Study On The Relationship Of ERK And Its Inhibitor With Adenoid Cystic Carcinoma Of Salivary Gland

As one of the most common malignant tumor of salivary gland, adenoid cystic carcinoma (ACC) takes up 27% of all salivary gland carcinomas, 1% of head and neck carcinomas. With high invasive potential, it tends to invade blood vessels and nerves , prone to recurrence and distant metastasis at early stage of tumor growth. How to prevent and treat the recurrence and metastasis of adenoid cystic carcinoma effectively is a focus and challenge of research currently, further research into the molecular regulation mechanism of invasion and metastasis of adenoid cystic carcinoma, the determinationof main target, blocking of the key process, may provide research basis for new method of tumor prevention and treatment.The development of tumor involves a number of cellular events and physiological process, disorder of cellular signaling pathway plays an important role. Ras/Raf/MEK/ERK pathway (ERK pathway) is a typical cascade tranducting extracellular signal into cell nucleus and thereafter stimulating transcription level increase. Researches showed that ERK is over-expressed or abnormally activated in many malignant tumor tissues or cell lines such as hepatocellular carcinoma, breast cancer, squamous carcinoma of head and neck, prostate cancer and kidney cancer, indicating that abnormal regulation of ERK pathway is closed related to the development and progression of malignant tumors. Currently ERK pathway inhibitor is widely investigated, with PD98059 most popular. PD98059 can adhere to disactivated MEK1 ATP locus to inhibit the effect of Raf, therefore block the phosphysating activation of ERK1/2 by MEK1, PD98059 is an ideal blocking agent for in vitro study on the effect of ERK pathway in cell lines.We investigated the effect of ERK pathway inhibitor PD98059 on cell proliferation of adenoid cystic carcinoma of salivary gland and metastasis by in vitroand in vivo study. 1. In vitro study, we detected the expression of phosphysated ERK1/2 in highly metastatic adenoid cystic carcinoma cell line( ACC-M), positive expression of ERK1/2 was found in the cytoplasm of ACC-M. With ACC- M exposed to various concentration of PD98059(0> 12^ 25^ 5(K lOOumol/L), we found that cell proliferation of ACC- M was inhibited to different levels, compared to the control, the concentration of lOOumol/L significantly inhibit the proliferation of ACC- M (P<0.05), implying that the activation of ERK pathway was associated with tumor cell proliferation of adenoid cystic carcinoma. 2. In vivo study, we established experimental lung metastasis model of adenoid cystic carcinoma of salivary gland by injecting ACC- M cell into the lateral tail vein of nude mice. 6 weeks later, the mice were injected peritoneally with O.lmg/kg PD98059 separately;they were injected twice a week for excessive 4 weeks. Thereafter, the mice were sacrificed and analyzed for the presence of lung metastases by gross observation and microscopic examination. The total number of visible tumor colonies on the surface of lung specimen was scored. The result turned out that: lung metastatic colonies of various diameter and number were notice on the surface of lung specimen of different groups. The number of lung metastatic colonies each specimen ranged between 1 and 13;the diameter range betwwen 5 -6mm and millet. With the combination of number and diameter of lung metastatic colonies each specimen, lung metastatic colonies were divided into grade I, grade II, grade III, with the extent of severity increases. We found there was less grade III metastatic node in the experimental group compared to controls. Histopathologically, lung metastatic node presented as: several metastatic focus of different diameter were seen in lung tissue, cellular heterogeneity was obvious. 3. We established xenograft model of adenoid cystic carcinoma on nude mice by injecting ACC- M cell into dorsal subcutaneous tissue of nude mice, bump on doral were noticed 1 week after implantation, the volume of the bump increased gradually. Under microscope, tumor cell form solid tumor like structure, cellular heterogeneity was obvious.In the study, we found that ERK pathway inhibitor PD98059 inhibited cell proliferation of ACC-M cell in vitro, and reduced the severity of lung metastasis, implying that ERK maybe a key molecular of target therapy for adenoid cystic carcinoma of salivary gland, inhibition of ERK pathway along with other therapy may become the trend of anti-tumor treatment research.