Nano-based Polymeric Prodrug Co-delivery System For The Treatment Of Pancreatic Cancer

Pancreatic cancer is an extremely fatal disease with an overall 5-year survival rate less than 8%.The overall survival rate of pancreatic cancer has remained virtually unchanged over the past several decades.Pancreatic cancer is not sensitive to conventional radiotherapy and chemotherapy and early detection of pancreatic cancer is challenging.Compared with monotherapy,multi-targeting combination therapy has a better therapeutic effect.However,the best combination chemotherapy up to date for pancreatic cancer only increased the average survival from 6.8 months to 11.1 months.Thus,novel multi-targeting combination therapies are urgently needed.One of the important reasons for the dismal prognosis of pancreatic cancer is the complex tumor microenvironment involving pancreatic stellate cells(PSCs).The interaction between PSCs and cancer cells facilitates tumor progression,drug resistance and metastasis.However,the existing treatments only focus on pancreatic cancer cells,ignoring the important PSC.The first part of this thesis focuses on PSC-induced pancreatic cancer drug resistance.We immortalized the PSCs derived from pancreatic cancer patients by lentiviral transfection.The immortalized PSCs achieved the ability of long-term in vitro culture.In order to evaluate the PSC-induced drug resistance and the reversal effect,co-culture models involving PSCs were established in vitro and in vivo.SN38 is an active metabolite of irinotecan and the anti-tumor effect of SN38 is significantly better than irinotecan.However,the poor solubility limited the clinical use of SN38.We found that the commercial Hedgehog(HH)pathway inhibitor Vismodegib(GDC-0449)decreased the expression of two drug resistance associated proteins induced by the coculture of PSC and cancer cells.These two proteins are Glioma associated oncogene homolog 1(GLI-1)and UDP glucuronosyltransferase 1 A(UTT1 A).As a result,GDC0449 decreased the amount of metabolized SN38 and reversed the drug resistance induced by PSC.We then developed a combination drug delivery system based on amphiphilic polymers,which released SN38 in the presence of esterase.Furthermore,the amphiphilic copolymer effectively encapsulated GDC-0449.Smaller nanoparticles and higher GDC-0449 loading contents were obtained at the same time by simply extending the chain length of the hydrophobic SN38 block.In the PSC-enriched xenograft pancreatic tumor model,the nano-based polymeric prodrug co-delivery system significantly inhibited the tumor growth and induced tumor apoptosis.Importantly,the potential therapeutic effects are closely related to the decreased expression of collagen I,α-smooth muscle actin(α-SMA)and GLI-1 in tumor tissues.Metastasis in the early stages of pancreatic cancer is responsible for the high mortality of pancreatic cancer.Over 80%of patients lost their opportunities for surgery due to metastasis.The activated PSC in pancreatic cancer microenvironment plays an important role in metastasis.We found that calcipotriol significantly reversed the state of PSC and decreased the expression of protein N-Cadherin,which is related to tumor cell metastasis mediated by PSC.The heterologous adhesion between PSCs and pancreatic cancer cells decreased with the downregulation of N-Cadherin.Calcipotriol significantly inhibited the PSC facilitated migration and invasion of tumor cells in the 2D cell migration model and the 3D tumor cell invasion model.However,the low solubility and short half-life limited the in vivo application of calcipotriol.Therefore,amphiphilic polymers PEG-PSN38 and PEG-P(SN38-ran-CHL)were synthesized to load calcipotriol.PEG-P(SN38-ran-CHL)was found to load more calcipotriol than PEG-PSN38.Furthermore,the PSC-enriched orthotropic pancreatic tumor model with high metastatic ability was developed to evaluate the anti-metastasis effect of calcipotriol loaded PEG-P(SN38-ran-CHL)NPs,and excellent metastasis inhibition ability was achieved by reducing expression of N-Cadherin.In addition,the nano-based polymeric prodrug co-delivery system increased the accumulation of SN38 by reducing the extracellular matrix in tumors.Activated PSCs in the pancreatic cancer microenvironment play an important role in drug resistance and metastasis of pancreatic cancer.Two nano-based polymeric SN38 prodrug co-delivery systems were synthesized to encapsulate GDC-0449 and calcipotriol respectively for the combination therapy of pancreatic cancer.We also report the mechanism findings for the first time that PSCs induced the inactivation of SN38 through HH pathway,and calcipotriol inhibited the metastasis by downregulating N-Cadherin in PSCs.Based on the tumor-promoting effects of PSCs,we designed and synthesized amphiphilic polymer drug delivery systems,providing innovative theories and in-depth experimental explorations for the multi-targeting synergistic treatments of pancreatic cancer.