Expression Of Polo-like Kinase 1 (PLK1) In Different Pathological Casificated Lung Cancer

BackgroundPrimary bronchial cancer (lung cancer) is one of the most frequent male malignant disease, a serious threat to human health and life, which accounts for 16% of total malignant neoplasm and 28% of mortality from malignant neoplasm. Although surgery is the most reliable treatment so far, an investigation has indicated that 70% of patients with lung cancer have already lost the surgery opportunity when they received medical examinations. Therefore, it is one of the most critical problems and projects to identify early diagnoses, create effective treatments, and improve prognoses for lung cancer. Among them, the genes that affect tumor proliferation are more noticeable.In recent years, some research showed that the polo family exhibits a comprehensive regulation in cellular mitoses. Many studies demonstrated ahigh expression of PLKl in most human tumors and suggested prognoses in some patients with high expression level of PLKl. If the expression of PLKl is inhibited with different methods, the proliferation of tumor cells will change accordingly. This indicates that PLKl might be a novel marker of tumors and become a new target of tumor gene therapy.To understand the relation of PLKl and lung cancer, this experiment applies fluorescent real-time quantitative PCR (FQ-PCR) to detect the PLKl mRNA expression of specimens of lung cancer and benign diseases and analyze the PLKl gene expression of different pathological tissues of lung cancer and cell lines. With the correlation analyses of PLKl expression and pathological types, the function and degree of PLKl in gene diagnoses and treatments are further evaluated.Objects and MethodsThere were 97 samples of branchofiberoscopic specimens collected at Sir Run Run Shaw Hospital from March 2003 to April 2004. There were 69 samples of lung cancer, including 34 samples of squamous lung cancer , 17 samples of adenocarcinoma, 18 samples of cellule lung cancer. The culture cell strains are NCI-H446, a human small cell lung cancer strain and A549, a human lung adenocarcinoma strain. These two strains were grown in RPMI-1640 culture solution containing 10% calf serum. The culture is at 37°C, with 5% CO2 concentration and saturated moisture. Thecells were digested to extract RNA at the logarithmic growth phase. RNA of tissue samples and cells was extracted and transcribed into cDNA that was used for PCR. The Ct value was calculated by FQ-PCR. The PLK1 mRNA expressions of lung cancer and benign disease, SCLC and NSCLC tissues, SCLC and NSCLC cell lines were compared. The DNA bands were observed in 2% agarose electrophoresis. The data were shown in mean ± standard error (X±S). The two groups were analyzed by independent sample t test with SPSS 12.0 for windows.ResultsThe experiment showed that the PLK1 mRNA expression of lung cancer specimens (0.124±0.194) is significantly higher than that of benign disease specimens (0.037±0.042), p=0.03. However, there is no obvious statistical difference by the comparison of PLK1 mRNA expression between SCLC and NSCLC tissues (p=0.08). The box plot of fluorescent quantity suggested that there is a suggestive but inconclusive evidence of higher expression level in cellule than non-cellule lung cancer.The cell count method was applied to calculate cell proliferation time of two lung cancer cell lines at the logarithmic growth phase. The results showed that the time of NCI-H446, a SCLC cell line is shorter than that of A549, adenocarcinoma cell line. The mean of NCI-H446 PLK1 mRNA expression is 0.238±0.053 and the mean of A549 is 0.129±0.046. There is astatistical difference between the PLKl mRNA expression of two cell lines (t =-3.830, p =0.03).ConclusionsThe PLKl mRNA expression of lung cancer specimens is significantly higher than that of lung benign disease specimens, which indicates that PLKl might be a potential tumor marker of lung cancer.There is no significant difference of PLKl mRNA expression between SCLC and NSCLC, but the fluorescent quantity box plot showed suggestive but inconclusive evidence of higher level in SCLC than NSLC. The PLKl mRNA expression of NCI-H446, a line of the shorter proliferation time is higher than that of A549, a line of the longer proliferation time, which indicates that the expression of PLKl might be related to the cell proliferation activity.