| More recently, elevated or deregulated expression of c - myc has been detected in a wide range of human cancers, and is often associated with aggressive, poorly differentiated tumours. Concomitant with promoting cell growth and proliferation, c - myc inhibits terminal differentiation of most cell types, and sensitizes cells to apoptosis. The carboxy - terminal basic - helix loop helix zipper (bHLHZ) domain of c - myc binds MAX - also a bHLHZ protein - to form MYC MAX heterodimers that are capable of binding specific DNA sequences , such as the E-box sequence CACGTG.Telomerase is a ribonucleoprotein enzyme that synthesises telomeres after cell division and maintains chromosomal length and stability thus leading to cellular immortalisation. At each cell division, cells lacking the telomerase lose te-lomeric repeat DNA; they enter senescence after telomeres become critically short. Human telomerase reverse transcriptase ( hTERT) gene is the rate - limiting determinant of telomerase reactivation. As telomere maintenance seems to be essential for tumorigenesis, the recent identification of hTERT as a direct gene target of c - myc, represents an important mechanism for c - myc - induced immortalization.Ameloblastoma (AB) is the most frequently occurring odontogenic tumor, the frequency of which is 63.2%. The benign tumor may progressively invade the jaw, recur locally and transform malignantly, therefore, treated as a semi -malignancy tumor. The present study aims to measure the expression of c - myc and hTERT mRNA in AB and to explore the relationship between c - myc and hTERT expressions to investigate the molecular mechanisms in the regulation of telomerase; and examine the association between c - myc and the clinicopatho-logical characteristics of the tumor specimens in AB to provide some theoretic basis for the diagnosis, therapy and prognosis of AB.Materials and methodsThe specimens were surgically removed from 54 patients with AB ( primary AB 31 cases, recmrent AB 19 cases, malignant AB 4 cases) , 16 patients with odontogenic keratocyst (OKC) and 7 patients with normal oral mucosa (NOM) at the First Affiliated Hospital of China Medical University between 1996 -2001. We detected c - myc and hTERT mRNA by in situ hybridization. With regard to in situ expression, the extent of staining was scored: ( - ) fewer than 10% positive or no staining; ( + ) 10% -40% positive; ( + + ) 40% -70% positive; ( + + + ) more than 70% of cell positive. SPSS for 11.0 statistical software was used to solve the data. Chi ?square test was used to analyze the correlation, and fishers exact test was used when the frequency of a cell in a 2 x2 table was <5. Kendall rank correlation was determined between c - myc and hTERT expression. The probability of P < 0.05 was regarded as statistically significant.Resultc - myc mRNA was positive expressed in the plasma of peripheral cells and stellate central cells, negative in the granular cells in AB. It's indicated that the proliferation and differentiation of AB were heterogeneity. The expression of c -myc mRNA was negative or weaker in NOM (14.3% ) , weaker or moderate in OKC (75% ) , moderate or strong in AB (81.5% ) , respectively. There was a significant difference in these three groups (x =15. 488, P < 0. 05). The difference between primary, recurrent and malignant AB was significant ( X = 16.912,P < 0.05). x2 test indicated that there were no correlation between c -myc mRNA expression with age, sex, position and histological type (P >0. 05 ). But c - myc expression is related with cell differentiation and angiogene-sis.hTERT mRNA was positive expressed judging purple granule in plasma. The positive ratio of NOM ,OKC and AB was 14.3% ,87.5% ,94.4% , respectively. There was a significant statistical difference in these three groups ( P <0. 001). hTERT mRNA was stronger as AB recurred or transformed malignantly ( P < 0. 05 ). There was no significant differences between hTERT mRNA and age, sex, position and histological type (P >0.05). A moderate correlation betwee...
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