Perifosine selectively induces cell cycle block and modulates retinoblastoma and E2F1 protein levels in p53 mutated leukemic cell lines

Overcoming of Microenvironment Protection on Primary Chronic Lymphocytic Leukemia Cells after Treatment with BTK and MDM2 Pharmacological Inhibitors

In B-chronic lymphocytic leukemia (B-CLL), the interaction between leukemic cells and the microenvironment promotes tumor cell survival. The Bruton’s tyrosine kinase (BTK) inhibitor ibrutinib is one of the first-in-class molecules for the treatment of B-CLL patients; however, the emerging mechanisms of resistance to ibrutinib call for new therapeutic strategies. The purpose of the current study was to investigate the ability of ibrutinib plus the MDM2-inhibitor nutlin-3 to counteract the tumor microenvironment protective effect. We observed that primary B-CLL cells cultivated in microenvironment mimicking conditions were protected from apoptosis by the up-regulation of c-MYC and of p53. In the same setting, combined treatments with ibrutinib plus nutlin-3 led to significantly higher levels of apoptosis compared to the single treatments, counteracting the c-MYC up-regulation. Moreover, the combination induced high p53 levels and a significant dissipation of the mitochondrial membrane potential, together with BAX cleavage in the more active p18 form and phospho-BAD down-regulation, that are key components of the mitochondrial apoptotic pathway, enhancing the apoptosis level. Our findings propose a new therapeutic strategy to overcome the tumor microenvironment protection involved in B-CLL resistance to drugs, with possible clinical implications also for other hematologic and solid tumors for which ibrutinib is considered a therapeutic option.

Alkylphospholipids are Signal Transduction Modulators with Potential for Anticancer Therapy

BACKGROUND

Alkylphospholipids (APLs) are synthetically derived from cell membrane components, which they target and thus modify cellular signalling and cause diverse effects. This study reviews the mechanism of action of anticancer, antiprotozoal, antibacterial and antiviral activities of ALPs, as well as their clinical use.

METHODS

A literature search was used as the basis of this review.

RESULTS

ALPs target lipid rafts and alter phospholipase D and C signalling cascades, which in turn will modulate the PI3K/Akt/mTOR and RAS/RAF/MEK/ERK pathways. By feedback coupling, the SAPK/JNK signalling chain is also affected. These changes lead to a G2/M phase cell cycle arrest and subsequently induce programmed cell death. The available knowledge on inhibition of AKT phosphorylation, mTOR phosphorylation and Raf down-regulation renders ALPs as attractive candidates for modern medical treatment, which is based on individualized diagnosis and therapy. Corresponding to their unusual profile of activities, their side effects result from cholinomimetic activity mainly and focus on the gastrointestinal tract. These aspects together with their bone marrow sparing features render APCs well suited for modern combination therapy. Although the clinical success has been limited in cancer diseases so far, the use of miltefosine against leishmaniosis is leading the way to better understanding their optimized use.

CONCLUSION

Recent synthetic programs generate congeners with the increased therapeutic ratio, liposomal formulations, as well as diapeutic (or theranostic) derivatives with optimized properties. It is anticipated that these innovative modifications will pave the way for the further successful development of ALPs.

LIM and SH3 protein 1 knockdown suppresses proliferation and metastasis of colorectal carcinoma cells via inhibition of the mitogen-activated protein kinase signaling pathway

