A novel anti-cancer agent, acetyltanshinone IIA, inhibits oestrogen receptor positive breast cancer cell growth by down-regulating the oestrogen receptor

The crosstalk between ubiquitination and endocrine therapy

Endocrine therapy (ET), also known as hormone therapy, refers to the treatment of tumors by regulating and changing the endocrine environment and hormone levels. Its related mechanism is mainly through reducing hormone levels and blocking the binding of hormones to corresponding receptors, thus blocking the signal transduction pathway to stimulate tumor growth. However, with the application of ET, some patients show resistance to ET, which is attributed to abnormal accumulation of hormone receptors (HRs) and the production of multiple mutants of HRs. The targeted degradation of abnormal accumulation protein mediated by ubiquitination is an important approach that regulates the protein level and function of intracellular proteins in eukaryotes. Here, we provide a brief description of the traditional and novel drugs available for ET in this review. Then, we introduce the link between ubiquitination and ET. In the end, we elaborate the clinical application of ET combined with ubiquitination-related molecules. KEY MESSAGES: • A brief description of the traditional and novel drugs available for endocrine therapy (ET). • The link between ubiquitination and ET. • The clinical application of ET combined with ubiquitination-related molecules.

Cyclopia extracts act as selective estrogen receptor subtype downregulators in estrogen receptor positive breast cancer cell lines: Comparison to standard of care breast cancer endocrine therapies and a selective estrogen receptor agonist and antagonist

Breast cancer is the most diagnosed type of cancer amongst women in economically developing countries and globally. Most breast cancers express estrogen receptor alpha (ERα) and are categorized as positive (ER+) breast cancer. Endocrine therapies such as, selective estrogen receptor modulators (SERMs), aromatase inhibitors (AIs), and selective estrogen receptor downregulators (SERDs) are used to treat ER+ breast cancer. However, despite their effectiveness, severe side-effects and resistance are associated with these endocrine therapies. Thus, it would be highly beneficial to develop breast cancer drugs that are as effective as current therapies, but less toxic with fewer side effects, and less likely to induce resistance. Extracts of Cyclopia species, an indigenous South African fynbos plant, have been shown to possess phenolic compounds that exhibit phytoestrogenic and chemopreventive activities against breast cancer development and progression. In the current study, three well characterized Cyclopia extracts, SM6Met, cup of tea (CoT) and P104, were examined for their abilities to modulate the levels of the estrogen receptor subtypes, estrogen receptor alpha and estrogen receptor beta (ERβ), which have been recognized as crucial to breast cancer prognosis and treatment. We showed that the Cyclopia subternata Vogel (C. subternata Vogel) extracts, SM6Met and cup of tea, but not the C. genistoides extract, P104, reduced estrogen receptor alpha protein levels while elevating estrogen receptor beta protein levels, thereby reducing the ERα:ERβ ratio in a similar manner as standard of care breast cancer endocrine therapies such as fulvestrant (selective estrogen receptor downregulator) and 4-hydroxytamoxifen (elective estrogen receptor modulator). Estrogen receptor alpha expression enhances the proliferation of breast cancer cells while estrogen receptor beta inhibits the proliferative activities of estrogen receptor alpha. We also showed that in terms of the molecular mechanisms involved all the Cyclopia extracts regulated estrogen receptor alpha and estrogen receptor beta protein levels through both transcriptional and translational, and proteasomal degradation mechanisms. Therefore, from our findings, we proffer that the C. subternata Vogel extracts, SM6Met and cup of tea, but not the C. genistoides extract, P104, selectively modulate estrogen receptor subtypes levels in a manner that generally supports inhibition of breast cancer proliferation, thereby demonstrating attributes that could be explored as potential therapeutic agents for breast cancer.

