Establishment Of Ectopic Model Of Poorly Differentiated Thyroid Carcinoma In Athymic Nude Mice And Testing Of Chemosensitivity In Vivo And In Vitro

[Background] Poorly differentiated thyroid carcinoma (PDTC) and anaplastic (undifferentiated) thyroid carcinoma (ATC) are the most aggressive cancers in head and neck region. The patients have extremely poor prognosis though treated with combined surgery, radiotherapy and chemotherapy. For progressive growth, high distant metastasis and mortality rate, it is difficult to conduct prospective random control clinical trials. No standard treatment plan and chemotherapy regimen for patients with PDTC and ATC until now. Local recurrence and distant metastasis are the common fatal causes for most patients. New chemotherapy drugs especially the molecular targeted drugs give us a new hope to achieve local control and prevent distant metastasis. Various phaseⅠ／Ⅱclinical trials are ongoing abroad.[Objectives] There are three goals to achieve in this study. The first one is to develop an ectopic model of PDTC in athymic nude mice for chemosensitivity testing. The second is to evaluate the in vivo effects of sorafenib and liposome doxorubicin on the ectopic nude mice model of PDTC. The third is to investigate the sensitivity of antitumor drugs on thyroid cancer cells in vitro with 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT) and adenosine triphosphate-tumor chemosensitivity assay (ATP-TCA) methods.[Methods] Fresh surgical specimens of 6 thyroid carcinoma patients were implanted subcutaneous in athymic nude mice to establish the ectopic model of thyroid cancer. The ectopic model get stable after consecutive passages and immunohistochemistry (IHC) method was used to study the changes of several important proteins for tumor proliferation and metastasis. Then sorafenib and liposome doxorubicin were used to treat the ectopic model of PDTC in nude mice. The tumor growth were recorded and therapeutic effects were evaluated. At last the chemosensitivity were investigated in vitro and sensitive drugs were identified with MTT and ATP-TCA methods.[Results] The nude mice ectopic models of 2 cases PDTC and 1 case ATC were successfully established. One mouse model with PDTC could achieve 100% xenograft growth after 10 passages. No significant changes were seen in the expressing level of important proteins for tumor growth and signal conducting thus the model was suitable for mouse chemotherapy experiment. Three xenografts with papillary thyroid carcinoma were absorbed and no model was established. Sorafenib and liposome doxorubicin exerted significant antitumor activity in the ectopic xenograft model of PDTC. The mice were randomized into seven groups:blank control (A), reagent control(B), single liposome doxorubicin group(C), single sorafenib group(D), combined group with low dosage of sorafenib(E), combined group with medium dosage of sorafenib(F), combined group with high dosage of sorafenib(G). The tumor volumes of seven groups at the end of treatment were 1274.13±393.76mm3,1060.00±469.05mm3,726.76±488.22mm3, 451.54±97.75mm3,518.37±164.44mm3,310.51±210.53mm3, and 228.44±129.21 mm3, respectively. The tumor weights of the seven groups were 1.13±0.42g,0.91±0.39g, 0.78±0.45g,0.55±0.17g,0.52±0.19g,0.34±0.21g, and 0.19±0.09g, respectively. The tumor inhibition rates of group C to G were 30.8%,40.8%,42.3%,62.9%, and 72.6%, respectively. Group G had a significant higher inhibition rate compared with other groups except group F(P=0.357). Group F had better effects than group C (P=0.001) but not group D (P=0.192). The mean tumor weights of all treatment groups were lower than that of the blank control group. No mice died in the treatment groups and the mice body weights in group G had a significant decline compared with other treatment groups. Sorafenib showed varying sensitivity in vitro to papillary thyroid cancer (PTC), PDTC and ATC cells with MTT assay. Single agent vincristine(VCR), gemcitabine(GEM) and combined cisplatin(DDP) plus paclitaxel(PTX) had high sensitivities in vitro to all 3 PDTC and ATC cells with ATP-TCA method.[Conclusions] PDTC and ATC have a higher successful rate for ectopic xenograft in athymic nude mice than PTC. The mice model of PDTC grows stable after consecutive passages and is fit for chemosensitivity testing. Liposome doxorubicin and sorafenib exhibit significant antitumor activity to the ectopic PDTC mouse model in vivo no matter single agent or in combination. Combined group with medium dosage of sorafenib had a better therapeutic and less side effects compared with other groups. Both MTT and ATP-TCA could identify the sensitive antiumor drugs in vitro and the latter is probably more effective and promising. The complicated tumor chemosensitivity testing results proved diverse heterogeneity in PDTC and ATC. ATP chemosensitivity-assay in vitro directed therapy might be a useful tool to determining the optimized chemotheapeutic drugs or drug combination in the individual patient.