| Objective: CD44 is a highly glycosylated transmembrane protein encoded by a unique 20-exon gene on chromosome 11 in humans. It displays many variant isoforms (CD44v) generated by alternative splicing of exons 2v to lOv. In addition to hyaluronic acid, CD44 interacts with a large number of extracellular matrix components including fibronectin, laminin, collagen, serglycin, osteopontin, chondroitin and heparan sulphate as well as cellular ligands including L-selectin and CD44 itself. Many of these ligand interactions are modulated by variant exons. CD44 modulates a variety of cellular functions including adhesion, proliferation, presentation of growth factors, apoptosis, cell migration and metastatic behavior. While the standard form of CD44 is expressed on virtually all haematopoietic cells, expression of variant isoforms is highly restricted and correlated with specific processes, such as leukocyte activation and malignant transformation. In the rat, expression of CD44v is linked to the lymphatic spread of tumor cells, and expression of CD44v suffices to initiate tumor progression. CD44 variants has been associated with poor prognosis and increased metastatic spread in a number of haematological and non-haematological malignancies. In addition, CD44v expression in peripheral blood leukocytes of non-Hodkin's lymphoma correlated with response to therapy and, inversely, with tumor progression. CD44v6 have been implicated in the metastaticpotential of rat carcinoma cell lines. The expression of human's CD44v6 is very low on normal haematopoietic cells and high on malignant hematopoietic cells in non-Hodgldn's lymphoma and myeloma, which is involved in their progression. Expression of increased levels of exons v6 is associated with poor prognosis in acute leukaemia and can stimulates the AL cells proliferation, suggesting a role of CD44v6 in the development of the acute leukemia.p27kip1 (p27) is a member of the universal cyclin dependent kinase inhibitor (CDKI) family. It is an important regulator of G1 progression and negatively regulates cell proliferation. p27kip1 is expressed highly in GO, where it binds tightly and inhibits cyclin E/CDK2. p27kip1 expression is regulated by cell contact inhibition and by specific growth factors, such as transforming growth factor (TGF-β). In addition to its role as a CDKI, p27kip1 has several other functions such as a putative tumor suppressor gene, regulator of drug resistance in solid tumors, promoter of apoptosis, and a role in cell differentiation. There are considerable evidences indicating that the inactivation of p27kip1 is a fundamental step for the development of malignancies. Although p27kip1 is rarely mutated in human cancers, the level of p27kip1 protein expression decreases during the progression of tumors in some epithelial, lymphoid, and endocrine tissues. This decrease occurs mainly at the post-translational level with protein degradation by the ubiquitin-proteasome pathway. A large number of studies have characterized p27kip1 as an independent prognostic factor in various human cancers, including breast, colon, and prostate carcinomas, and low p27kip1 expression is significantly associated with a poor prognosis. Several investigations indicated the expression of p27kip1 in acute leukemia had a positive relation with prognosis of acute leukemia and the cases with high p27kip1 expression had a significantly increased disease-free survival.In order to investigate the relationship among CD44v6, p27kip1 and acute leukemia, and to observe their clinical significance, the study examined the expression of CD44v6 and p27ldpl protein in bone marrow cells from 50 cases of acute leukemia and 10 cases of normal control by flow cytometry and SP immunocytochemistry technique, respectively.Materials and method: ①Subjects were divided into three groups: The de novo acute lymphocytic leukemia (ALL) group (n=15, Male 10, Female 5, Mean age 27.3y); The de novo acute myelogenous leukemia(ANLL) group (n=35, Male 21, Female 14, Mean age 38.0y), it included M1 3 cases, M2 11 cases, M37 cases, M4 5 cases, Ms 9 cases according to the diagnostic standard worked out by FAB in 1985. The evaluation of curative effects consult The criterition for diagnosis and curative effects of hematologic disease edited by zhinan zhang; The control (NL) group (n=10, Male 4, Female 6, Mean age 39.3y). ②The mononuclear cells of bone marrow of all subjects were collected and tested the positive percentage of p27kip1 protein expression by immunocytochemical method(Count 500 cells)and the positive percentage of CD44v6 protein expression by flow cytometry(Count 1,0000 cells). ②The results were analyzed with analysis of variance, chi-square test, Wilcoxon signed rank test and Fisher' s exact test of probabilities using SPSS10.0 statistical software. The standard of statistic significance was set up when a=0.05.Results: ①The positive cell percentage of CD44v6 expression in ALL, ANLL and NL decreased gradually. The results are (27.11 ±21.50)% in the de novo ALL group, (23.95±19.68)% in the de novo ANLL group, and (6.52±6.29)% in the control group. The positive rate of CD44v6 in ANLL and ALL are significantly higher than that in control group (P<0.05). ②The positive cell percentage of p27kip1 protein expression in ALL, ANLL, and NL decreased gradually. The results are (50.37± 28.70)% in the de novo ALL group, (36.00±22.00) % in the de novo ANLL group and (18.42±10.64) % in the control group. The positive rate of p21kip1 in ALL and ANLL are significantly higher than that in control group (P<0.05), as well as between ALL and ANLL (P<0.05). ③The complete remission rate in the group of CD44v6>24.90% is significant lower than that in the group of CD44v6≤ 24.90% (P<0.05), ④The complete remission rate in the group of p27kip1 >40.31% is significant higher than that in the group of p27kip1≤40.31% (p<0.05). ⑤The expression of CD44v6 and p27kip1 have no apparent relationship with sex, age, white blood cell number and FAB subtypes. ⑥There was a negative correlation between the expression of CD44v6 andthe expression of p27kip1 in AL (r =- 0.478, P<0.05). ⑦The complete remission rate in the low CD44v6 and high p27kip1 group is higher than the low CD44v6 and high p27kip1 group, but there is no difference among three groups (P>0.05). The complete remission rate in the high CD44v6 and low p27kip1 group is lower than the high CD44v6 or the low p27kip1 group, but there is no difference among three groups (P>0.05).Conclusion: ①The positive percentage of CD44v6 was increased in ALL and ANLL leu kemia cell. It suggested that CD44v6 may play a role in the development of the acute leukemia. ②There is significant difference of the complete remission rate in the group of CD44v6>24.90% than in the group of CD44v6< 24.90%. It suggests that CD44v6 may be an independent prognosis index. ③The positive percentage of p27kip1 protein expression increased in AL and had mislocalisation to the cytoplasm. It suggested that the p27kip1 protein may play a complex role in the development of the acute leukemia. ④There is significant difference of the complete remission rate in the group of p27kip1>40.31% than that in the group of p27kip1 ≤40.31%. It suggests that p27kip1 protein is in relation to the effect of initial chemical therapy. So that the lower p27kip1 expression may associated with poor prognosis in acute leukemia and is an independent prognostic marker. ⑤The positive percentage of CD44v6 and p27kip1 had a negative correlation in AL. The simultaneous assays of CD44v6 and p27kip1 expression in AL have a better predictive value in prognosis than checking respectively.
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