The combination of Nutlin-3 and Tanshinone IIA promotes synergistic cytotoxicity in acute leukemic cells expressing wild-type p53 by co-regulating MDM2-P53 and the AKT/mTOR pathway

The antipsychotic drug pimozide promotes apoptosis through the RAF/ERK pathway and enhances autophagy in breast cancer cells

The antipsychotic drug pimozide has been demonstrated to inhibit cancer. However, the precise anti-cancer mechanism of pimozide remains unclear. The purpose of this study was to investigate the effects of pimozide on human MCF-7 and MDA-MB-231 breast cancer cell lines, and the potential involvement in the RAF/ERK signaling. The effects of pimozide on cells were examined by 4,5-dimethylthiazol-2-yl-3,5-diphenylformazan, wound healing, colony formation, transwell assays, and caspase activity assay. Flow cytometry and acridine orange and ethidium bromide staining were performed to assess changes in cells. Transmission electron microscopy and monodansylcadaverine staining were used to observe autophagosomes. The cyclic adenosine monophosphate was evaluated using the FRET system. Immunohistochemistry, immunofluorescence, RNA interference, and western blot investigated the expression of proteins. Mechanistically, we focus on the RAF1/ERK signaling. We detected pimozide was docked to RAF1 by Schrodinger software. Pimozide down-regulated the phosphorylation of RAF1, ERK 1/2, Bcl-2, and Bcl-xl, up-regulated Bax, and cleaved caspase-9 to induce apoptosis. Pimozide might promote autophagy by up-regulating cAMP. The enhancement of autophagy increased the conversion of LC3-I to LC3-II and down-regulated p62 expression. But mTOR signaling was not involved in promoting autophagy. The knockdown of RAF1 expression induced autophagy and apoptosis in breast cancer cells, consistent with the results of pimozide or sorafenib alone. Blocked autophagy by chloroquine resulted in the impairment of pimozide-induced apoptosis. These data showed that pimozide inhibits breast cancer by regulating the RAF/ERK signaling pathway and might activate cAMP-induced autophagy to promote apoptosis and it may be a potential drug for breast cancer treatment.

Salvia miltiorrhiza in cancer: Potential role in regulating MicroRNAs and epigenetic enzymes

MicroRNAs are small non-coding RNAs that play important roles in gene regulation by influencing the translation and longevity of various target mRNAs and the expression of various target genes as well as by modifying histones and DNA methylation of promoter sites. Consequently, when dysregulated, microRNAs are involved in the development and progression of a variety of diseases, including cancer, by affecting cell growth, proliferation, differentiation, migration, and apoptosis. Preparations from the dried root and rhizome of Salvia miltiorrhiza Bge (Lamiaceae), also known as red sage or danshen, are widely used for treating cardiovascular diseases. Accumulating data suggest that certain bioactive constituents of this plant, particularly tanshinones, have broad antitumor effects by interfering with microRNAs and epigenetic enzymes. This paper reviews the evidence for the antineoplastic activities of S. miltiorrhiza constituents by causing or promoting cell cycle arrest, apoptosis, autophagy, epithelial-mesenchymal transition, angiogenesis, and epigenetic changes to provide an outlook on their future roles in the treatment of cancer, both alone and in combination with other modalities.

Cell Survival and Cell Death at the Intersection of Autophagy and Apoptosis: Implications for Current and Future Cancer Therapeutics

Autophagy and apoptosis are functionally distinct mechanisms for cytoplasmic and cellular turnover. While these two pathways are distinct, they can also regulate each other, and central components of the apoptosis or autophagy pathway regulate both processes directly. Furthermore, several upstream stress-inducing signaling pathways can influence both autophagy and apoptosis. The crosstalk between autophagy and apoptosis has an integral role in pathological processes, including those related to cancer, homeostasis, and aging. Apoptosis is a form of programmed cell death, tightly regulated by various cellular and biochemical mechanisms, some of which have been the focus of drug discovery efforts targeting cancer therapeutics. Autophagy is a cellular degradation pathway whereby cells recycle macromolecules and organelles to generate energy when subjected to stress. Autophagy can act as either a prodeath or a prosurvival process and is both tissue and microenvironment specific. In this review we describe five groups of proteins that are integral to the apoptosis pathway and discuss their role in regulating autophagy. We highlight several apoptosis-inducing small molecules and biologics that have been developed and advanced into the clinic and discuss their effects on autophagy. For the most part, these apoptosis-inducing compounds appear to elevate autophagy activity. Under certain circumstances autophagy demonstrates cytoprotective functions and is overactivated in response to chemo- or radiotherapy which can lead to drug resistance, representing a clinical obstacle for successful cancer treatment. Thus, targeting the autophagy pathway in combination with apoptosis-inducing compounds may be a promising strategy for cancer therapy.

