogene RET. Casos de CMT esporádico podem apresentar mutações somáticas no RET (~40%). A variabilidade fenotípica observada em casos de CMT e FEO familiais associados à NEM2 indica o envolvimento de eventos genéticos adicionais que seriam responsáveis pelas diferenças clínicas observadas nos indivíduos afetados (idade de desenvolvimento, progressão e agressividade do tumor). Outras alterações genéticas no RET como duplas mutações, SNPs e haplótipos específicos podem influenciar na susceptibilidade, agressividade e modulação do fenótipo NEM2. Entretanto, os estudos de outros genes envolvidos no processo da tumorigênese NEM2 ainda estão em andamento. Recentemente foi mostrado que RET ativado controla a expressão de proteínas inibidoras do ciclo celular (p18 e p27). Mutações germinativas no gene p27 foram recentemente associadas à susceptibilidade de tumores neuroendócrinos e estão associadas à síndrome NEM4 (Neoplasia endócrina múltipla tipo 4). Mutações somáticas, inativadoras de p27, são raramente encontradas em vários tipos de tumores. Entretanto, diversos estudos documentaram que a redução na expressão e a sublocalização citoplamática de p27 são controladas por alterações pós-transducionais e/ou epigenéticas. OBJETIVOS: o estudo teve como objetivos avaliar a participação de genes, recentemente associados ao RET ativado, em tumores de pacientes com NEM2 e também verificar se polimorfismos no gene p27 estariam atuando como moduladores de fenótipo em uma grande família com NEM2. CASUÍTICA: foram analisadas 66 amostras tumorais advindas de 36 pacientes com diagnóstico clínico e genético de NEM2 e 28 indivíduos pertencentes a uma grande família com NEM2A-CMTF e mutação C620R no gene RET. MÉTODOS:...

INTRODUCTION: In Multiple Endocrine Neoplasia type 2 (MEN2) the development of medullary thyroid carcinoma (MTC), pheochromocytoma (PHEO) and primary hyperparathyroidism (HPT) are associated with activating germline mutations in RET proto-oncogene. Cases of sporadic MTC may have somatic RET mutations (~ 40%). The phenotypic variability observed in cases with familial MTC/MEN2 and PHEO/MEN2 indicates the probable involvement of additional genetic events that could be responsible for the clinical differences observed in the affected individuals (age development, progression and aggressiveness of the tumor). Other genetic alterations such as RET double mutations, SNPs and specific haplotypes may influence susceptibility, aggressiveness and MEN2 phenotype modulation. However, studies of other genes involved in the tumorigenesis of MEN2 are still in progress. Recently, it was shown that the activated RET controls the expression of cell cycle inhibitory proteins (p18 and p27). Germline mutations in the p27 gene have recently been associated with the susceptibility to neuroendocrine tumors and are associated with the MEN4 syndrome (Multiple endocrine neoplasia type 4). Somatic inactivating mutations p27 are rarely found in many types of tumors. However, several studies have documented that reduced expression and subcellular location of p27 is controlled by post-transductional changes and/or epigenetic factors. OBJECTIVES: This study aimed to evaluate the role of genes recently associated with RET activated in tumors from MEN2 patients and also check whether polymorphisms in the p27 gene would be acting as modulators of phenotype in a large MEN2 family. PATIENTS: We analyzed 66 tumor samples from 36 patients with clinical and genetic diagnosis of MEN2 and from 28 individuals belonging to a large family with FMTC/MEN2A and RET C620R mutation. METHODS: The analyses of somatic p27, p15, p18 and RET...