Acetyltanshinone IIA reduces the synthesis of cell cycle-related proteins by degrading p70S6K and subsequently inhibits drug-resistant lung cancer cell growth

Targeted therapies using tyrosine kinase inhibitors (TKIs) against epidermal growth factor receptor (EGFR) have improved the outcomes of patients with non-small cell lung cancer (NSCLC). However, due to genetic mutations of EGFR or activation of other oncogenic pathways, cancer cells can develop resistance to TKIs, resulting in usually temporary and reversible therapeutic effects. Therefore, new anticancer agents are urgently needed to treat drug-resistant NSCLC. In this study, we found that acetyltanshinone IIA (ATA) displayed much stronger potency than erlotinib in inhibiting the growth of drug-resistant NSCLC cells and their-derived xenograft tumors. Our analyses revealed that ATA achieved this effect by the following mechanisms. First, ATA could bind p70S6K at its ATP-binding pocket to prevent phosphorylation, and second by increasing the ubiquitination of p70S6K to cause its degradation. Since phosphorylation of S6 ribosome protein (S6RP) by p70S6K can induce protein synthesis at the ribosome, the dramatic reduction of p70S6K after ATA treatment led to great reductions of new protein synthesis on several cell cycle-related proteins including cyclin D3, aurora kinase A, polo-like kinase, cyclin B1, survivin; and reduced the levels of EGFR and MET. In addition, ATA treatment increased the levels of p53 and p21 proteins, which blocked cell cycle progression in the G1/S phase. Taken together, as ATA can effectively block multiple signaling pathways essential for protein synthesis and cell proliferation, ATA can potentially be developed into a multi-target anti-cancer agent to treat TKI-resistant NSCLC.

Tanshinone IIA potentiates the efficacy of imatinib by regulating the AKT-MDM2-P53 signaling pathway in Philadelphia chromosome-positive acute lymphoblastic leukemia

Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) is triggered by breakpoint cluster region-abelson leukemia virus (BCR/ABL) kinase. Targeting BCR/ABL kinase with tyrosine kinase inhibitors combined with chemotherapy is the standard first-line therapy for Ph+ ALL. Imatinib and dasatinib are the preferred agents for the treatment of Ph+ ALL. Dasatinib treatment can induce a faster and deeper remission than imatinib treatment; however, the side effects of dasatinib, especially the cardiovascular side effects, are markedly greater than those of imatinib. Patients will benefit from treatments that improve the efficacy of imatinib without increasing its side effects. The present study revealed that tanshinone IIA markedly potentiated the cytotoxic and apoptotic induction effects of imatinib by regulating the AKT-MDM2-P53 signaling pathway and inhibiting the anti-apoptotic proteins BCL2 and MCL1 apoptosis regulator, BCL2 family member in Ph+ ALL cell lines. In vitro studies, MTT assay, flow cytometry, western blotting and reverse transcription-quantitative PCR were performed in the present study to detect cell viability, cell apoptosis, protein expression and gene expression, respectively. In a Ph+ ALL mouse model, imatinib combined with tanshinone IIA also exhibited a synergistic effect on the reduction in leukemia burden without increasing the toxic side effects of imatinib. These results demonstrated that imatinib combined with tanshinone IIA might be a promising treatment strategy for patients with Ph+ ALL.

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.

Tanshinone IIA Inhibits Epithelial-to-Mesenchymal Transition Through Hindering β-Arrestin1 Mediated β-Catenin Signaling Pathway in Colorectal Cancer

Tanshinone IIA (Tan IIA) is a major active ingredient extracted from Salvia miltiorrhiza, which has been proved to be able to inhibit metastasis of various cancers including colorectal cancer (CRC). However, the mechanisms of anti-metastatic effect of Tan IIA on CRC are not well explored. A number of studies indicate that epithelial-to-mesenchymal transition (EMT) plays an important role in CRC metastasis, and our previous studies demonstrate that β-arrestin1could regulate EMT in CRC partly through β-catenin signaling pathway. In this work, we investigate whether Tan IIA could regulate EMT in CRC through β-arrestin1-mediated β-catenin signaling pathway both in vivo and in vitro. Our results showed that Tan IIA inhibited lung metastases of CRC cells in vivo and extended the survival time of mice with CRC. In vitro, Tan IIA increased the expression of E-cadherin, decreased the expression of Snail, N-cadherin and Vimentin, thus suppressed EMT and the migratory ability of CRC cells. Further study found that the mechanism of action of Tan IIA in regulating EMT and metastasis is associated with the suppression of β-arrestin1 expression, resulting in the increase of GSK-3β expression, reduction of β-catenin nuclear localization, thereby decreased the activity of β-catenin signaling pathway. Our data revealed a new mechanism of Tan IIA on the suppression of EMT and metastasis in CRC via β-arrestin1-mediated β-catenin signaling pathway and provided support for using Tan IIA as anti-metastatic agents in CRC.

