Foxp3 expressing regulatory T (Treg) cells, as the central negative regulator of adaptive immune system, are essential to suppress immune response and maintain immune homeostasis. However, the function of Treg cells is frequently compromised in autoimmunity and hyper-activated in infections and tumor microenvironments. Thus, manipulating Treg cells becomes a promising therapeutic strategy for treating various diseases. Here we reported that inhibition of Cdk8/Cdk19 activity by small molecule inhibitors CCT251921 or Senexin A greatly promoted the differentiation of Treg cells and the expression of Treg signature genes, such as Foxp3, CTLA4, PD-1, and GITR. Mechanistically, we found that the augmented Treg cell differentiation was due to sensitized TGF-β signaling by Cdk8/Cdk19 inhibition, which was associated with attenuation of IFN-γ-Stat1 signaling and enhancement of phosphorylated Smad2/3. Importantly, treatment with Cdk8/Cdk19 inhibitor CCT251921 significantly increased Treg population and ameliorated autoimmune symptoms in an experimental autoimmune encephalomyelitis (EAE) model. Taken together, our study reveals a novel role of Cdk8/Cdk19 in Treg cell differentiation and provides a potential target for Treg cell based therapeutics.

Oridonin, an active diterpenoid isolated from Rabdosia rubescens, has been widely used for treatment of various types of cancer. It has been shown that oridonin produced an antiproliferative effect in a lung cancer cell line in vitro. However, the antitumor effects of oridonin in lung cancer cells xenograft mice were poorly understood. The aim of the current study was to investigate the antitumor activity of oridonin in vivo and the molecular mechanisms mediating this antitumor efficacy. The human A549 and NCI-H292 non-small cell lung cancer cell lines were transferred to nude mice for the establishment of xenograft models. The results showed that oridonin (10, 20, 40 mg/kg, intraperitoneally) treatment for 28 days significantly decreased tumor volume and induced tumor growth inhibition in both A549 and NCI-H292 xenograft mice. Furthermore, oridonin promoted apoptosis by increasing terminal dUTP nick end labeling-positive cells as well as the ratio of Bax/Bcl-2 in xenograft mice. In addition, chronic oridonin administration inhibited mammalian target of rapamycin (mTORC1) activity by reduction of p-mTOR and p-p70s6k levels, suggesting that the increased apoptosis triggered by oridonin administration was associated with the downregulation of mTORC1 activity. Moreover, inhibition of mTORC1 by rapamycin (2 mg/kg, intraperitoneally) enhanced the anticancer activity of oridonin in mice xenograft models. These findings indicate that treatment with oridonin exhibited antitumor actions through induction of apoptotic response by inhibition of mTORC1 function. Our results also proposed the potential that inhibition of mTORC1 might be an effective target for increasing the therapeutic outcome in lung cancer patients treated with oridonin.

Transforming growth factor-β (TGF-β) plays a critical role in regulating cell growth and differentiation. Epithelial to mesenchymal transition (EMT) induced by TGF-β promotes cancer cell migration, invasion, and proliferation. Pirfenidone (5-methyl-1-phenyl-2(1 H)-pyridone, PFD), an approved drug for treating pulmonary and renal fibrosis, is a potent TGF-β inhibitor and found reduced incidence of lung cancer and alleviated renal function decline. However, whether PFD plays a role in controlling renal cancer progression is largely unknown. In the present study, we demonstrated that high TGF-β1 expression was negatively associated with ten-year overall survival of patients with renal cancer. Functionally, blockade of TGF-β signaling with PFD significantly suppressed the progression of renal cancer in a murine model. Mechanistically, we revealed that PFD significantly decreased the expression and secretion of TGF-β both in vitro and in vivo tumor mouse model, which further prevented TGF-β-induced EMT and thus cell proliferation, migration, and invasion. Importantly, the downregulation of TGF-β upon PFD treatment shaped the immunosuppressive tumor microenvironment by limiting the recruitment of tumor-infiltrating MDSCs. Therefore, our study demonstrated that PFD prevents renal cancer progression by inhibiting TGF-β production of cancer cells and downstream signaling pathway, which might be presented as a therapeutic adjuvant for renal cancer.

In spite of initially promising responses, 5-year recurrence after photodynamic therapy (PDT) sustains high level and an increase in PDT effectiveness is needed. It has been demonstrated that gap junctional intercellular communication (GJIC) formed by Connexin (Cx)43 could improve the transfer of “death signal” between cells, thereby causing the enhancement of cytotoxicity of chemotherapeutics and suicide gene therapy. Nevertheless, whether Cx43-composed GJIC has an effect on PDT phototoxicity remains unknown. This study showed that Cx43-formed GJIC could improve PDT phototoxicity to tumor cells in vitro and in vivo. Specifically, Cx43-formed GJIC under the condition of high cellular density could improve PDT phototoxicity in Cx43-transfected HeLa cells and Cx43-expressing U87 glioma cells. This effect was remarkably inhibited when Cx43 was not expressed or Cx43-formed GJ channels were prohibited. Additionally, the presence of Cx43-mediated GJIC could decrease the mean RTV and tumor weights of xenografts after Photofrin-PDT. The improved PDT efficacy by Cx43-composed GJIC was correlated with stress signaling pathways mediated by ROS, calcium and lipid peroxide. The present study demonstrates the presence of Cx43-composed GJIC improves PDT phototoxicity and suggests that therapeutic strategies designed to upregulate the expression of Cx43 or enhance Cx43-mediated GJIC function may increase the sensitivity of malignant cell to PDT, leading to the increment of PDT efficacy. Oppositely, factors that retard Cx43 expression or prohibit the function of Cx43-mediated GJIC may cause insensitivity of malignant cells to PDT, leading to PDT resistance.

Albumin-bound paclitaxel (abPTX) has been widely used in cancer treatment. However, dose-related side effects, such as myelosuppression, restrict its clinical application. Cell-based targeting drug delivery is a promising way to mitigate systematic side-effects and improve antitumoral efficacy. In this study, we demonstrated that reassembled abPTX could be engulfed by neutrophils in vivo and delivered to tumor site, thus improving therapeutic efficacy and mitigating myelosuppression. First, in vitro analysis confirmed that reassembling of abPTX formed uniform and stable serum albumin nanoparticles (NP-abPTX) with size of 107.5 ± 2.29 nm and reserved the ability to kill tumor cells. Second, we found that NP-abPTX could be engulfed by activated neutrophil in vitro and in vivo but do not affect neutrophils’ function, such as chemotaxis and activation. In a murine tumor model, we further proved that local radiotherapy (RT) induced inflammation activated peripheral neutrophils to capture venous infused NP-abPTX and carry them into tumor tissue. As compared to abPTX, infusion of NP-abPTX dramatically enhanced inhibition of tumor growth treated by local RT and mitigated hematotoxicity. Therefore, our study demonstrated a novel strategy to mitigate side-effects and to improve tumor killing efficacy of abPTX through neutrophil-mediated targeting drug delivery.