Current Cancer Drug Targets - Volume 15, Issue 3, 2015

It is suggested that our current understanding of the role of nutrients in maintaining genomic stability might be strategically employed alongside current chemotherapy, in order to prevent the emergence of drug resistant tumors and optimize medicinal chemistry approaches.

MicroRNA-153 (miR-153) is considered to be a tumor regulator. Silencing of miR-153 expression induced apoptosis in breast cancer cells. Data on mechanism suggest that up-regulation of miR- 153 level promotes cell proliferation via the down regulation of the expression of PTEN or FOXO1, which attenuates the proliferation of cancerous cells. This study aims to identify the effect of miR-153 on the activity of chemotherapeutic and targeted agents in HCC cells and to investigate the mechanisms involved. MTT, soft agar, trans-well and flow cytometry assays were performed to examine whether miR-153 down-regulated the activity of the chemotherapeutic and targeted drugs, Sorafenib, Etoposide and Paclitaxel in HCC cells. The rate of proliferation inhibition, relative survival rates and IC50 values of each drug were calculated. Western blot and luciferase assays were performed to assess whether miR-153 modulates the expression of important genes related to cell proliferation, apoptosis or survival. Results showed that miR-153 attenuated the effect of Etoposide, Paclitaxel and Sorafenib on HepG2 cells; the IC50 value increased from 0.25±0.01μmol/L to 1.02±0.14μmol/L, 0.05±0.01μmol/L to 0.14±0.02μmol/L and from 1.09±0.15μmol/L to 5.18±0.99μmol/L, respectively. In addition, miR-153 also reduced the effect of these drugs on MHCC- 97H, MHCC-97 L and L-02 cells; and it also reduced the effects of Sorafenib, Etoposide and Paclitaxel on anchorindependent growth of HepG2 cells. Over-expression of miR-153 down-regulated the activity of Etoposide and Paclitaxel on cell cycle arrest of HepG2 cells and the effect of Sorafenib on the invasion and migration of HepG2 cells. Furthermore, overexpression of miR-153 also enhanced the growth of HepG2, MHCC-97H, MHCC-97 L and L-02 cells. Mechanisms data showed that overexpression of miR-153 down regulated the activity of luciferase reporters, p15-Luc and p21-Luc; and enhanced the protein level of pro-survival or anti-apoptosis proteins Survivin and BCL-2. These results show that overexpression of miR-153 protects HepG2 cells against the effects of these drugs via multiple mechanisms, and miR-153 may be a novel target for HCC in future diagnostic and therapeutic interventions.

Chronic inflammation plays a crucial role in cigarette smoke-related carcinogenesis. Accordingly, anti-inflammatory agents, such as nonsteroidal anti-inflammatory drugs (NSAIDs), provide a rational strategy in cancer chemoprevention. We assayed celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, and licofelone, an inhibitor of COX-1, COX-2, and 5- lipoxygenase (5-LOX), for the ability to modulate carcinogenesis in neonatal mice exposed to mainstream cigarette smoke (MCS) for 4 months and thereafter kept in filtered air for 3.5 months. A preliminary toxicity study and a chemoprevention study involved the use of 591 Swiss H mice. Exposure to MCS caused a variety of pulmonary emphysema, alveolar and bronchial epithelial hyperplasias, proliferation of blood vessels, microadenomas, adenomas and malignant tumors, as well as kidney tubular and urinary bladder papillary epithelial hyperplasias. Celecoxib (1600 mg/kg diet) and even better licofelone (960 mg/kg diet) were able to significantly attenuate the MCS-induced alterations of inflammatory nature, including pulmonary emphysema, alveolar epithelial hyperplasias and microadenomas and urinary tract hyperplastic lesions when given to mice according to a protocol that mimics an intervention in current smokers. Moreover, celecoxib attenuated the yield of lung adenomas and both NSAIDs showed some involvement in lowering the progression to cancer in the lung. Celecoxib exhibited some protective effects even when given according to a protocol involving its administration after discontinuation of exposure to MCS. However, both agents and especially celecoxib showed some hepatotoxicity and affected survival and body weight gain of mice when administered to MCS-exposed mice in the long term.