LIM and SH3 protein 1 (Lasp-1), a focal adhesion protein, serves a critical role in the regulation of cell proliferation and migration. The role of Lasp-1, as well as the intracellular signaling pathways involved in metastasis and progression of colorectal carcinoma, remains unclear. In the present study, the regulatory effect of Lasp-1 and the underlying molecular mechanism involved in migration and invasion of colorectal carcinoma were investigated. RNA interference and overexpression in SW480 cells were performed to elucidate the role of Lasp-1. Reverse transcription-quantitative polymerase chain reaction, western blotting and immunofluorescence were conducted to determine the mRNA and protein levels of Lasp-1 and extracellular-signal-regulated kinase 1/2 (ERK1/2) in SW480 cells as well as tumor and adjacent normal tissues obtained from 20 patients with colorectal carcinoma. Furthermore, a cell proliferation assay, flow cytometric analysis, and cell migration and invasion assays were performed to examine the effect of Lasp-1 on cell growth. The results of the present study demonstrated that Lasp-1 and ERK1/2 were upregulated in tumor tissue compared with adjacent normal colorectal mucosa. Cell-based in vitro assays demonstrated that Lasp-1 knockdown suppressed the expression and activation of ERK1/2, whereas Lasp-1 overexpression resulted in ERK1/2 upregulation. Additionally, Lasp-1 knockdown inhibited cell proliferation, migration, and invasion and induced cellular apoptosis and G₀/G₁ cell-cycle arrest. The results of the present study indicate that Lasp-1 serves a critical role in the progression of colorectal carcinoma regulating the activation of the mitogen-activated protein kinase signaling pathway.

Ibrutinib synergizes with MDM-2 inhibitors in promoting cytotoxicity in B chronic lymphocytic leukemia

OBJECTIVE

The aim of this study was to investigate the anti-leukemic activity of the Bruton tyrosine kinase inhibitor Ibrutinib in combination with the small molecule MDM-2 inhibitor Nutlin-3 in preclinical models.

METHODS

The potential efficacy of the Ibrutinib/Nutlin-3 combination was evaluated in vitro in a panel of B leukemic cell lines (EHEB, JVM-2, JVM-3, MEC-1, MEC-2) and in primary B-chronic lymphocytic leukemia (B-CLL) patient samples, by assessing cell viability, cell cycle profile, apoptosis and intracellular pathway modulations. Validation of the combination therapy was assessed in a B leukemic xenograft mouse model.

RESULTS

Ibrutinib exhibited variable anti-leukemic activity in vitro and the combination with Nutlin-3 synergistically enhanced the induction of apoptosis independently from the p53 status. Indeed, the Ibrutinib/Nutlin-3 combination was effective in promoting cytotoxicity also in primary B-CLL samples carrying 17p13 deletion and/or TP53 mutations, already in therapy with Ibrutinib. Molecular analyses performed on both B-leukemic cell lines as well as on primary B-CLL samples, while confirming the switch-off of the MAPK and PI3K pro-survival pathways by Ibrutinib, indicated that the synergism of action with Nutlin-3 was independent by p53 pathway and was accompanied by the activation of the DNA damage cascade signaling through the phosphorylation of the histone protein H2A.X. This observation was confirmed also in the JVM-2 B leukemic xenograft mouse model.

CONCLUSIONS

Taken together, our data emphasize that the Ibrutinib/Nutlin-3 combination merits to be further evaluated as a therapeutic option for B-CLL.

d-3-Deoxy-dioctanoylphosphatidylinositol induces cytotoxicity in human MCF-7 breast cancer cells via a mechanism that involves downregulation of the D-type cyclin-retinoblastoma pathway

Phosphatidylinositol analogs (PIAs) were originally designed to bind competitively to the Akt PH domain and prevent membrane translocation and activation. d-3-Deoxy-dioctanoylphosphatidylinositol (d-3-deoxy-diC₈PI), but not compounds with altered inositol stereochemistry (e.g., l-3-deoxy-diC₈PI and l-3,5-dideoxy-diC₈PI), is cytotoxic. However, high resolution NMR field cycling relaxometry shows that both cytotoxic and non-toxic PIAs bind to the Akt1 PH domain at the site occupied by the cytotoxic alkylphospholipid perifosine. This suggests that another mechanism for cytotoxicity must account for the difference in efficacy of the synthetic short-chain PIAs. In MCF-7 breast cancer cells, with little constitutively active Akt, d-3-deoxy-diC₈PI (but not l-compounds) decreases viability concomitant with increased cleavage of PARP and caspase 9, indicative of apoptosis. d-3-Deoxy-diC₈PI also induces a decrease in endogenous levels of cyclins D1 and D3 and blocks downstream retinoblastoma protein phosphorylation. siRNA-mediated depletion of cyclin D1, but not cyclin D3, reduces MCF-7 cell proliferation. Thus, growth arrest and cytotoxicity induced by the soluble d-3-deoxy-diC₈PI occur by a mechanism that involves downregulation of the D-type cyclin-pRb pathway independent of its interaction with Akt. This ability to downregulate D-type cyclins contributes, at least in part, to the anti-proliferative activity of d-3-deoxy-diC₈PI and may be a common feature of other cytotoxic phospholipids.