Tanshinone IIA regulates human AML cell proliferation, cell cycle, and apoptosis through miR-497-5p/AKT3 axis

Background

The roots of Salvia miltiorrhiza are used in traditional Chinese medicine (TCM) and have high medicinal value. Tanshinone IIA (Tan IIA) is the active ingredient of Salvia miltiorrhiza which can inhibit the growth of acute leukemia cell lines in vitro, although the mechanism remains unclear.

Methods

CCK-8 assays and BrdU stain were used to evaluate cell proliferation ability. Western blot analysis was used to detect protein expression. miR-497-5p expression level was detected by using qRT-PCR, and Annexin V-FITC/propidium iodide (PI) was used to detect cell apoptosis.

Results

Here we reported that Tan IIA could inhibit cell proliferation, induce cell cycle arrest, and promote cell apoptosis in acute myeloid leukemia (AML) cells. Thus, Tan IIA had the anti-cancer activity in AML cell lines, which was likely mediated by up-regulation of miR-497-5p expression. Our data further showed that in AML cells, the same effects were observed with overexpression of miR-497-5p by a miR-497-5p mimic. We demonstrated that Tan IIA could inhibit the expression of AKT3 by up-regulating the expression of miR-497-5p. We subsequently identified that AKT3 was the direct target of miR-497-5p, and that treatment with Tan IIA obviously reversed the effect of treatment with an miR-497-5p inhibitor under harsh conditions. In turn, PCNA expression was increased and cleaved Caspase-3 was suppressed, which contributed to the growth of AML cells.

Conclusions

Our results showed that Tan IIA could inhibit cell proliferation in AML cells through miR-497-5p-mediated AKT3 downregulation pathway.

Acetyltanshinone IIA is more potent than lapatinib in inhibiting cell growth and degrading HER2 protein in drug-resistant HER2-positive breast cancer cells

High expression of human epidermal factor receptor 2 (HER2) is directly related to tumor progression, malignancy and drug resistance in HER2-positive breast cancer (HER2-PBC). The major limitation of current anti-HER2 therapies is that they cannot reduce the levels of HER2 protein. Here, we investigated the effect of acetyltanshinone IIA (ATA) in lapatinib-resistant HER2-PBC cells. Our data showed that ATA exhibited more potent effects than lapatinib against drug-resistant HER2-PBC cells in terms of (1) inhibiting cell growth, (2) reducing phosphorylated and total HER2 levels, (3) inhibiting tumor xenograft growth in nude mice, and (4) reducing HER2 protein levels in tumor xenografts. A mechanistic study revealed that ATA promoted HER2 degradation via increasing c-Cbl and CHIP-mediated HER2 ubiquitination and subsequent HER2 degradation by the proteasome or lysosome. ATA also reduced the levels of other tyrosine kinase receptors (TKRs), such as HER3, IGF-1R and MET, in lapatinib-resistant cells. Our findings suggest that direct degradation of HER2 and other TKRs can be an effective strategy for combatting drug resistance. They also indicate the potential utilization of ATA in treating breast cancer that is resistant or nonresponsive to current HER2-targeted therapies.

