Expression And Significance Of Pin1 And Cyclin D1 In Acute Leukemia

IntroductionA common feature of tumorigenesis is abnormal regulation of cell cycle, which leads to an uncontrolled proliferation of cells. Acute leukemia is a clonal malignancy disease of hematopoietic cells characterized by the excessive proliferation and abnormal differentiation. The deregulation of many oncogenes, tumor suppressorgenes and their related genes produce abnormal proteins and lead to disruption of cell cycle, cells proliferation excessively and as a result, leukemogenesis is initiated. Phosphorylation and dephosphorylation as well as specific protein degradation are important factors for the accurate control of progression of cell cycle.Phosphorylation regulation is a common living phenomenon in cell. Many proteins participate the cell function through their phosphorylation or dephosphorylation. Phosphorylation-dependent prolyl isomerization is a critical regulatory mechanism in phosphorylation process. The recent researches indicate that there are two configurations of the pSer/Thr-Pro motifs in proteins, that is Cis and Trans. The transformation from cis to trans in pSer/Thr-Pro motifs after binding by Pin1 regulates the proteins function. Pin1 regulates the activity of mitotic protein such as cdc25,NIMA by binding with them, which modulate cell cycles. The overexpression of Pin1 is involved in the tumor development and progression. Cyclin D1 is a checkpoint of G1/S transition. Inhibition of cyclin D1 causes cells arrest in G1 phase, which suppresses tumor cells growth. The studys demonstrate that cyclin D1 is overexpressed in many tumors.To explore the expression of Pin1 and its relationships with cyclin D1 in Acute Leukemia, the expressions of Pin1 and cyclin D1 in bone marrow mononuclear cells from untreated Acute Leukemia patients, AL-CR patients and control group were detected by immunocytochemical staining (S-P three-step method). Their function in the leukemogenesis was further discussed.Materials and method1. Patients: (1) De novo leukemia group: Samples from 62 cases of de novo acute leukemia were collected. Patients were 10-75 years (mean 35 years old) with 42 males and 20 females. The whole patients were divided into two groups:â‘ Acute Myelogenous Leukemia (n=40), including M₀ 2 cases, M₁ 2 cases, M₂ 20 cases, M₃ 7 cases, M₄ 3 cases, M₅ 3 cases, M₆ 2 cases,M7 1 case;â‘¡Acute lymphocytic Leukemia (n=22); The acute leukemias were diagnosed by French-American-British classification. (2) AL-CR group: bone marrow samples from patients (n=35) who reached CR after chemotherapy. It was further divided into AML-CR and ALL-CR.â‘¢The control group: Bone marrow samples from non-malignant hematologic diseases (n=15). All the samples were obtained from the patients treated in the Hemotologic Department of the First Affiliated Hospital of Zhengzhou University through May to December of 2006.2. Sample processing: bone marrow mononuclear cells were separated from 1ml bone marrow of untreated Acute Leukemia patients and control patients. The BMNC were load on slides and detected by immunocytochemical staining(S-P three-step method) for the expressions of Pin1, and cyclin D1.3. Statistical analysis: The data were analyzed with Fisher's exact test and Spearman correlation by SPSS11.0 and the standard of statistic significance was established asα=0.05.Results1. The expression of Pin1 in control group was dim or negative. The positive rate of Pin1 in initialed novo AL was 59.7% as positively or strong positively expressed in nuclear or cytoplasm with 65% in AML, 50 % in ALL. There was no significance between the positive rate of AML and ALL (P>0.05). The positive rate of Pin1 in AL-CR was 2.9% and 4.2% in AML-CR, but negative in ALL-CR. There was no significance between the positive rate of AML-CR and ALL-CR (P>0.05). The expression of Pin1 in de novo AL was significantly higher than that in AL-CR and control (P<0.05). And the expression of Pin1 in AML and ALL was significantly higher than that in AML-CR and ALL-CR, respectively (P<0.05).2. The expression of cyclin D1 in control group was weak or negative. The positive rate of cyclin D1 in initialed novo AL was 56.5% as positively or strong positively expressed in nuclear or cytoplasm with 50% in AML, 68 % in ALL. There was no significant difference between the positive rate in AML and in ALL (P>0.05). The positive rate of cyclin D1 in AL-CR was 2.9% and 9.1% in ALL-CR, but negative in AML-CR. There was no significant difference between the positive rate in AML-CR and in ALL-CR (P>0.05). The expression of cyclin D1 in de novo AL was significantly higher than that in AL-CR and control (P<0.05). The expression of cyclin D1 in AML and ALL was higher than that in AML-CR and ALL-CR, respectively (P<0.05).3. There was a positive correlation between Pin1 and cyclin D1 (r=0.465, P <0.05).4. There was no significant correlation between the level of Pin1, cyclin D1 and patient's age, sex, WBC, and infiltration of diseases (P>0.05).Conclusion1. Both Pin1 and cyclin D1 expressions were significantly higher in AML and ALL than that in control and AL-CR, which suggested that Pin1,cyclin D1 participate in leukemogenesis through promoting malignant proliferation of leukemia cells.2. Furthermore, this study also showed that Pin1 level correlated with cyclin D1 positively, which suggests that up-regulation of Pin1 enhances the expression of cyclin D1, acting as an upsteam factor of cyclin D1.