Reduced expression of the retinoblastoma protein shows that the related signaling pathway is essential for mediating the antineoplastic activity of erufosine

Erufosine is a new antineoplastic agent of the group of alkylphosphocholines, which interferes with signal transduction and induces apoptosis in various leukemic and tumor cell lines. The present study was designed to examine for the first time the mechanism of resistance to erufosine in malignant cells with permanently reduced expression of the retinoblastoma (Rb) protein. Bearing in mind the high number of malignancies with reduced level of this tumor-suppressor, this investigation was deemed important for using erufosine, alone or in combination, in patients with compromised RB1 gene expression. For this purpose, clones of the leukemic T-cell line SKW-3 were used, which had been engineered to constantly express differently low Rb levels. The alkylphosphocholine induced apoptosis, stimulated the expression of the cyclin dependent kinase inhibitor p27^Kip1 and inhibited the synthesis of cyclin D3, thereby causing a G₂ phase cell cycle arrest and death of cells with wild type Rb expression. In contrast, Rb-deficiency impeded the changes induced by eru-fosine in the expression of these proteins and abrogated the induction of G₂ arrest, which was correlated with reduced antiproliferative and anticlonogenic activities of the compound. In conclusion, analysis of our results showed for the first time that the Rb signaling pathway is essential for mediating the antineoplastic activity of erufosine and its efficacy in patients with malignant diseases may be predicted by determining the Rb status.

Perifosine--a new option in treatment of acute myeloid leukemia?

INTRODUCTION

Perifosine is a novel targeted oral Akt inhibitor. In preclinical leukemia models, perifosine has an independent cytotoxic potential but also synergizes well with other rationally selected targeted agents. The evidence from clinical trials supporting the use of perifosine in the therapy of leukemias is limited. The optimal dose and schedule have yet to be defined. However, given its favorable toxicity profile and mechanism of action, the therapeutic potential of perifosine should be evaluated in well-designed clinical trials.

AREAS COVERED

The role of the phosphatidylinositol-3 kinase (PI3K)/Akt zpathway in normal cells, cancer and leukemias is discussed. The mechanism of action of perifosine and the basic information on the development and chemical properties are summarized. The evidence from in vivo and in vitro studies is presented. The efficacy and side effect profile are summarized.

EXPERT OPINION

The safety and tolerability profile of perifosine are satisfactory. The evidence from clinical trials in patients with leukemias is very limited. The preclinical data are encouraging. Perifosine has the potential to play a role in the treatment of leukemias in the future. Its role needs to be confirmed in clinical trials.

Alkylphospholipids deregulate cholesterol metabolism and induce cell-cycle arrest and autophagy in U-87 MG glioblastoma cells