Pharmacological properties of tanshinones, the natural products from Salvia miltiorrhiza

Danshen (Cai, et al. 2016) is the dry root and rhizome of the herbaceous plant Salvia miltiorrhiza Bge. of family labiatae, a perennial plant that is native to China and Japan. The primary modern clinical applications of Danshen are for heart disease, chronic hepatitis, early cirrhosis, cerebral ischemia and pulmonary heart disease. Emerging evidence from cellular, animal, and clinical studies has begun to illuminate the pharmacological attributes of the primary lipophilic tanshinones from Danshen, which include tanshinone I, tanshinone II, cryptotanshinone and dihydrotanshinone, etc. Tanshinones offer the properties of anti-oxidation, anti-inflammation, antitumor, phytoestrogenic activity, vasodilation, neuroprotection, regulate metabolic function and other pharmacological advances. This chapter will review the discovery of the pharmacodynamic mechanism and pharmacokinetic studies of tanshinones and Danshen for further clinical applications.

Development of a Liposomal Formulation of Acetyltanshinone IIA for Breast Cancer Therapy

Acetyltanshinone IIA (ATA), synthesized in our group exhibiting good anti-breast cancer effects, is expected to replace the commonly used anti-ER+ breast cancer (breast cancer cells overexpressing the estrogen receptor) drug tamoxifen. To promote the clinical progress of ATA, polyethylene glycol (PEG)-modified liposomes were used to encapsulate ATA along with improving its bioavailability and in vivo anticancer efficiency. The resulting liposomal ATA exhibited a spherical shape with an average size of 188.5 nm. In vitro evaluations showed that liposomal ATA retained the anti-breast cancer efficacy of ATA while exerting much less cytotoxicity toward noncancerous cells. Significantly, pharmacokinetics analysis showed that the AUC0-24h of liposomal ATA was 59 times higher than that of free ATA, demonstrating increased bioavailability of ATA. Preclinical experiments demonstrated that liposomal ATA reduced the growth of ER-positive human breast tumor xenografts by 73% in nude mice, and the liposomal ATA exhibited a much lower level of toxicity than that of free ATA with respect to zebrafish larval mortality, body formation, and heart function during development. Moreover, 7-day and 21-day tissue toxicity levels were determined in mice by intravenous administration of a maximum dosage of liposomal ATA (120 mg/kg). The results showed no obvious tissue damage in major organs, including the heart, liver, spleen, kidney, and brain. In summary, we have developed a clinical formulation of liposomal ATA with the high bioavailability and potent efficacy for the treatment of ER-positive breast cancer.

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

P53 dysfunction has been associated with various malignant tumors, including acute leukemia. The overexpression of mouse double minute 2 (MDM2) causes the inactivation of p53 in acute leukemia. MDM2 inhibitors that activate p53 and induce apoptosis are currently being developed for potential treatment of acute leukemia. However, MDM2 inhibitors alone have limited efficacy in acute leukemia therapeutics. Combining other drugs to enhance the efficacy of MDM2 inhibitors is the thus considered as a potential treatment scheme. Here, we report that the combination of Nutlin-3 and Tanshinone IIA synergistically induces cytotoxicity, cell cycle arrest, apoptosis, and autophagic cell death, thereby imparting anti-leukemia effect in an acute leukemia cell line with wild-type p53 by effectively activating p53, inhibiting the AKT/mTOR pathway, and activating the RAF/MEK pathway. Using primary samples from acute leukemia patients, we show that the combination of Nutlin-3 plus Tanshinone IIA synergistically induces cytotoxicity by activating p53 and inhibiting the AKT/mTOR pathway. This specific combination of Nutlin-3 and Tanshinone IIA is also effective in preventing the recurrence of refractory leukemia, such as Ph+ ALL with the ABL kinase T315I mutation and AML with the FLT3-ITD mutation. Taken together, the results of this study demonstrate that the Nutlin-3 plus Tanshinone IIA combination exerts synergistic anti-leukemia effects by regulating the p53 and AKT/mTOR pathways, although further investigation is warranted. Small-molecule MDM2 antagonists plus Tanshinone IIA may thus be a promising strategy for the treatment of acute leukemia.