Tanshinone IIA: A Review of its Anticancer Effects

Tanshinone IIA (Tan IIA) is a pharmacologically lipophilic active constituent isolated from the roots and rhizomes of the Chinese medicinal herb Salvia miltiorrhiza Bunge (Danshen). Tan IIA is currently used in China and other neighboring countries to treat patients with cardiovascular system, diabetes, apoplexy, arthritis, sepsis, and other diseases. Recently, it was reported that tan IIA could have a wide range of antitumor effects on several human tumor cell lines, but the research of the mechanism of tan IIA is relatively scattered in cancer. This review aimed to summarize the recent advances in the anticancer effects of tan IIA and to provide a novel perspective on clinical use of tan IIA.

Pharmacological basis of tanshinone and new insights into tanshinone as a multitarget natural product for multifaceted diseases

Drug development has long included the systematic exploration of various resources. Among these, natural products are one of the most important resources from which novel agents are developed due to the multiple pharmacologic effects of these natural products on diseases. Tanshinone, a representative natural product, is the main compound extracted from the dried root and rhizome of Salvia miltiorrhiza Bge. Research on tanshinone began in the early 1930s. With the in-depth investigation of an increasing number of identified analogs, tanshinone has demonstrated a wide variety of bioactivities and contradicted the saying, 'You can't teach an old dog new tricks'. This review is focused on the pharmacological action of tanshinone and status of research on tanshinone in recent years. The mechanism of tanshinone has also drawn much attention, with the findings of representative targets and pathways of tanshinone. The most recent studies have comprehensively shown that tanshinone can be used to treat leukemia and solid carcinoma, protect against cardiovascular and cerebrovascular diseases, and alleviate liver- and kidney-related diseases, among its other effects. Multiple signaling pathways, including antiproliferative, antiapoptotic, anti-inflammatory, and antioxidative stress pathways, are involved in its actions.

Inhibition of EGFR Signaling and Activation of Mitochondrial Apoptosis Contribute to Tanshinone IIA-Mediated Tumor Suppression in Non-Small Cell Lung Cancer Cells

Background

Deregulation of epidermal growth factor receptor (EGFR) signaling plays a critical role in non-small cell lung cancer (NSCLC) tumorigenesis. The natural product Tanshinone IIA (Tan IIA) exhibits significant anti-tumor effect in various human cancers, however, the mechanism remains elusive.

Methods

The inhibitory effect of Tan IIA NSCLC cells was determined by MTS and soft agar assays. The activation of EGFR signaling and the protein level of myeloid cell leukemia 1 (Mcl-1) were examined by immunoblot (IB), immunohistochemical staining (IHC), and ubiquitination analysis. The in vivo anti-tumor effect was validated by the xenograft mouse model.

Results

Tan IIA inhibits NSCLC cells through suppression of EGFR signaling. Tan IIA decreases cell viability and colony formation in EGFR wild type and activating mutant cell lines. The IB data further confirmed that Tan IIA suppresses EGFR phosphorylation time- and dose-dependently. Tan IIA destabilizes Mcl-1 and shortens the half-life. Ubiquitination analysis showed that treatment with Tan IIA promotes Mcl-1 ubiquitination and degradation. Further study showed that the downregulation of EGFR-Akt signaling is required for Tan IIA-induced Mcl-1 reduction. Ectopic overexpression of constitutively activated Akt1 compromised these antitumor efficacies in Tan IIA-treated NSCLC cells. Finally, Tan IIA inhibited the in vivo tumor growth.

Conclusion

Our data indicate that Tan IIA acts as an EGFR signaling inhibitor, and targeting EGFR-Akt-Mcl1 axis could provide a new option for NSCLC treatment.

Helping the Released Guardian: Drug Combinations for Supporting the Anticancer Activity of HDM2 (MDM2) Antagonists

The protein p53, known as the “Guardian of the Genome”, plays an important role in maintaining DNA integrity, providing protection against cancer-promoting mutations. Dysfunction of p53 is observed in almost every cancer, with 50% of cases bearing loss-of-function mutations/deletions in the TP53 gene. In the remaining 50% of cases the overexpression of HDM2 (mouse double minute 2, human homolog) protein, which is a natural inhibitor of p53, is the most common way of keeping p53 inactive. Disruption of HDM2-p53 interaction with the use of HDM2 antagonists leads to the release of p53 and expression of its target genes, engaged in the induction of cell cycle arrest, DNA repair, senescence, and apoptosis. The induction of apoptosis, however, is restricted to only a handful of p53^wt cells, and, generally, cancer cells treated with HDM2 antagonists are not efficiently eliminated. For this reason, HDM2 antagonists were tested in combinations with multiple other therapeutics in a search for synergy that would enhance the cancer eradication. This manuscript aims at reviewing the recent progress in developing strategies of combined cancer treatment with the use of HDM2 antagonists.