Experimental Study Of The Relationship Between WNT Signaling Pathway And Basal Cell Carcinoma

Objective: Basal cell carcinoma (BCC) was also known as basal cell epithelioma. The malignancy is derived from the epidermis or cutaneous appendages. It is one of the most commonly occurring cutaneous malignancies. The pathogenesis of these tumors is still unknown. BCC is particularly prevalent in the elder, it has been only demonstrated that Basal cell carcinoma characteristically arises in body areas exposed to the sun and is most common on the head and neck. Exposure to ultraviolet radiation is generally accepted as the major cause of basal-cell carcinoma. Exposures to ionizing radiation, arsenic and the mutation of P53 and PTCH have also been linked to the development of basal cell carcinoma. Therefore, it is suggested that BCC is most resulted from hereditary factors and environmental factors in the development of tumor genesis. Recently, the relation between WNT signaling pathway and tumors is one of the international hotspot. It is suggested that WNT may play an essential role in embryogenesis and carcinogenesis of BCC.WNT signal pathway is a multi-link, multi-functional growth signal pathway, with the complicated regulation and control of exterior and interior cells. WNT signal pathway regulates growth and development accurately. However, the over-activation or imbalance of WNT will cause the body dysplasia or tumor formation. More and more experiments have showed that the members of WNT included Frizzled,β-catenin and TCF/LEF etc. The mutations of these genes may induce the abnormal accumulation ofβ-catenin, thenβ-catenin translocates to the nucleus where it interacts with transcription factors such as TCF/LEF (T cell factor/lymphocyte enhancer factor), and engages the downstream target gene.β-catenin is the positive regulator of WNT, Frizzled is the membrane receptor of WNT and TCF4 plays an important role in engaging the taget gene. The objective of our experiment is to investigate the expression of these components of WNT in BCC, explore the clinical and pathological significance, and discuss the relation of their abnormal expression with the occurrence, progression and prognosis in BCC.Methods: The patients were derived from the department of Pathology and the department of Dermatology in the Fourth Affiliated Hospital of Hebei Medical University from May 2005 to Jun 2008, who were diagnosed as BCC and seborrheic keratosis (SK) clinically and histopathologically. The patients of BCC included 20 males and 12 females, age changed from 46 to 78 years (mean 53.36±7.95), course changed from 1 to 20 years (mean 5.45±1.89). 26 specimens of SK were taken as controls, which included 15 males and 11 females, age changed from 38 to 71 years (mean43.35±6.12). There was no significant difference in sex and age between the patients and controls. And the 15 healthy specimens were taken from the skin of surgical traumatic patients.In this study, H&E staining was performed in the histopathology. The expression pattern of WNT1,β-catenin and TCF4 was investigated by immunohistochemical SP method. The results were analyzed by Mann-Whitney U rank sum test and Spearman rank correlation analysis by SPSS 13.0.Results:1 Histopathological examination resultsThe tumor was composed of basaloid cells of different sizes, shapes, ranging from mass or cords, the cytoplasm was fewer and nuclei was larger, round or long spindle. At the periphery of the masses of cells, the columnar cells may be characteristically arranged like fence palisading. There were many lymphocyte infiltrations around the tumor stroma.2 Immunohistochemical results2.1 The expression of WNT1: The expression of WNT1 was stained in the membrane. In the lesions of BCC, the positive cells were mainly distributed in poorly differentiated cancer nest, of which 20 cases were strong positive, 5 cases were positive, 3 cases were weak positive and 4 cases were negative. In 26 cases of the SK lesions, the positive cells were mainly concentrated in the prickle cell layer, of which 2 cases of strong positive, 8 cases of positive, 7 cases of weak positive and 9 cases of negative. In normal skin, WNT1 was stained mainly in appendages. epidermal basal layer and the prickle cell layer were negative expression. The expression of WNT1 was stronger in BCC than in SK. There was a significant difference between BCC and SK.2.2 The expression ofβ-catenin: In normal epithelial cells,β-catenin was staining in the membrane, without cytoplasm and (or) nuclear staining. In SK and BCC lesions, it is showed that the expression ofβ-catenin in cell membrane is weak or loss. There was varying degrees of cytoplasmic and /or nuclear staining (ie, ectopic expression). In 32 cases of BCC, 28 cases existed ectopic expression ofβ-catenin, ectopic expression ratio was 87.50% (28/32). In 26 cases of SK, there was ectopic expression ofβ-catenin in 12 cases; ectopic expression ratio was 46.15% (12/26). It is revealed that there was a significant difference by statistical analysis.2.3 The expression of TCF4: The expression of TCF4 was stained in nucleus. A few number of tumor cells was stained in cytoplasmic. In BCC cases,19 cases were strong positive, 8 cases were positive, 3 cases were weak positive and 2 cases were negative. The full-thickness tissues were negative expression in SK and normal skin. statistical analysis showed that there was a significant difference between BCC and SK.2.4 Correlative analysis on the expression of WNT1,β-catenin and TCF4 in BCC: The expression of WNT1,β-catenin and TCF4 was analyzed with Spearman rank correlation test. The results have showed that: in BCC skin lesions, WNT1 andβ-catenin,β-catenin and TCF4, WNT1 and TCF4 were all positively correlated.Conclusions:1 The expression of WNT1 in the lesions of BCC was significantly stronger than that in SK. It is suggested that the strong expression of WNT1 may play an important role in genesis and development of the basal cell carcinoma.2 The ectopic expression ratio ofβ-catenin in the lesions of BCC were significantly higher than that in SK. It is suggested that the ectopic expression ofβ-catenin may activate downstream target genes, change the cell cycle, interfer with normal cell proliferation, differentiation and induce the occurrence of BCC.3 The expression of TCF4 in the lesions of BCC was significantly stronger than that in SK. It is presumed that the abnormal signal may activate the downstream gene. It is suggested that TCF4 may play an important role in genesis and development of BCC.4 Correlative analysis on the expression of WNT1,β-catenin and TCF4 in BCC: The results of correlative analysis have showed that the strong expression of WNT1 may activate the WNT signaling pathway, which led toβ-catenin translocating into the nucleus, then formβ-catenin/TCF4 complexes and activate downstream target genes. The inter-synergy of the three genes was involved in the tumor cell proliferation, differentiation, invasion and metastasis, etc.