In vitro and in silico perspectives on estrogenicity of tanshinones from Salvia miltiorrhiza

This work aims to investigate the structure-activity relationship for binding and activation of human estrogen receptor α ligand binding domain (hERα-LBD) with tanshinones by a combination of in vitro and in silico approaches. The recombinant hERα-LBD was expressed in E. coli strain. The direct binding interactions of tanshinones with hERα-LBD and their ERα agonistic potency were investigated by fluorescence polarization (FP) and reporter gene assays, respectively. FP assay suggested that the tested tanshinones can bind to hERα-LBD as affinity ligands. Tanshinones acted as agonists of hERα as demonstrated by transactivation of estrogen response element (ERE) in transiently transfected MCF-7 cells and by molecular docking of these compounds into the hydrophobic binding pocket of hERα-LBD. Interestingly, comparison of the calculated binding energies versus Connolly solvent-excluded volume and experimental binding affinities showed a good correlation. This work may provide insight into chemical and pharmacological characterization of novel bioactive compounds from Salvia miltiorrhiza.

Anticancer effect of acid ceramidase inhibitor ceranib-2 in human breast cancer cell lines MCF-7, MDA MB-231 by the activation of SAPK/JNK, p38 MAPK apoptotic pathways, inhibition of the Akt pathway, downregulation of ERα

Acid ceramidase is the key enzyme of the ceramide metabolic pathway, which plays a vital role in regulating ceramide - sphingosine-1-phosphate rheostat. Ceramide acts as a proapoptotic molecule, but its metabolite sphingosine-1-phosphate, in contrast, signals for cell proliferation, cell survival, and angiogenesis. Acid ceramidase is highly upregulated in breast tumors and treatment with an acid ceramidase inhibitor, ceranib-2, significantly induced apoptosis in human breast cancer cell lines. However, the mechanisms underlying the induction of apoptosis remain ambiguous to date. Hence, in the present study, we have explored ceranib-2-mediated apoptotic signaling pathways in human breast cancer cell lines. MCF-7 and MDA MB-231 cells were treated with IC50 doses of ceranib-2 and tamoxifen. Nuclear changes showed the apoptotic effect of ceranib-2 in both the cell lines. Loss in the mitochondrial membrane potential was observed only in ceranib-2-treated MCF-7 cells. Ceranib-2 activated intrinsic and extrinsic apoptotic pathways in MCF-7 cells, but only the extrinsic apoptotic pathway was activated in MDA MB-231 cells. Further, ceranib-2 induced apoptosis by activating SAPK/JNK (stress-activated protein kinase/c-Jun N-terminal kinase), p38 MAPK (mitogen-activated protein kinase) apoptotic pathways and by inhibiting the Akt (antiapoptotic) pathway in both the cell lines. Most importantly, ERα (estrogen receptor-α) expression was highly downregulated after ceranib-2 treatment and a docking study predicted the highest binding affinity of ceranib-2 than tamoxifen with ERα in MCF-7 cells. Hence, ceranib-2 may have potential as a chemotherapeutic drug of breast cancer.

Nutlin-3 plus tanshinone IIA exhibits synergetic anti-leukemia effect with imatinib by reactivating p53 and inhibiting the AKT/mTOR pathway in Ph+ ALL

Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) is triggered by BCR/ABL kinase. Recent efforts focused on the development of more potent tyrosine kinase inhibitors (TKIs) that also inhibit mutant tyrosine kinases such as nilotinib and dasatinib. Although major advances in the treatment of this aggressive disease with potent inhibitors of the BCR/ABL kinases, patients in remission frequently relapse due to drug resistance possibly mediated, at least in part, by compensatory activation of growth-signaling pathways and protective feedback signaling of leukemia cells in response to TKI treatment. Continuous activation of AKT/mTOR signaling and inactivation of p53 pathway were two mechanisms of TKI resistance. Here, we reported that nutlin-3 plus tanshinone IIA significantly potentiated the cytotoxic and apoptotic induction effects of imatinib by down-regulation of the AKT/mTOR pathway and reactivating the p53 pathway deeply in Ph+ ALL cell line. In primary samples from Ph+ ALL patients, nutlin-3 plus tanshinone IIA also exhibited synergetic cytotoxic effects with imatinib. Of note, three samples from Ph+ ALL patients harboring T315I mutation also showed sensitivity to the combined treatment of imatinib, nutlin-3 plus tanshinone IIA. In Ph+ ALL mouse models, imatinib combined with nutlin-3 plus tanshinone IIA also exhibited synergetic effects on reduction in leukemia burden. These results demonstrated that nutlin-3 plus tanshinone IIA combined TKI might be a promising treatment strategy for Ph+ ALL patients.

