| IntroductionWith the rapid growth of incidence of lung cancer, more and more studies have been made about its occurrence, development and metastatic mechanism in recent years. Most researchers have reported that uncontrollable cell proliferation is just one of the causes of tumor, apoptotic abnormality is another important factor to be attributed to. Thus it is suggested that apoptosis - related genes play an important even key role in the development of cancers.Fas is an important apoptosis - inducing gene. It was discovered and named respectively by Trauth and Yonehara in 1989. Fas is also designated as Apo - 1 or CD95 , and its protein product is a kind of transmembrane protein ( membrane Fas, mFas) , which belongs to the nerve growth factor ( NGF) and tumor necrosis factor(TNF) receptor superfamily. It can transfer apoptosis signals to cytoplasm by means of binding with Fas ligand( FasL) or anti -Fas antibody. It has been proved that Fas receptor has two forms: membrane Fas (mFas) and soluble Fas (sFas). The sFas was first reported by Cheng et al in 1994 and it is believed that sFas can inhibit the binding of mFas and FasL by competing against FasL. Consequently, it prevents the apoptosis of cell. Fas is mainly distributed in cell membrane. If there is alternative splicing in the course of transcribing and translating, it will lead to the lacks of transmembrane domain and creat sFas. At present, at least three kinds of isoforms have been identified and among them the most common one is the derivation from alternative splicing of lacking a length of 63bp of transmembrane domain. sFas is mainly distributed in serum and its key role is to prevent apoptosis induced by FasL - mFas through bindingwith FasL. Therefore, the serum sFas levels can reflect the changes of apoptosis indirectly.It is not clear where sFas is derived from. Three possibilities have been suggested about it. First, sFas may be derived from tumor cells or the cells which are closely linked to the tumor cells;Second, sFas may be derived from lymphocytes or tumor infiltrating lymphocytes;Third, sFas may be derived from unidentified cells which are highly activated by tumor cell. sFas is formed because of lacks of transmembrane domain which is caused by mRNA alternative splicing. The increase in the expressions of sFas mRNA indicates the increase in the transcribing activation of sFas mRNA, and the increase in the transcribing activation of sFas mRNA is one of the possible routes from which sFas is derived. Serum sFas levels of 70 patients with primary lung cancer and sFas mRNA expressions of 14 lung cancer tissues are studied in the experiment. The discussion centers on the changes of serum sFas level in patients with lung cancer and the expressions of sFas mRNA in the patients' lung cancer tissues. Furthermore , with the discussion on the expressions, the paper tries to find out whether or not the lung cancer cell is one of the sources of serum sFas. It is hoped that the discussion, as well as the experiment would provide a new marker for the ba-sical and clinical application of lung cancer.Subject and MethodSubjects:There are 70 lung cancer patients, of which 32 are squamous cell carcinomas,20 are of adenocarcinomas, and 18 of are small cell carcinomas. Among these 70 patients, 3 are of I a stage,9 are of I b stage, 4 are of II a stage, 8 are of H b stage, 10 are of Ma stage, 16 are of Mb stage,20 are of Wstage. The 20 controls are of the same age and sex as the 70 patients.Methods:1. The serum sFas levels in 70 patients with primary lung cancer and 20 controls are measured by Sandwich enzyme immunoassay ( ELISA).2. The sFas mRNA expressions in 14 samples of resected lung cancer tissueand 6 samples of para - cancer normal lung tissue are tested by reverse transcription - polymerase chain reaction ( RT - PCR).Result1. The serum sFas level in patients with lung cancer is significantly higher in comparison with controls ( P < 0. 01 ) , and the result is statistically significant.2. The serum sFas level is significantly higher in groups of different pathologic type in comparison with controls ( P <0. 01) , and the result is statistically significant. There is no significant difference in the serum sFas levels among different pathologic type groups ( P >0. 05).3. The serum sFas levels of patients with lung cancer, from stage I to stage IV, is significantly higher than that of the controls ( P <0. 01) , and the result is statistically significant. The serum sFas level of patients in stage IV is significantly higher than that of the patients at the other three stages (P <0. 01) , and the result is statistically significant. There is no significant difference among groups from stage I to stage HI ( P > 0. 05 ).4. As far as pathologic type is concerned, the expressions of sFas mRNA in lung cancer tissues are significantly higher compared with controls (P <0. 01) , and the result is statistically significant. There is no significant difference among these lung cancer tissues (P >0. 05).Conclusion1. The serum sFas level in patients with primary lung cancer is significantly higher compared with healthy persons.2. The serum sFas level in patient with primary lung cancer is not related to the pathologic type. However, the serum sFas in patients of stage IV is much higher than that in patients of other stages. Based on this finding, it can be concluded that the significant increase in sFas is more likely to be associated with metastasis.3. The sFas mRNA expressions in lung cancer tissues is significantly higher than it is in normal lung tissues. Based on this finding, it can be concluded that lung cancer cell may be one of the routes from which sFas is derived.Key word... |
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