Novel apoptosis inducing agents in cancer therapy

Merkel Cell Carcinoma: An Immunotherapy Fairy-Tale?

Merkel cell carcinoma (MCC) is a rare, highly aggressive, neuroendocrine cutaneous tumor. The incidence of MCC is growing worldwide, and the disease-related mortality is about three-fold higher than melanoma. Since a few years ago, very little has been known about this disease, and chemotherapy has been the standard of care. Nowadays, new discoveries about the pathophysiology of this neoplasm and the introduction of immunotherapy allowed to completely rewrite the history of these patients. In this review, we provide a summary of the most important changes in the management of Merkel cell carcinoma, with a focus on immunotherapy and a landscape of future treatment strategies.

Treatment of Advanced Merkel Cell Carcinoma: Current Therapeutic Options and Novel Immunotherapy Approaches

Advanced Merkel cell carcinoma (MCC) is a very aggressive, rare neuroendocrine tumor of the skin with a high frequency of locoregional recurrence and metastasis, and a high mortality rate. Surgical resection, sentinel lymph node biopsy, and radiotherapy represent the gold standard of treatment in patients with localized disease, while chemotherapy has a significant role in the treatment of advanced disease. However, no definitive evidence on the survival impact of radiotherapy in the advanced stages has been provided to date, and response to chemotherapy remains brief in the majority of cases, indicating an urgent need for alternative approaches. Biological and genome sequencing studies have implicated multiple molecular pathways in MCC, thus leading to the development of new agents that target angiogenic factors, anti-apoptosis molecules, poly-ADP ribose polymerase, intracellular signal proteins such as the PI3K/AKT/mTOR pathway, and peptide receptors such as somatostatin receptors. More recently, immunotherapy agents such as avelumab, pembrolizumab, and nivolumab, which act by blocking the programmed cell-death (PD)-1/PD-L1 immune checkpoint, have shown promising results, especially in the advanced setting, and should now be considered standard of care for metastatic MCC. Current research is focusing on developing new immunotherapeutic strategies, identifying predictive biomarker to aid in the selection of patients responsive to immunotherapy, and defining combination approaches to increase efficacy in refractory patients.

Targeting ceramide metabolism in obesity

Obesity is a major health concern that increases the risk for insulin resistance, type 2 diabetes (T2D), and cardiovascular disease. Thus, an enormous research effort has been invested into understanding how obesity-associated dyslipidemia and obesity-induced alterations in lipid metabolism increase the risk for these diseases. Accordingly, it has been proposed that the accumulation of lipid metabolites in organs such as the liver, skeletal muscle, and heart is critical to these obesity-induced pathologies. Ceramide is one such lipid metabolite that accumulates in tissues in response to obesity, and both pharmacological and genetic strategies that reduce tissue ceramide levels yield salutary actions on overall metabolic health. We will review herein why ceramide accumulates in tissues during obesity and how an increase in intracellular ceramide impacts cellular signaling and function as well as potential mechanisms by which reducing intracellular ceramide levels improves insulin resistance, T2D, atherosclerosis, and heart failure. Because a reduction in skeletal muscle ceramide levels is frequently associated with improvements in insulin sensitivity in humans, the beneficial findings reported for reducing ceramides in preclinical studies may have clinical application in humans. Therefore, modulating ceramide metabolism may be a novel, exciting target for preventing and/or treating obesity-related diseases.

Gracilaria edulis extract induces apoptosis and inhibits tumor in Ehrlich ascites tumor cells in vivo

BACKGROUND

Marine environment is inestimable for their chemical and biological diversity and therefore is an extraordinary resource for the discovery of new anticancer drugs. Recent development in elucidation of the mechanism and therapeutic action of natural products helped to evaluate for their potential activity.

METHODS

We evaluated Gracilaria edulis J. Ag (Brown algae), for its antitumor potential against the Ehrlich ascites tumor (EAT) in vivo and in vitro. Cytotoxicity evaluation of Ethanol Extract of Gracilaria edulis (EEGE) using EAT cells showed significant activity. In vitro studies indicated that EEGE cytotoxicity to EAT cells is mediated through its ability to produce reactive oxygen species (ROS) and therefore decreasing intracellular glutathione (GSH) levels may be attributed to oxidative stress.

