Rapamycin enhanced the antitumor effects of doxorubicin in myelogenous leukemia K562 cells by downregulating the mTOR/p70S6K pathway

Silencing RPL8 inhibits the progression of hepatocellular carcinoma by down-regulating the mTORC1 signalling pathway

This study aimed to explore the role of ribosomal protein L8 (RPL8) in controlling hepatocellular carcinoma (LIHC) development. We measured RPL8 expression, apoptosis, cell viability, proliferation, migration, invasion, glucose uptake, lactate production, and the ATP/ADP ratio of LIHC cells to investigate the effect of RPL8 on LIHC. Bioinformatic analysis was employed to analyse RPL8 expression and its potential mechanism in LIHC. RPL8 was upregulated in LIHC tissues and cells. RPL8 silencing accelerated apoptosis and suppressed viability, growth, and movement of LIHC cells. Additionally, RPL8 silencing inhibited glycolysis in LIHC cells. Bioinformatic analysis revealed that RPL8 is regulated by the upstream transcription factor upstream stimulating factor 1 (USF1) and activates the mTORC1 signalling pathway. USF1 overexpression eliminated the inhibitory effect of RPL8 silencing in LIHC cells. RPL8 overexpression increased cell growth, movement, and glycolysis in LIHC. However, inhibition of the mTORC1 signalling pathway eliminated the effect of RPL8 overexpression on LIHC cells. In conclusion, RPL8 may affect LIHC progression by regulating the mTORC1 signalling pathway.

Rapamycin-induced autophagy in osteosarcoma cells is mediated via the biglycan/Wnt/β-catenin signaling axis

Biglycan is a class I secreted small leucine-rich proteoglycan (SLRP), which regulates signaling pathways connected to bone pathologies. Autophagy is a vital catabolic process with a dual role in cancer progression. Here, we show that biglycan inhibits autophagy in two osteosarcoma cell lines (P ≤ 0.001), while rapamycin-induced autophagy decreases biglycan expression in MG63 osteosarcoma cells and abrogates the biglycan-induced cell growth increase (P ≤ 0.001). Rapamycin also inhibits β-catenin translocation to the nucleus, inhibiting the Wnt pathway (P ≤ 0.001) and reducing biglycan's colocalization with the Wnt coreceptor LRP6 (P ≤ 0.05). Furthermore, biglycan exhibits protective effects against the chemotherapeutic drug doxorubicin in MG63 OS cells through an autophagy-dependent manner (P ≤ 0.05). Cotreatment of these cells with rapamycin and doxorubicin enhances cells response to doxorubicin by decreasing biglycan (P ≤ 0.001) and β-catenin (P ≤ 0.05) expression. Biglycan deficiency leads to increased caspase-3 activation (P ≤ 0.05), suggesting increased apoptosis of biglycan-deficient cells treated with doxorubicin. Computational models of LRP6 and biglycan complexes suggest that biglycan changes the receptor's ability to interact with other signaling molecules by affecting the interdomain bending angles in the receptor structure. Biglycan binding to LRP6 activates the Wnt pathway and β-catenin nuclear translocation by disrupting β-catenin degradation complex (P ≤ 0.01 and P ≤ 0.05). Interestingly, this mechanism is not followed in moderately differentiated, biglycan-nonexpressing U-2OS OS cells. To sum up, biglycan exhibits protective effects against the doxorubicin in MG63 OS cells by activating the Wnt signaling pathway and inhibiting autophagy.

Rapamycin Promotes the Expansion of Myeloid Cells by Increasing G-CSF Expression in Mesenchymal Stem Cells

Rapamycin, also known as sirolimus, an inhibitor of mammalian target of rapamycin (mTOR), is a regulatory kinase responsible for multiple signal transduction pathways. Although rapamycin has been widely used in treating various hematologic diseases, the effects of rapamycin are still not fully understood. Here we found that both oral and intraperitoneal administration of rapamycin led to the expansion of myeloid lineage, while intraperitoneal administration of rapamycin impaired granulocyte differentiation in mice. Rapamycin induced bone marrow mesenchymal stem cells to produce more G-CSF in vitro and in vivo, and promoted the myeloid cells expansion. Our results thus demonstrated that intraperitoneal administration of rapamycin might promote the expansion of myeloid lineage while impair myeloid cell differentiation in vivo.

