Background: Programmed death ligand-1(PD-L1) functions as a negative mediator of immune response through different pathways in anti-tumor immunity. Recent studies have reported that PD-L1 plays a pivotal role in the function of regulatory T-cells (Tregs). Although increases in FOXP3+ Tregs infiltration and PD-L1 expression have been revealed in several cancers, their correlation with soft tissue sarcoma remains unknown. Methods: We included 163 cases of soft tissue sarcoma who were diagnosed and underwent extensive and radical resection at the Sun Yat-sen University Cancer Center, Guangzhou, China, from 2000-2010. PD-L1 and FOXP3 expression was evaluated by immunohistochemistry. Correlation between their expressions and associations with clinicopathological features were studied. Results: Among 163 STS samples, 19 (11.7%) exhibited PD-L1 positivity, and 41 (25.2%) cases expressed high FOXP3+ Treg infiltration. Significant correlation between PD-L1 expression and FOXP3+Treg infiltration in STS was identified (r=0.450, p<0.001). In univariate analysis, PD-L1 expression was significantly associated with high tumor grade and the age of patients, while the presence of FOXP3+ in tumor infiltrating Tregs was significantly associated with the age of patients, high tumor stage, higher tumor grade and tumor depth. Multivariate analysis revealed PD-L1 and FOXP3 as independent prognostic indicators significantly associated with OS and DFS. Conclusions: Our study revealed that PD-L1 and FOXP3+Tregs may work synergistically in promoting immune evasion of the tumors in soft tissue sarcoma. A combined strategy to block PD-L1/PD-1 with simultaneous depletion of Tregs may show promise in enhancing the therapeutic efficacy of these patients.
Purpose: Resistance to chemotherapeutic drugs in nasopharyngeal carcinoma(NPC) remains a major obstacle of clinical therapy. To address the issue, screening for natural low-toxicity products as chemosensitizers has become a promising strategy for cancer therapy. In this study, we investigated chemosensitizing effects of cardamonin (CM), a plant-derived chalcone, on cisplatin (DPP)-resistant NPC cells, and explored the molecular mechanism for its antitumor activity. Methods: The chemotherapeutic e cacy of cardamonin, cisplatin and their combination in cisplatinresistant NPC cells were analyzed using MTT assay, apoptosis assay, and cell cycle analysis. Real-time PCR, western blotting, and cell transfection analysis were performed to assess the synergistic inhibitory action of cardamonin supplemented with cisplatin on Wnt/β-catenin/ABCG2 signaling. The effect of cardamonin on ABCG2 drug e ux function was analyzed by doxorubicin accumulation assay. A CNE2/DPP nude mouse model was used to determine the combinatorial effects of cardamonin on tumor growth in vivo. Results: Cardamonin increased cisplatin-induced cytotoxicity, accompanied by induction of apoptosis and cell cycle arrest in DPP-resistant NPC cells. Moreover, cardamonin could synergized with cisplatin to downregulate β-catenin, c-Myc, and ABCG2. Speci cally, cardamonin inhibited Wnt/β-catenin/ABCG2 signaling through c-Myc-mediated transcription inactivation, thereby suppressing the expression of ABCG2 in cisplatin-resistant NPC cells. These ndings were con rmed in vivo, wherein cardamonin treatment with cisplatin resulted in reduced tumor growth in a CNE2/DPP xenograft animal model. Conclusions: Taken together, our data rstly demonstrated that cardamonin increased chemosensitivity of nasopharyngeal cancer cells to cisplatin through inactivation of Wnt/β-catenin/ABCG2 signaling, more speci cally by inhibition of β-catenin/ABCG2 signaling through c-Myc-mediated transcriptional inactivation, thereby downregulation of ABCG2 and reversal of cisplatin resistance. Thus, in addition to its chemotherapeutic potential, cardamonin may serve as a useful chemosensitizer to conventional chemotherapeutic drugs in the treatment of nasopharyngeal carcinoma.
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