Glioblastoma is the most common malignant primary brain tumour in adults and one of the most lethal of all cancers. Growing evidence suggests that human tumours undergo abnormal lipid metabolism, characterised by an alteration in the mechanisms that regulate cholesterol homeostasis. We have investigated the effect that different antitumoural alkylphospholipids (APLs) exert upon cholesterol metabolism in the U-87 MG glioblastoma cell line. APLs altered cholesterol homeostasis by interfering with its transport from the plasma membrane to the endoplasmic reticulum (ER), thus hindering its esterification. At the same time they stimulated the synthesis of cholesterol from radiolabelled acetate and its internalisation from low-density lipoproteins (LDLs), inducing both 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) and LDL receptor (LDLR) genes. Fluorescent microscopy revealed that these effects promoted the accumulation of intracellular cholesterol. Filipin staining demonstrated that this accumulation was not confined to the late endosome/lysosome (LE/LY) compartment since it did not colocalise with LAMP2 lysosomal marker. Furthermore, APLs inhibited cell growth, producing arrest at the G2/M phase. We also used transmission electron microscopy (TEM) to investigate ultrastructural alterations induced by APLs and found an abundant presence of autophagic vesicles and autolysosomes in treated cells, indicating the induction of autophagy. Thus our findings clearly demonstrate that antitumoural APLs interfere with the proliferation of the glioblastoma cell line via a complex mechanism involving cholesterol metabolism, cell-cycle arrest or autophagy. Knowledge of the interrelationship between these processes is fundamental to our understanding of tumoural response and may facilitate the development of novel therapeutics to improve treatment of glioblastoma and other types of cancer.

Perifosine in renal cell carcinoma

INTRODUCTION

Perifosine is an oral alkylphospholipid which has recently been assessed clinically in patients with advanced renal cell carcinoma (RCC). Perifosine acts primarily by attenuating the activation of Akt by preventing its pleckstrin homology (PH) domain-dependent localization to the cell membrane.

AREAS COVERED

This review summarizes the therapeutic landscape of RCC including the proposed role of perifosine in patients with advanced RCC. The mechanism of action, pharmacodynamics, pharmacokinetics, clinical efficacy in RCC and safety of perifosine are all addressed as well.

EXPERT OPINION

Although perifosine has clear clinical activity in RCC, it is not superior to currently available agents and therefore does not appear worthy of further clinical development in RCC as a single agent. Given the observed efficacy and mild toxicity, however, perifosine may have a role in RCC therapy given in combination with other molecularly targeted agents.

Two phase 2 trials of the novel Akt inhibitor perifosine in patients with advanced renal cell carcinoma after progression on vascular endothelial growth factor-targeted therapy

BACKGROUND

The clinical activity of allosteric inhibitors of mammalian target of rapamycin (mTOR) inhibitors in renal cell carcinoma (RCC) may be limited by upstream activation of phosphatidylinositol 3 (PI3)-kinase/Akt resulting from mTOR1 inhibition. On the basis of this rationale, 2 independent phase 2 trials (Perifosine 228 and 231) were conducted to assess the efficacy and safety of the novel Akt inhibitor perifosine in patients with advanced RCC who had failed on previous vascular endothelial growth factor (VEGF)-targeted therapy.

METHODS

In the Perifosine 228 trial, 24 patients with advanced RCC received oral perifosine (100 mg daily). Perifosine 231 enrolled 2 groups that received daily oral perifosine (100 mg daily): Group A comprised 32 patients who had received no prior mTOR inhibitor, and Group B comprised 18 patients who had received 1 prior mTOR inhibitor.

RESULTS

In the Perifosine 228 trial, 1 patient achieved a partial response (objective response rate, 4%; 95% confidence interval, 0.7%-20%), and 11 patients (46%) had stable disease as their best response. The median progression-free survival was 14.2 weeks (95% confidence interval, 7.7-21.6 weeks). In the Perifosine 231 trial, 5 patients achieved a partial response (objective response rate, 10%; 95% confidence interval, 4.5%-22.2%) and 16 patients (32%) had stable disease as their best response. The median progression-free survival was 14 weeks (95% confidence interval, 12.9, 20.7 weeks). Overall, perifosine was well tolerated, and there were very few grade 3 and 4 events. The most common toxicities included nausea, diarrhea, musculoskeletal pain, and fatigue.

CONCLUSIONS

Although perifosine demonstrated activity in patients with advanced RCC after failure on VEGF-targeted therapy, its activity was not superior to currently available second-line agents. Nonetheless, perifosine may be worthy of further study in RCC in combination with other currently available therapies.