Combination of zoledronic acid and serine/threonine phosphatase inhibitors induces synergistic cytotoxicity and apoptosis in human breast cancer cells via inhibition of PI3K/Akt pathway

Targeting of Mevalonate-Isoprenoid Pathway in Acute Myeloid Leukemia Cells by Bisphosphonate Drugs

Metabolic reprogramming represents a hallmark of tumorigenesis to sustain survival in harsh conditions, rapid growth and metastasis in order to resist to cancer therapies. These metabolic alterations involve glucose metabolism, known as the Warburg effect, increased glutaminolysis and enhanced amino acid and lipid metabolism, especially the cholesterol biosynthesis pathway known as the mevalonate pathway and these are upregulated in several cancer types, including acute myeloid leukemia (AML). In particular, it was demonstrated that the mevalonate pathway has a pivotal role in cellular transformation. Therefore, targeting this biochemical process with drugs such as statins represents a promising therapeutic strategy to be combined with other anticancer treatments. In the last decade, several studies have revealed that amino-bisphosphonates (BP), primarily used for bone fragility disorders, also exhibit potential anti-cancer activity in leukemic cells, as well as in patients with symptomatic multiple myeloma. Indeed, these compounds inhibit the farnesyl pyrophosphate synthase, a key enzyme in the mevalonate pathway, reducing isoprenoid formation of farnesyl pyrophosphate and geranylgeranyl pyrophosphate. This, in turn, inhibits the prenylation of small Guanosine Triphosphate-binding proteins, such as Ras, Rho, Rac, Rab, which are essential for regulating cell survival membrane ruffling and trafficking, interfering with cancer key signaling events involved in clonal expansion and maturation block of progenitor cells in myeloid hematological malignancies. Thus, in this review, we discuss the recent advancements about bisphosphonates’ effects, especially zoledronate, analyzing the biochemical mechanisms and anti-tumor effects on AML model systems. Future studies will be oriented to investigate the clinical relevance and significance of BP treatment in AML, representing an attractive therapeutic strategy that could be integrated into chemotherapy.

Periplocymarin Induced Colorectal Cancer Cells Apoptosis Via Impairing PI3K/AKT Pathway

Colorectal cancer (CRC) is one of the most common cancers worldwide, and approximately one-third of CRC patients present with metastatic disease. Periplocymarin (PPM), a cardiac glycoside isolated from Periploca sepium, is a latent anticancer compound. The purpose of this study was to explore the effect of PPM on CRC cells. CRC cells were treated with PPM and cell viability was evaluated by CCK-8 assay. Flow cytometry and TUNEL staining were performed to assess cell cycle and apoptosis. Quantitative proteomics has been used to check the proteins differentially expressed by using tandem mass tag (TMT) labeling and liquid chromatography–tandem mass spectrometry. Bioinformatic analysis was undertaken to identify the biological processes that these differentially expressed proteins are involved in. Gene expression was analyzed by western blotting. The effect of PPM in vivo was primarily checked in a subcutaneous xenograft mouse model of CRC, and the gene expression of tumor was checked by histochemistry staining. PPM could inhibit the proliferation of CRC cells in a dose-dependent manner, induce cell apoptosis and promote G0/G1 cell cycle arrest. A total of 539 proteins were identified differentially expressed following PPM treatment, where among those there were 286 genes upregulated and 293 downregulated. PPM treatment caused a pro-apoptosis gene expression profile both in vivo and in vitro, and impaired PI3K/AKT signaling pathway might be involved. In addition, PPM treatment caused less detrimental effects on blood cell, hepatic and renal function in mice, and the anti-cancer effect was found exaggerated by PPM+5-FU combination treatment. PPM may perform anti-CRC effects by promoting cell apoptosis and this might be achieved by targeting PI3K/AKT pathway. PPM might be a safe and promising anti-cancer drug that needs to be further studied.

AZD3463, an IGF-1R inhibitor, suppresses breast cancer metastasis to bone via modulation of the PI3K-Akt pathway

Background

The bone-derived insulin-like growth factor I (IGF-1) and its receptor IGF-1R play a crucial role in promoting the survival and proliferation of cancer cells, and have thus been considered as prime targets for the development of novel antitumor therapeutics.

Methods

By using the MDA-MB-231BO cell line, which is the osteotropic metastatic variant of the human breast adenocarcinoma cell line MDA-MB-231, and an in vivo model of breast cancer metastasis to bone, the current study evaluated the effect of AZD3463, an IGF-1R inhibitor, used alone or in combination with zoledronic acid (ZA), on the regulation of IGF-1R associated signal pathway and treatment of bone metastases (BM). Cell proliferation and invasion were measured by methyl thiazolyl tetrazolium (MTT) and Transwell assay respectively. Apoptotic cell number was detected by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL).

Results

AZD3463 was shown to alleviate IGF-1R phosphorylation promoted by IGF-1 treatment in MDA-MB-231BO cells in a dose-dependent manner. In both the cells and the mouse model, 5 nM of AZD3463 stimulated cell apoptosis and suppressed proliferation on a level similar to that of 100 µM of ZA. Remarkably, the combined use of AZD3463 and ZA exhibited a synergistic effect and greater antitumor activity compared to when they were employed individually. Mechanistic investigations indicated that the apoptosis-inducing activity of AZD3463 could be associated to its role in the activation of the phosphoinositide 3-kinase (PI3K)-Akt signaling pathway.

Conclusions

These findings suggested that AZD3463 could serve as a promising therapeutic molecule for treating BM in breast cancer patients, particularly when applied in conjunction with ZA or other antitumor agents.

CD44 induced enhancement of phosphatase activity and calcium influx: Modifications of EGR-1 expression and cell proliferation

The purpose of this study was to investigate how CD44 impaired Akt phosphorylation, EGR-1 expression and cell proliferation. E6.1 Jurkat cells, which lack endogenous CD44 expression, were engineered to express CD44. Previously we showed that Akt is hypophosphorylated, EGR-1 expression is reduced and proliferation is impaired in CD44 expressing E6.1 Jurkat cells. The cell cycle was studied using flow cytometry and the role of calcium (Ca²⁺) in Akt phosphorylation and EGR-1 expression was investigated using Western blotting. Phosphatase activity was assessed using a commercially available kit. CD44 expressing cells showed disruption at the G₁ to S transition. Chelation of Ca²⁺ from the culture media impaired Akt phosphorylation and EGR-1 expression in both CD44 expressing cells and the open vector control. Moreover, Ni²⁺ disrupted cell proliferation in both cell types suggesting Ca²⁺ import through calcium release activated calcium channels (CRAC). Staining of cells with fura-2 AM showed significantly higher Ca²⁺ in CD44 expressing cells as compared with the vehicle control. Finally, non-calcium mediated phosphatase activity was significantly greater in CD44 expressing cells. We propose that the enhanced phosphatase activity in the CD44 cells increased the dephosphorylation rate of Akt; at the same time, the increased intracellular concentration of Ca²⁺ in the CD44 cells ensured that the phosphorylation of Akt remains intact albeit at lower concentrations as compared with the vector control. Reduced Akt phosphorylation resulted in lowered expression of EGR-1 and hence, reduced the cell proliferation rate.