RESULTS

Apoptotic parameters including Annexin-V positive cells, increased levels of DNA fragmentation and increased caspase-2, caspase-3 and caspase-9 activities indicated the mechanism might be by inducing apoptosis. Intraperitoneally administration of EEGE to EAT-bearing mice helped to increase the lifespan of the animals significantly inhibited tumor growth and increased survival of mice. Extensive hematology, biochemistry and histopathological analysis of liver and kidney indicated that daily doses of EEGE up to 300 mg/kg for 35 days are well tolerated and did not cause hematotoxicity nor renal or hepatotoxicity.

CONCLUSION

Comprehensive antitumor analysis in animal model and in Ehrlich Ascites Tumor cells was done including biochemical, and pathological evaluations indicate antitumor activity of the extract and non toxic in vivo. It was evident that the mechanism explains the apoptotic activity of the algae extract.

Growth inhibition and pro-apoptotic activity of violacein in Ehrlich ascites tumor

The continuing threat to biodiversity lends urgency to the need of identification of sustainable source of natural products. This is not so much trouble if there is a microbial source of the compound. Herein, violacein, a natural indolic pigment extracted from Chromobacterium violaceum, was evaluated for its antitumoral potential against the Ehrlich ascites tumor (EAT) in vivo and in vitro. Evaluation of violacein cytotoxicity using different endpoints indicated that EAT cells were twofold (IC(50)=5.0 microM) more sensitive to the compound than normal human peripheral blood lymphocytes. In vitro studies indicated that violacein cytotoxicity to EAT cells is mediated by a rapid (8-12h) production of reactive oxygen species (ROS) and a decrease in intracellular GSH levels, probably due to oxidative stress. Additionally, apoptosis was primarily induced, as demonstrated by an increase in Annexin-V positive cells, concurrently with increased levels of DNA fragmentation and increased caspase-2, caspase-9 and caspase-3 activities up to 4.5-, 6.0- and 5.5-fold, respectively, after 72 h of treatment. Moreover, doses of 0.1 and 1.0 microg kg(-1) violacein, administered intraperitoneally (i.p.) to EAT-bearing mice throughout the lifespan of the animals significantly inhibited tumor growth and increased survival of mice. In view of these results, a 35-day toxicity study was conducted in vivo. Complete hematology, biochemistry (ALT, AST and creatinine levels) and histopathological analysis of liver and kidney indicated that daily doses of violacein up to 1000 microg kg(-1) for 35 days are well tolerated and did not cause hematotoxicity nor renal or hepatotoxicity when administered i.p. to mice. Altogether, these results indicate that violacein causes oxidative stress and an imbalance in the antioxidant defense machinery of cells culminating in apoptotic cell death. Furthermore, this is the first report of its antitumor activity in vivo, which occurs in the absence of toxicity to major organs.

G3139 (Genasense) in patients with advanced merkel cell carcinoma

OBJECTIVES

Merkel cell carcinoma (MCC) is a rare, aggressive neuroendocrine malignancy of the skin. Preclinical studies have identified up-regulation of the critical antiapoptosis gene bcl-2 in MCC. We conducted a multicenter phase II trial of the novel bcl-2 antisense agent (G3139, Genasense) in patients with advanced MCC.

METHODS

Twelve patients (9 men, 3 women) with histologically confirmed metastatic or regionally recurrent MCC were enrolled. Ten patients (83%) had received prior chemotherapy. Eight patients (67%) had Karnofsky performance status of 90 to 100. Patients received continuous IV infusion of G3139 (7 mg/kg/d) via central venous access in an outpatient setting for 14 days, followed by a 7-day rest period. Response was assessed at 6-week intervals. Patients were allowed to continue therapy until unacceptable toxicity or disease progression.

RESULTS

No objective responses were observed. The best response was stable disease in 3 patients and progressive disease in 9 patients. A median of 4 doses per patient (total 46 doses) was administered. Dose delays and/or reductions were required in 6 patients. One patient developed grade 4 lymphopenia. One patient developed grade 3 renal failure characterized by grade 3-elevated creatinine and grade 4 hyperkalemia. Other grade 3 events included cytopenia (n = 5), aspartate aminotransferase/alanine aminotranferease elevation (n = 3), hypophosphatemia (n = 2), and pain (n = 1). The most frequent grade 1 to 2 toxicities were elevated creatinine, ALT elevation, hypokalemia, lymphopenia, and fatigue.