Expression and significance of CDK4,p18,p19 in canceration of esophageal epithelium / 肿瘤研究与临床

Objective To investigate the role of cell cycle regulatory protein CDK4,p18,p19 in the genesis and development of esophageal squamous cell carcinoma (SCC).Methods Tissue microarray and immunohistochemical method (Envision) were used to detect the protein expression of CDK4,p18,p19 in 120 cases of esophageal tissues.The results were statistically analyzed.Results The positive rate of CDK4 protein expression in normal esophageal epithelium was low [28.3 % (34/120)],it increased in esophageal intraepithelial neoplasia [32.5 % (39/120)],and it was high in esophageal SCC [84.2 % (101/120)],which increased with the degree of SCC differentiation decreasing gradually.There was significant differences between the SCC and normal esophageal epithelium or esophageal intraepithelial neoplasia (x2= 76.004,P ＜0.05; x 2= 65.897,P ＜ 0.05).The expression of CDK4 in group with lymphatic metastasis [93.88 % (46/49)]was higher than without it [71.43 % (55/71)] (x2= 5.860,P ＜ 0.05).The positive rates of p18,p19 protein expression in normal esophageal epithelium were high [34.2 % (41/120),29.2 % (35/120)],it decreased in esophageal intraepithelial neoplasia [19.2 % (23/120),15.0 % (1 8/120)] (x 2= 134.481,P ＜ 0.05; x 2 = 141.376,P ＜ 0.05),but it were high in esophageal SCC [63.3 % (76/120) and 61.7 % (74/120)] which decreased with the degree of SCC differentiation gradually increased.There were significant differences between the normal esophageal epithelium and esophageal intraepithelial neoplasia,esophegeal intraepithelial neoplasia and SCC,normal esophageal epithelium and SCC (p 18:x 2 = 6.903,48.296,20.429,P ＜ 0.05; p1 9:x2 = 6.998,55.276,25.565,P＜ 0.05).CDK4 protein expression was correlated with both p18 and p19 (r =0.696,0.630,P ＜0.05),and there was significant positive correlation between the protein expression of p18 and p19 (r =0.833,P ＜0.05).Conclusion Cell cycle regulatory gene CDK4,p18,p19 get involved in the genesis and development of esophageal squamous cell carcinoma.Their protein expressions are closely related to canceration of esophageal epithelium.

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.

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.

Alterations of p16INK4A and p18INK4C, Human Papillomavirus infections and Expression of the Cell Cycle Associated Proteins in Cervical Carcinomas / 대한산부인과학회잡지

OBJECTIVE: We analyzed the gene status of p16INK4A, p18INK4C, the expression of cell cycle associated proteins (p16INK4A, p18INK4C, cyclin D1, CDK4, pRb, and p53), and human papillomavirus (HPV) infection to investigate whether the inactivation of these genes participated in carcinogenesis, and to evaluated the expression of cell cycle associated proteins and HPV infections. METHODS: We examined forty-one primary cervical carcinomas (17 adenocarcinomas, 13 keratinizing squamous cell carcinomas, and 11 nonkeratinizing squamous cell carcinomas) using PCR, comparative multiplex PCR, PCR-SSCP, methylation-specific PCR, and immunohistochemistry. RESULTS: Ninety percent of cervical carcinomas showed HPV infection. HPV type 16 was detected in 41% and HPV type 18 was found in 44%. Homozygous deletions at p16INK4A gene were observed in 2 cases, but the mutation of p16INK4A and alterations of p18INK4C gene were not detected. The promoter hypermethylation for p16INK4A in nine cases (31%) of 29 cervical carcinomas was found. Expression of p16INK4A protein was observed in 93% and p18INK4C protein expression was noted in 78%. Positive immunostaining for cyclin D1 was only identified in 5%, whereas positive immunostaining for CDK4 was observed in 95%. Expression of pRb protein was found in 93% and p53 protein in 24% of cervical carcinomas. CONCLUSION: These results suggest that high risk HPV infections and methylation of the p16INK4A promoter region seem to play an important role in the pathogenesis of cervical carcinomas. Alterations of p18INK4C gene and cyclin D1-CDK4 pathway does not contribute significantly in the cervical carcinogenesis.