Enhancement of the bioavailability of a novel anticancer compound (acetyltanshinone IIA) by encapsulation within mPEG-PLGA nanoparticles: a study of formulation optimization, toxicity, and pharmacokinetics

The Poly (ethylene glycol) methyl ether-block-poly (lactide-co-glycolide) (mPEG-PLGA) nanoparticles carrying acetyltanshinone IIA (ATA), a novel anti-breast cancer agent, were prepared by ultrasonic emulsion method to enhance the bioavailability and reduce the toxicity. Systematic optimization of encapsulation process was achieved using an orthogonal design. Drug efficacy analysis showed that ATA nanoparticles were as effective as free ATA against estrogen receptor positive breast cancer cells, but much less toxic towards human endothelial cells. Furthermore, in zebrafish, ATA nanoparticles displayed much lower toxicity than free ATA. More importantly, the blood concentration of ATA nanoparticles indicated by 24 hour-area under the curve (AUC_0-24h) was 10 times higher than free ATA. These results indicated the potential of ATA-loaded mPEG-PLGA nanoparticles for the delivery of ATA in a clinical formulation, and their potential for use in tumor therapy in the future.

Inhibition and inactivation of human CYP2J2: Implications in cardiac pathophysiology and opportunities in cancer therapy

Extrahepatic cytochrome P450 enzymes (CYP450) are pivotal in the metabolism of endogenous substrates and xenobiotics. CYP2J2 is a major cardiac CYP450 and primarily metabolizes polyunsaturated fatty acids such as arachidonic acid to cardioactive epoxyeicosatrienoic acids. Due to its role in endobiotic metabolism, CYP2J2 has been actively studied in recent years with the focus on its biological functions in cardiac pathophysiology. Additionally, CYP2J2 metabolizes a number of xenobiotics such as astemizole and terfenadine and is potently inhibited by danazol and telmisartan. Notably, CYP2J2 is found to be upregulated in multiple cancers. Hence a number of specific CYP2J2 inhibitors have been developed and their efficacy in inhibiting tumor progression has been actively studied. CYP2J2 inhibitor such as C26 (1-[4-(vinyl)phenyl]-4-[4-(diphenyl-hydroxymethyl)-piperidinyl]-butanone hydrochloride) caused marked reduction in tumor proliferation and migration as well as promoted apoptosis in cancer cells. In this review, we discuss the role of CYP2J2 in cardiac pathophysiology and cancer therapeutics. Additionally, we provide an update on the substrates, reversible inhibitors and irreversible inhibitors of CYP2J2. Finally, we discuss the current gaps and future directions in CYP2J2 research.

Paeoniflorin inhibits human glioma cells via STAT3 degradation by the ubiquitin-proteasome pathway

We investigated the underlying mechanism for the potent proapoptotic effect of paeoniflorin (PF) on human glioma cells in vitro, focusing on signal transducer and activator of transcription 3 (STAT3) signaling. Significant time- and dose-dependent apoptosis and inhibition of proliferation were observed in PF-treated U87 and U251 glioma cells. Expression of STAT3, its active form phosphorylated STAT3 (p-STAT3), and several downstream molecules, including HIAP, Bcl-2, cyclin D1, and Survivin, were significantly downregulated upon PF treatment. Overexpression of STAT3 induced resistance to PF, suggesting that STAT3 was a critical target of PF. Interestingly, rapid downregulation of STAT3 was consistent with its accelerated degradation, but not with its dephosphorylation or transcriptional modulation. Using specific inhibitors, we demonstrated that the prodegradation effect of PF on STAT3 was mainly through the ubiquitin-proteasome pathway rather than via lysosomal degradation. These findings indicated that PF-induced growth suppression and apoptosis in human glioma cells through the proteasome-dependent degradation of STAT3.