CONCLUSIONS

Bcl-2 antisense therapy (G3139) was well tolerated among patients with advanced MCC. Although probable antitumor activity was documented in 1 patient, no objective responses per Response Evaluation Criteria in Solid Tumors criteria were observed.

Molecular imaging of cell death in vivo by a novel small molecule probe

Apoptosis has a role in many medical disorders, therefore assessment of apoptosis in vivo can be highly useful for diagnosis, follow-up and evaluation of treatment efficacy. ApoSense is a novel technology, comprising low molecular-weight probes, specifically designed for imaging of cell death in vivo. In the current study we present targeting and imaging of cell death both in vitro and in vivo, utilizing NST-732, a member of the ApoSense family, comprising a fluorophore and a fluorine atom, for both fluorescent and future positron emission tomography (PET) studies using an ¹⁸F label, respectively. In vitro, NST-732 manifested selective and rapid accumulation within various cell types undergoing apoptosis. Its uptake was blocked by caspase inhibition, and occurred from the early stages of the apoptotic process, in parallel to binding of Annexin-V, caspase activation and alterations in mitochondrial membrane potential. In vivo, NST-732 manifested selective uptake into cells undergoing cell-death in several clinically-relevant models in rodents: (i) Cell-death induced in lymphoma by irradiation; (ii) Renal ischemia/reperfusion; (iii) Cerebral stroke. Uptake of NST-732 was well-correlated with histopathological assessment of cell-death. NST-732 therefore represents a novel class of small-molecule detectors of apoptosis, with potential useful applications in imaging of the cell death process both in vitro and in vivo.

Biological profile of new apoptotic agents based on 2,4-pyrido[2,3-d]pyrimidine derivatives

In order to obtain less toxic antitumoral compounds we have looked for novel compounds with anticancer activity based on proapoptotic mechanisms. The compounds studied in this work are derivatives of bicyclic aromatic systems like pyrido[2,3-d]pyrimidines. The potential antitumoral activity of the compounds was evaluated in vitro by examining their cytotoxic effects against human breast, colon, and bladder cancer lines (MD-MBA-231, HT-29, and T-24). The data indicate that HC-6 is a potent anticancer drug showing dose-dependent cytostatic and proapoptotic effects through activation of two different signaling pathways namely a pathway leading to cell cycle arrest and a transcription-independent route leading to rapid apoptosis.

New drugs in prostate cancer

PURPOSE OF REVIEW

The survival of hormone-refractory metastatic prostate cancer patients has improved with the use of docetaxel-based chemotherapy. The survival benefits, however, are modest suggesting that rationally designed therapeutic approaches are needed. We discuss recent developments in the therapeutic approach to advanced metastatic hormone-refractory prostate cancer, including molecularly targeted therapy, signal transduction inhibitors, stem-cell targeted therapy, anti-angiogenic compounds, vaccines and immunomodulating agents, differentiation agents, cytotoxics, and pro-apoptotic agents.

RECENT FINDINGS

Over 200 compounds have entered clinical development for use in advanced prostate cancer, alone or in combination with cytotoxic agents such as docetaxel, or in other combinations. This article will review the results of emerging targets since the approval of docetaxel in 2004, concentrating on some of those compounds that, in our opinion, have the greatest potential and rationale for use.

SUMMARY

The growing field of targeted molecular therapy of prostate cancer has opened up numerous opportunities for therapeutic impact. Knowledge of the molecular determinants of progression, relapse after local therapy, chemotherapeutic resistance, and hormone refractoriness remains essential in the rational design of clinical trials of these agents. Given the complexity, heterogeneity, and crosstalk of molecular pathways and the molecular lesions in prostate cancer, combination or sequential therapy may be a necessary step towards significant therapeutic progress. Novel translational clinical trial methodologies may assist in a more rapid identification of active compounds at biologically active doses for phase-III testing.