Gymnema sylvestre Extract Restores the Autophagic Pathway in Human Glioblastoma Cells U87Mg

Simple Summary

The treatment of GBM is extremely difficult and complicated by the heterogeneous nature of neoplastic cells. The problems inherent in treating any central nervous system tumour are due to the anatomical complexity and the limited repair mechanisms of the surrounding unaffected tissues. The choice of the most suitable treatment for GBM depends on several factors: the location of the disease, the extent, and the nature of the tumour. The limit of this choice is mainly due to the degree of complexity of the disease and to the mechanisms of drug resistance that the neoplasm develops during the treatment. Herbal medicines and their derived phytocompounds are increasingly recognised as useful complementary treatments for cancer. Numerous clinical studies have reported the beneficial effects of herbal medicines on survival, immune modulation, and quality of life of cancer patients when used in combination with conventional therapies. In this study, we investigated all the mechanisms that control tumour cell growth after induction with Gymnema sylvestre (GS) extract and the key proteins that regulate these mechanisms in glioblastoma cells. The study is of great translational interest because the natural substances used could be proposed as natural adjuvant drugs for the treatment of glioblastoma, and therefore could act by modulating new molecular targets for the control of brain tumour cell growth.

Abstract

Glioblastoma is a brain tumour, characterised by recurrent or innate resistance to conventional chemoradiotherapy. Novel natural molecules and phyto-extracts have been proposed as adjuvants to sensitise the response to Temozolomide (TMZ). In this study, we investigated the effect of GS extract on human glioblastoma cells U87Mg. According to the IC50-values, GS extract displayed a significant cytotoxicity. This was confirmed by cell growth inhibition and alteration in metabolic activity evaluated by cell count and MTT assay. GS induced reduction in Pro-caspase 9, 3, but not PARP cleavage nor DNA fragmentation. Thus, in GS-induced cytotoxicity, cell death is not associated with apoptosis. In this context, short-term treatment of U87Mg cells with GS extract (1 mg/mL) reduced the phosphorylation levels of mTOR and of its downstream target P70 S6 kinase, highlighting the role of GS extract into autophagy induction. The activation of autophagic flux by GS extract was confirmed by Western blot analysis, which revealed the reduction in p62 and the concomitant increase in LC3B II/I ratio. Immunofluorescence evidenced the accumulation of LC3B puncta in U87Mg cells pretreated with autophagy inhibitor Bafilomycin A1. Furthermore, as main key regulators of type II programmed cell death, p53, p21 and CDK4 were also investigated and were inhibited by GS treatment. In conclusion, GS extract could be considered as an autophagy inducer in glioblastoma cells U87Mg.

Dual PI3K/mTOR inhibitor NVP‑BEZ235 decreases the proliferation of doxorubicin‑resistant K562 cells

Acute myelogenous leukemia (AML) is frequently accompanied by a poor prognosis. The majority of patients with AML will experience recurrence due to multiple drug resistance. Our previous study reported that targeting the mTOR pathway may increase cell sensitivity to doxorubicin (Doxo) and provide an improved therapeutic approach to leukemia. However, the effect and mechanism of action of NVP-BEZ235 (BEZ235), a dual inhibitor of PI3K/mTOR, on Doxo-resistant K562 cells (K562/A) is yet to be elucidated. Therefore, the aim of the present study was to investigate the effects of BEZ235 on K562/A cell proliferation. K562/A cells was investigated using CCK-8, flow cytometry and western blotting, following BEZ235 treatment. It was observed that BEZ235 significantly decreased the viability of K562/A cells. In addition, BEZ235 arrested K562/A cells at the G₀/G₁ phase, and reduced the protein expression levels of CDK4, CDK6 and cyclin D1. Apoptotic cells were more frequently detected in K562/A cells treated with BEZ235 compared with the control group (12.97±0.91% vs. 7.37±0.42%, respectively; P<0.05). Cells treated with BEZ235 exhibited downregulation of Bcl-2 and upregulation of Bax. Furthermore, BEZ235 treatment markedly decreased the activation of the PI3K/AKT/mTOR pathway and its downstream effectors. Thus, these results demonstrated that BEZ235 inhibited cell viability, induced G₀/G₁ arrest and increased apoptosis in K562/A cells, suggesting that BEZ235 may reverse Doxo resistance in leukemia cells. Therefore, targeting the PI3K/mTOR pathway may be of value as a novel therapeutic approach to leukemia.

Two Faces of Autophagy in the Struggle against Cancer

Autophagy can play a double role in cancerogenesis: it can either inhibit further development of the disease or protect cells, causing stimulation of tumour growth. This phenomenon is called "autophagy paradox", and is characterised by the features that the autophagy process provides the necessary substrates for biosynthesis to meet the cell's energy needs, and that the over-programmed activity of this process can lead to cell death through apoptosis. The fight against cancer is a difficult process due to high levels of resistance to chemotherapy and radiotherapy. More and more research is indicating that autophagy may play a very important role in the development of resistance by protecting cancer cells, which is why autophagy in cancer therapy can act as a "double-edged sword". This paper attempts to analyse the influence of autophagy and cancer stem cells on tumour development, and to compare new therapeutic strategies based on the modulation of these processes.