Role of ER-α36 in breast cancer by typical xenoestrogens

About 10 years have passed since the discovery of the estrogen receptor subtype, estrogen receptor alpha 36 (ER-α36). The relationship between cancerous cells and ER-α36 in mediating xenoestrogens (XEs) is a significant issue in the progression and treatment of breast cancer. XEs can combine with classical estrogen receptors and other receptor subtypes especially ER-α36, resulting in activation of nongenomic pathways as well as genomic pathways. Recently, most laboratories have focused on further study into the rapidly nongenomic mechanisms by overexpressing or knocking down ER-α36 in breast cancer cell lines. These rapid responses can induce the deregulation of cell cycle, and then lead to the abnormal proliferation and differentiation by regulating distinct downstream pathways. It appears that ER-α36 is a key factor in increasing risk of breast cancer. However, in several recent studies, the action mechanisms of ER-α36 by XEs in breast cancer cell lines are not always clear. In this review, we firstly summarize the expression pattern and tumor biology of ER-α36, then discuss these related estrogenic effects of ER-α36, and lastly give the predictive and prognostic value of ER-α36 as diagnostic marker by mediating typical XEs in breast cancer.

Salvianolic acid A shows selective cytotoxicity against multidrug-resistant MCF-7 breast cancer cells

Multidrug resistance (MDR) is a major cause for incurable breast cancer. Salvianolic acid A (SAA), the hydrophilic polyphenolic derivative of Salvia miltiorrhiza Bunge (Danshen/Red Sage), was examined for cytotoxicities to MDR MCF-7 human breast cancer cells and their parental counterparts. We have shown that SAA inhibited proliferation, caused cell cycle arrest at the S phase, and induced apoptosis dose dependently to the two kinds of cancer cells. However, the resistant cells were significantly susceptible to the inhibition of SAA compared with the parental cells. SAA increased the level of reactive oxygen species (ROS) by 6.2-fold in the resistant cells, whereas the level of SAA-induced ROS changed only by 1.6-fold in their parental counterparts. Thus, the data showed that the selective cytotoxicity resulted from the hypersensitivity of the resistant cells to the strongly elevated ROS by SAA. In addition, SAA-triggered apoptosis was associated with increased caspase-3 activity, disrupted mitochondrial membrane potential, downregulated Bcl-2 expression, and upregulated Bax expression in the resistant cells. Moreover, SAA downregulated the level of P-glycoprotein, which was overexpressed in the resistant cells. This indicated that SAA modulated MDR. Furthermore, SAA showed higher antitumor activity than did doxorubicin in xenografts established from the resistant cells. The present work raised a possibility that SAA might be considered a potential choice to overcome MDR for the selective susceptibility of the resistant breast cancer cells to SAA treatment.

Tanshinone IIA attenuates bleomycin-induced pulmonary fibrosis in rats

Idiopathic pulmonary fibrosis is a chronic and progressive fibrotic lung disorder with unknown etiology and a high mortality rate. Tanshinone IIA (Tan IIA) is a lipophilic diterpene extracted from the Chinese herb Salvia miltiorrhiza Bunge with diverse biological functions. The present study was conducted to evaluate the effects of Tan IIA on bleomycin (BLM)-induced pulmonary fibrosis in rats. Rats received an intraperitoneal injection of Tan IIA and normal rats were used as controls. Severe pulmonary edema, inflammation and fibrosis were observed in the BLM-treated rats and the counts of total cells, neutrophils and lymphocytes were significantly increased in the bronchoalveolar lavage fluids of those rats. These pathological changes were markedly attenuated by subsequent treatment with Tan IIA. In addition, BLM-induced increased expression of tumor necrosis factor-α, interleukin (IL)-1β, IL-6, cyclooxygenase-2, prostaglandin E2, malondialdehyde, inducible nitric oxide synthase and nitric oxide in rats, which was also suppressed by Tan IIA injection. The present findings suggest therapeutic potential of Tan IIA for pulmonary fibrosis.