Inhibitory Effect Of Blocking MAPK/ERK Signaling Pathway On Endometrial Cancer Xenografts

Background and ObjectiveEndometrial carcinoma (EC) is one of the most common malignant tumors in the female reproductive system. The morbidity of EC has increased markedly in recent years. The growth of endometrial cells can be promote by the long-term effect of estrogen without the counteraction of progesterone. It can also lead to the malignant transformation of endometrial cells and increase the risk of endometrial cancer. However, the exact mechanism of endometrial cancers is still unclear.Currently, it has been widely recognized that estrogen can increase the cell proliferation through the transcriptional effects of nuclear genes. But, it has been found that the mitogen activated protein kinase (MAPK) signaling pathway in EC cells can be activated by estrogen by Non-gene transcription effect. The abnomal activation of this signaling pathway is closely related to the development of many kinds of malignant tumors such as breast cancer, ovarian cancer, endometrial cancer, hepatoma, colon cancer and so on. Nowadays, some studies had shown that blocking the MAPK signal pathway can inhibit the proliferation of endometrial carcinoma cells. PD98059is a specific inhibitor of MAPK signal pathway; it can inhibit the proliferation of cancer cells and induce cell apoptosis. We have studied the inhibitory effect of PD98059on different endometrial carcinoma cell lines Ishikawa and HEC-1A, which has different estrogen receptor levels, in nude mice, to explore the further value of PD98059in treating endometrial carcinoma.Materials and Methods1MaterialsEndometrial carcinoma cell lines:HEC-1A and Ishikawa is a kind gift from Professor Lihui Wei, Peking University People’s Hospital. BALB/c nude mice, female,4-6weeks, purchased from the Beijing Vital River Laboratory Animal Technology Co.Ltd and rose in the Experimental Animal Center of Henan Province (SPF).2MethodsHuman endometrial carcinoma cells Ishikawa bearing ER and HEC-1A with low ER status were cultured and separately subcutaneously injected into12BALB/c nude mice to establish endometrial cancer xenograft tumor models, then they were divided randomly into2groups (n=6each), respectively, to receive normal saline (NS), PD98059(50mg/kg) for3weeks, twice a week intraperitoneally. Tumor volume was measured, tumor growth curve was drawn and tumor inhibitive rate was calculated. Mice were sacrificed3weeks after administration. HE was staining to test histopathological change of the tumor specimens. TUNEL testing carried on observing the difference of cell apoptosis, and the expressions of P-ERK in different teams were detected by Western blot.3Statistical analysisAll the analyses were treated by SPSS17.0statitic software. Statistical evaluation were performed using Normality test, the homogeneity of variance test and T test,"Alpha equals0.05"(α=0.05) was considered to be statistically significant. Results1.3weeks after administration, compared with the control group[average volume:(3110.60±244.81) mm3], the average xenograft tumor volume of Ishikawa cells treated with PD98059[average volume:(1782.83±122.93) mm3] is much smaller, the difference is significant(t=-4.847, P<0.01). The average xenograft tumor volume of HEC-1A cells treated with PD98059is (1573.21±108.05) mm3, it was (2664.73±114.55) in the control group. The tumor volumes of the experimental group is significantly less than the control group(t=-6.932, P<0.001).2. HE staining confirmed that the formated tumors are endometrial carcinoma. Tumor cells in the groups treated with PD98059were larger, and the salient histopathologic features were present, such as pyknotic (shrunken and dark) and karyorrhexis, while more apoptotic cells or necrotic cells were observed. What’s more, there are inflammatory cells infiltration and significant fibrosis.3. Through TUNEL tests, we found the apoptosis and necrosis of tumor cells significantly increased in the groups treated with PD98059. In the xenografts of Ishikawa, the apoptosis index (AI) of the control group is (3.33±1.18)%and the PD98059group is (18.57±2.69)%, the difference is significant(t=-12.705, P<0.05). In the xenografts of HEC-1A, the AI of the control group is (4.23±0.63)%and the PD98059group is (21.33±3.07)%, There are significant difference between them (t=-13.374,P<0.05).4. Western blot show the expressions of P-ERK in treated groups were lower than that in control group in both Ishikawa and HEC-1A cell xenografts.Conclusions1. PD98059can block the mitogen-activated protein kinase signal pathway, reduce the expressions of P-ERK, promote tumor cells apoptosis and inhibit the tumor growth.So, the signal transduction pathways can be used as a new target for the treatment of endometrial cancer. PD98059is expected to become a new targeted drugs for the treatment of endometrial cancer. 2. PD98059can significantly inhibited the ER-positive Ishikawa cells and HEC-1A cell lines which is ER-negative.This provide a new and effective method for the treatment of ER-negative endometrial cancer.