Activation of AMPK by Telmisartan Decreases Basal and PDGF-stimulated VSMC Proliferation via Inhibiting the mTOR/p70S6K Signaling Axis

BACKGROUND

Telmisartan, an angiotensin II type 1 receptor blocker (ARB), is widely used to treat hypertension by blocking the renin-angiotensin-aldosterone system. Although abnormal proliferation of vascular smooth muscle cells (VSMCs) is a well-established contributor to the development of various vascular diseases, such as atherosclerosis, the effect of telmisartan on VSMC proliferation and its mechanism of action have not been fully revealed. Herein, we investigated the molecular mechanism whereby telmisartan inhibits rat VSMC proliferation.

METHODS

We measured VSMC proliferation by MTT assay, and performed inhibitor studies and western blot analyses using basal and platelet-derived growth factor (PDGF)-stimulated rat VSMCs. To elucidate the role of AMP-activated protein kinase (AMPK), we introduced dominant-negative (dn)-AMPKα1 gene into VSMCs.

RESULTS

Telmisartan decreased VSMC proliferation, which was accompanied by decreased phosphorylations of mammalian target of rapamycin (mTOR) at Ser2448 (p-mTOR-Ser²⁴⁴⁸) and p70 S6 kinase (p70S6K) at Thr389 (p-p70S6K-Thr³⁸⁹) in dose- and time-dependent manners. Telmisartan dose- and time-dependently increased phosphorylation of AMPK at Thr172 (p-AMPK-Thr¹⁷²). Co-treatment with compound C, a specific AMPK inhibitor, or ectopic expression of the dn-AMPKα1 gene, significantly reversed telmisartan-inhibited VSMC proliferation, p-mTOR-Ser²⁴⁴⁸ and p-p70S6K-Thr³⁸⁹ levels. Among the ARBs tested (including losartan and fimasartan), only telmisartan increased p-AMPK-Thr¹⁷² and decreased p-mTOR-Ser²⁴⁴⁸, p-p70S6K-Thr³⁸⁹, and VSMC proliferation. Furthermore, GW9662, a specific and irreversible peroxisome proliferator-activated receptor γ (PPARγ) antagonist, did not affect any of the telmisartan-induced changes. Finally, telmisartan also exhibited inhibitory effects on VSMC proliferation by increasing p-AMPK-Thr¹⁷² and decreasing p-mTOR-Ser²⁴⁴⁸ and p-p70S6K-Thr³⁸⁹ in a PDGF-induced in vitro atherosclerosis model.

CONCLUSION

These results demonstrated that telmisartan-activated AMPK inhibited basal and PDGF-stimulated VSMC proliferation, at least in part, by downregulating the mTOR/p70S6K signaling axis in a PPARγ-independent manner. These observations suggest that telmisartan could be used to treat arterial narrowing diseases such as atherosclerosis and restenosis.

Glycol Chitosan-Docosahexaenoic Acid Liposomes for Drug Delivery: Synergistic Effect of Doxorubicin-Rapamycin in Drug-Resistant Breast Cancer

Marine ecosystems are the most prevalent ecosystems on the planet, providing a diversity of living organisms and resources. The development of nanotechnology may provide solutions for utilizing these thousands of potential compounds as marine pharmaceuticals. Here, we designed a liposomal glycol chitosan formulation to load both doxorubicin (DOX) and rapamycin (RAPA), and then evaluated its therapeutic potential in a prepared drug-resistant cell model. We explored the stability of the drug delivery system by changing the physiological conditions and characterized its physicochemical properties. The electrostatic complexation between DOX-glycol chitosan and docosahexaenoic acid RAPA-liposomes (GC-DOX/RAPA ω-liposomes) was precisely regulated, resulting in particle size of 131.3 nm and zeta potential of -14.5 mV. The well-characterized structure of GC-DOX/RAPA ω-liposomes led to high loading efficiencies of 4.1% for DOX and 6.2% for RAPA. Also, GC-DOX/RAPA ω-liposomes exhibited high colloidal stability under physiological conditions and synergistic anti-cancer effects on DOX-resistant MDA-MB-231 cells, while showing pH-sensitive drug release behavior. Our results provided a viable example of marine pharmaceuticals with therapeutic potential for treating drug-resistant tumors using an efficient and safe drug delivery system.