| BackgroundPancreatic cancer is one of the highest serious malignancy tumors in thedigestive system, it ranks the13th worldwide morbidity and accounting forthe eighth cancer deaths. Because of early invasion and metastasis,pancreatic cancer has a poor prognosis with the overall5-year survival rateof only3-5%. For another, pancreatic cancer is an innate hypoxic tumor andless sensitive to chemotherapy and radiotherapy,regarding to gemcitabine,the most effective chemotherapy drug currently, the clinical benefit rate isonly23.8%. Radiotherapy has its restriction since surrounding tissues arevulnerable to radiation. Consequently radiotherapy dosage is usuallycontrolled, so the toxicity of chemoradiotherapy remains the most concern inclinical therapy. Surgery remains the sole existing “arsenal” against thepancreatic cancer, but resection rate of the surgery is low.85-90%of patientsdiagnosed to suffer cancer might already miss the best time for surgery due to local invasion and metastasis. Though enormous effort has been made inthe past50years, anyone or combination of conventional treatment have notbeen effective. So local therapy with few injury and significant effect is ingreat needed. High intensity focused ultrasound (HIFU), a non-invasive heatthermal ablation technique for local cancer treatment, has drawn widerattention for its non-invasiveness and excellent pinpointing. Several smallsample clinical trials have applied HIFU, alone or combined withgemcitabine, to treating patients with progressive pancreatic cancer, whichexhibits good therapeutic effect, pain control, tumor shrinkage and noserious complications such as pancreatitis. But the mechanism of thesynergistic effect is still not clear, more fundamental research is needed. Inthis research, we will investigate the effects of HIFU and gemcitabine on thehuman pancreatic cancer xenografts and pancreatic cancer cell PANC-1invitro, and to explore its possible mechanisms.Research objectivePancreatic cancer xenografts in nude micewere treated with HIFU,gemcitabine or combined of them, a comparative analysis of efficacy,prognosis and outcome were concluded, and then, we also explored thechanges of invasion and metastasis behavior and its mechanism ofpancreatic cancer cell PANC-1treated by high-intensity focused ultrasound(HIFU), gemcitabine, or combined of them, and provided basic evidence forthe clinical application of HIFU combined with chemotherapy on pancreatic cancer.Research methods1. Pancreatic cancer xenografts in nude mice, built by pancreatic cancercell PANC-1, were treated with High intensity focused ultrasound (HIFU,frequency of treatment head is0.94MHz, power is40W) or gemcitabine(100mg/m2, IP) or combined of them, then randomized into four groups.Each group was treated with HIFU, gemcitabine (GEM), HIFUcombined with gemcitabine(HIFU+GEM), and control grouprespectively. After the treatment, the tumor was measured once a week,five weeks later, drawing tumor growth curve， and tumor inhibitionrate was calculated and the expression of VEGF, MVD, MMP-2andMMP-9level in tumor tissue was tested by immunohistochemistry.2. The human pancreatic carcinoma cell linePANC-1suspension onlogarithmic phase was radiated by high-intensity focusedultrasound(HIFU, the frequency of9.8MHz, power of5W) at differentradiation time (5S,10S,15S,20S,25S,30S，35S) to select the bestirradiation parameters according MTT method. The experiment cellswere divided into four groups. Each group was treated with HIFU (5W,20S), gemcitabine (GEM,45μg/ml), HIFU combined withgemcitabine(HIFU+GEM), and control group respectively.24h aftertreatment, the change of invasive and metastasis ability was tested bymigration and transwell migration, and tested the different expression of MMP-9,MMP-2using immunohistochemical and western blot.Research results1. The tumor volume in treatment groups was significantly difference(P<0.01), both of them were lower than the control arm. The greatestdifference was between the HIFU combined with gemcitabine and thecontrol group（P<0.001）.5weeks after treatment, the tumor mass ineach treatment group was significantly lower than the control group. Thetumor inhibition rates were35.22%,60.46%,69.59%in GEM group,HIFU group and HIFU+GEM group respectively. The most obviousinhibition rate was observed in HIFU+GEM group, which wassignificantly lower than HIFU or GEM group (P<0.05). The expressionof VEGF, MVD, MMP-2, MMP-9was lowest in combined group, whichwas significantly lower than HIFU group and GEM group (P<0.05).2.1). Power of5W, irradiation time20S wasthe optimum irradiationparameters with70%cell survival rate;2). Compared with control group,cell migration and invasion in each experimental group weresignificantly decreased (P<0.05), the weakest invasion and metastasisability is in the combined group, which was significantly lower thanHIFU group and GEM group (P<0.05);3). Compared with the controlgroup, the expressing of MMP-2and MMP-9was significantly lower(P<0.05) in each experimental group. The lowest expression of MMP-2and MMP-9was observed in HIFU combined GEM group, which was significantly lower than HIFU group and GEM group.Research conclusions:1. HIFU or gemcitabine can inhibit heterotopic pancreatic tumor growth,significantly delayed tumor progression, and reduce the expression ofVEGF, CD31, MMP-2, MMP-9in tumor tissue. HIFU+GEM group playthe most significant inhibition on tumor growth, and the lowest level ofexpression of each index was observed in combined group. HIFUcombined with gemcitabinemaybe the best treatment modality.2. This experiment showed HIFU and GEM both can weaken thePANC-1’s ability of invasion and metastasis in vitro, and reduce theexpression of MMP-9and MMP-2in pancreatic cancer cell. HIFUcombined with GEM decreased the ability of invasion and migration onPANC-1cell strongest,and the lowest expression of MMP-1, MMP-9was detected in this group. This suggesting that inhibition of expressionMMP-2and MMP-9may be one of the possible ways of inhibition tumorgrowth and invasion and metastasis ability after treated by HIFU andGEM.This provided more experiment data for the treatment ofpancreatic cancer under HIFU combined with gemcitabine. |
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