Correlation Of RET Mutation With Expression Of CTn,PCT,PTHR1,ATF4 In Medullary Thyroid Carcinoma

Background:Thyroid cancer?TC?is the most common endocrine malignant tumor.In recent years,its incidence has increased rapidly.Medullary thyroid carcinoma?MTC?derived from the malignant proliferation of parafolular cells?C cells?accounts for3%¹0%of TC.MTC can be classified into Hereditary medullary thyroid carcinoma?HMTC?and Sporadic medullary thyroid carcinoma?SMTC?.The malignant degree of MTC is between differentiated and anaplastic thyroid cancer.It has the characteristics of strong invasiveness,easy metastasis,recurrence and poor prognosis.At present,ultrasound-guided cell biopsy is the first choice for TC diagnosis,but its value in preoperative diagnosis of MTC is limited.Moreover,MTC is not sensitive to chemoradiotherapy and ¹³¹I iodine treatment,and surgery is still the main means of clinical MTC treatment.Therefore,in view of the limitations of early diagnosis and treatment of MTC,seeking specific molecular markers is of great significance for the diagnosis and treatment of MTC.RET and RAS gene mutations are important genetic changes of MTC and play a key role in the occurrence and development of MTC.Currently,they have become important molecular markers and targets for MTC diagnosis and treatment.CTn?calcitonin?and PCT?procalcitonin?are polypeptides secreted by parafilar cells,and CTn is a major marker of MTC diagnosis and recurrence monitoring.The expressions of PTHR1?parathyroid hormone receptor 1?and ATF4?transcriptional activator 4?were upregulated in various malignant tumor tissues and correlated with tumor progression and prognosis.However,the relationship between protein expression of PCT,PTHR1 and ATF4 and clinicopathological parameters,as well as the correlation between RET mutation and protein expression of CTn,PCT,PTHR1 and ATF4,has not been explored in MTC tissue.Objective:The aim of the present study was to investigate the RET,HRAS mutations and the expression of CTn,PCT,PTHR1 and ATF4 in SMTC tissues and its clinical significance,and preliminarily study the correlation between RET mutations and the expression of CTn,PCT,PTHR1 and ATF4,so as to provide reference for the diagnosis,prognosis evaluation and targeted therapy of MTC.Methods:Sixty-four patients with SMTC diagnosed pathologically in Gansu Cancer Hospital from January 2007 to December 2018 were collected,and 55 patients of nodular goiter and 35 patients of normal thyroid tissue were collected as control.RET and HRAS mutations were detected by the method of PCR amplification product direct sequencing,and the expressions of CTn,PCT,PTHR1 and ATF4 proteins were detected by immunohistochemical SP method.Results:1.The mutation rate of RET gene in SMTC patients was 37.5%?24/64?,and the mutation rate of M918T site was higher to 18.8%?12/64?.However,no RET mutations were detected in nodular goiter and normal thyroid tissue.Correlation analysis showed that RET mutations were associated with tumor size,lymph node metastasis and capsule invasion?P<0.05?.Meanwhile,no HRAS mutations were detected in MTC,nodular goiter and normal thyroid tissue.2.The positive rates of CTn and PCT in SMTC tissues were 90.6%?58/64?and67.2%?43/64?,respectively,which were higher than 78.2%?43/55?,47.3%?26/55?in the nodular goitre group,and 68.6%?24/35?,37.1%?13/35?in the normal thyroid group.The expressions of both was related to tumor size and lymph node metastasis?P<0.05?.Meanwhile,the intensity of CTn expression was positively correlated with RET mutation?r=0.507,P=0.000?,while the expression of PCT was not associated with RET mutation?P>0.05?.3.The positive rate of PTHR1 in SMTC tissues was 81.3%?52/64?,which was significantly higher than 69.1%?38/55?in nodular goiter group and 60.0%?21/35?in normal thyroid group,and its expression was only related to tumor size?P<0.05?.The intensity of PTHR1 expression was positively correlated with RET mutation?r=0.364,P=0.003?.4.The positive rates of ATF4 in SMTC,nodular goiter and normal thyroid tissues were 43.8%?28/64?,72.7%?40/55?and 34.3%?12/35?,respectively.The expression of ATF4 was related to tumor size and lymph node metastasis?P<0.05?.The expression of ATF4 was negatively correlated with RET mutation?r=-0.293,P=0.019?.Conclusions:1.Detection of RET mutations is beneficial to the diagnosis,differential diagnosis and risk grading of SMTC for benign and malignant thyroid tumors.2.CTn and PCT were highly expressed in SMTC tissues.CTn,as a tumor marker of MTC,its expression intensity is related to RET mutation.Simultaneously,PCT can be used as an important molecular biological marker for SMTC and has guiding value in evaluating prognosis.3.Increased PTHR1 expression and decreased ATF4 expression may play an important role in the occurrence and progression of SMTC,both of which are related to RET mutation.However,whether the two can be used as specific molecular markers of SMTC requires further study.