Holistic anti-tumor resistance mechanism of YBX1 and its potential as a chemoresistance target in pancreatic ductal adenocarcinoma

The overall survival rate of pancreatic ductal adenocarcinoma(PDAC)is the worst among all cancers,which is mainly due to the fact that most patients are in the late tumor stage when diagnosed,lacking effective treatment options.Although targeted therapy has shown some prospects in PDAC,its efficacy is limited to patients with specific gene mutation or target gene expression.A large number of patients have no other treatment options except chemotherapy.However,the high drug resistance rate of chemotherapy for PDAC severely limits the improvement of curative effect.Therefore,determining the key factors that lead to drug resistance in PDAC is crucial to improve the prognosis of patients.Multifunctional oncoprotein Y-box binding protein 1(YBX1)may be one of such potential targets.Studies have confirmed that YBX1 is associated with the inherent behavior of a variety of cancers,such as proliferation,invasion,metastasis,and cancer cell stemness.Herein,we integrated and analyzed the resistance mechanism of YBX1 in anti-tumor therapy,and discussed its potential as a therapeutic target to reverse the chemotherapy resistance of PDAC.

Silencing the expression and function of breast cancer resistance protein in MCF-7/MX100 cells by shRNA expressing lentivirus

Overexpression of breast cancer resistance protein （ABCG2/BCRP） in cancer cells may cause tumor resistance to chemotherapeutic drugs. RNA interference （RNAi） can selectively silence the expression of a target gene of interest. In the present study, we aimed to modulate the BCRP expression and examine the functional consequence using RNAi approach. Three siRNAs （si-BCRP1, si-BCRP2 and si-BCRP3） targeting BCRP were evaluated in drug-resistant MCF-7/MX100 cells overexpressing BCRP. The BCRP expression at the mRNA and protein levels was inhibited by si-BCRP2 and si-BCRP3 over 90% and 70%, respectively. As a result, the intracellular mitoxantrone accumulation was sharply increased in MCF-7/ MX100 cells after the transfection. Furthermore, shRNA sequences bearing si-BCRP2 and siBCRP3 were cloned into lentiviral expression plasmid （pTRIPZ） to package lentivirus, and MCF-7/MX100 cells stably expressing siRNA targeted to human ABCG2/BCRP were established by lentivector-mediated gene transfer system. The stable cells exhibited an increased miotxantrone accumulation, among which the BCRP expression at the mRNA level was reduced by Lenti-BCRP2 and Lenti-BCRP3 around 72% and 56%, respectively. Moreover, the BCRP expression at the protein level was reduced by 70% and 53%, respectively. Furthermore, the cell lines were used to screen active ingredients in traditional herbal medicines in order to evaluate BCRP substrates or inhibitors. Our data suggested that the BCRP knockdown cell lines could serve as good cell models for preclinical studies.

Near infrared light triggered nitric oxide releasing platform based on upconversion nanoparticles for synergistic therapy of cancer stem-like cells

Near infrared(NIR) light-driven nitric oxide(NO) release nano-platform based on upconversion nanoparticles(UCNPs) and light sensitive NO precursor Roussin's black salt(RBS) was fabricated to generate NO upon 808 nm irradiation. The application of 808 nm laser as the excitation source could achieve better penetration depth and avoid overheating problem. The combination of UCNPs and RBS could realize the on-demand release of NO at desired time and location by simply controlling the output of NIR laser.Cellular uptake results showed that more nanoparticles were internalized in cancer stem-like cells(CSCs)rather than non-CSCs. Therefore, a synergistic cancer therapy strategy to eradicate both CSCs and nonCSCs simultaneously was developed. Traditional chemo-drug could inhibit non-CSCs but has low killing efficiency in CSCs. However, we found that the combination of NO and chemotherapy could efficiently inhibit CSCs in bulk cells, including inhibiting mammosphere formation ability, decreasing CD44^+/CD24^- subpopulation and reducing tumorigenic ability. The mechanism studies confirmed that NO could not only induce apoptosis but also increase drug sensitivity by declining drug efflux in CSCs. This UCNPsbased platform may provide a new combinatorial strategy of NO and chemotherapy to improve cancer treatment.