Activation of checkpoint kinase 1 (Chk1) is essential in chemoresistance of hepatocarcinoma (HCC) to 5-fluorouracil (5-FU) and other antimetabolite family of drugs. In this study, we demonstrated that PHA-767491, a dual inhibitor of two cell cycle checkpoint kinases, cell division cycle kinase 7 (Cdc7) and cyclin-dependent kinase 9 (Cdk9), has synergistic antitumor effect with 5-FU to suppress human HCC cells both in vitro and in vivo. Compared with the sole use of each agent, PHA-767491 in combination with 5-FU exhibited much stronger cytotoxicity and induced significant apoptosis manifested by remarkably increased caspase 3 activation and poly(ADP-Ribose) polymerase fragmentation in HCC cells. PHA-767491 directly counteracted the 5-FU-induced phosphorylation of Chk1, a substrate of Cdc7; and decreased the expression of the anti-apoptotic protein myeloid leukemia cell 1, a downstream target of Cdk9. In tumor tissues sectioned from nude mice HCC xenografts, administration of PHA-767491 also decreased Chk1 phosphorylation and increased in situ cell apoptosis. Our study suggests that PHA- 767491 could enhance the efficacy of 5-FU by inhibiting Chk1 phosphorylation and down-regulating Mcl1 expression through inhibition of Cdc7 and Cdk9, thus combinational administration of PHA-767491 with 5-FU could be potentially beneficial to patients with advanced and resistant HCC.

Microparticles (MPs) are released from most eukaryotic cells after the vesiculation of the plasma membrane and serve as vectors of long and short-range signaling. MPs derived from multidrug resistant (MDR) cancer cells carry molecular components of the donor cell such as nucleic acids and proteins, and can alter the activity of drug-sensitive recipient cells through the transfer of their cargo. Given the substantial role of MPs in the acquisition and dissemination of MDR, we propose that the inhibition of MP release provides a novel therapeutic approach. This study characterises the effect of a panel of molecules known to act on MP-biosynthetic pathways. We demonstrate a differential effect by these molecules on MP inhibition that appear dependent on the release of intracellular calcium stores following activation with the calcium ionophore A23187. Calpain inhibitor, PD-150606; a selective inhibitor of Rho-associated, coiled-coil containing protein kinase (ROCK), Y-27632; and the vitamin B5 derivative pantethine, inhibited MP release only upon prior activation with A23187. Calpain inhibitor II showed significant inhibition in the absence of cell activation, whereas the vitamin B5 derivatives cystamine dihydrochloride and cysteamine hydrochloride showed no effect on MP inhibition under either condition. In contrast the classical pharmacological inhibitor of MDR, the calcium channel blocker Verapamil, showed an increase in MP formation on resting cells. These results suggest a potential role for calcium in the mechanism of action for PD-150606, Y-27632 and pantethine. These molecules, together with calpain inhibitor II have shown promise as modulators of MP release and warrant consideration as potential candidates for the development of an alternative therapeutic strategy for the prevention of MP-mediated MDR in cancer.

Ovarian cancer (OC) remains the most aggressive and lethal gynecological tumor characterized by massive intraperitoneal dissemination and malignant ascites. The carcinoma cells exfoliated from the primary tumor and were further transformed in the ascites microenvironment. During this suspension process, multi-cellular spheroids are formed and these aggregates represent an invasive and chemoresistant cellular population fundamental to metastatic dissemination. Activation of EGFR signaling is involved in increased cell metastasis and decreased apoptosis of ovarian cancer. The application of EGFR Inhibition in ovarian cancer was hampered for its limited benefit as a solitary therapy. In this work, our results primarily indicated that autophagy was induced in response to EGFR specific inhibitor AG1478 in OC cell lines generated spheres and ascites primary spheroids, characterized by the elevation of LC3-II, Beclin1 and Atg5. Blockage of autophagy with 3MA notably promoted spheroid death in suspension as well as AG1478-induced cell apoptosis, suggesting a protective autophagy contribution during tumor cells in suspension or under EGFR inhibition. Consequently, inhibiting autophagy with 3MA significantly enhanced the inhibitory effect of AG1478 on tumor cell peritoneal propagation in SKOV3 i.p. xenografts model. In addition, elevated EGFR, Beclin1, and Atg5 mRNA levels were associated with decreased ovarian cancer patient survival. Together, our findings suggested that targeting autophagy held the potential to improve EGFR inhibition benefit in the treatment of ovarian cancer cells during detachment from the extra-cellular matrix (ECM), and that this combination strategy might provide a new treatment option in controlling peritoneal metastasis of ovarian cancer.

Transposable elements (TEs) are mobile DNA sequences representing a substantial fraction of most genomes. Through the creation of new genes and functions, TEs are important elements of genome plasticity and evolution. However TE insertion in human genomes may be the cause of genetic dysfunction and alteration of gene expression contributing to cancer and other human diseases. Besides the chromosome rearrangements induced by TE repeats, this mini-review shows how gene expression may be altered following TE insertion, for example by the creation of new polyadenylation sites, by the creation of new exons (exonization), by exon skipping and by other modification of alternative splicing, and also by the alteration of regulatory sequences. Through the correlation between TE mobility and the methylation status of DNA, the importance of chromatin regulation is evident in several diseases. Finally this overview ends with a brief presentation of the use of TEs as biotechnology tools for insertional mutagenesis screening and gene therapy with DNA transposons.

Introduction: Recently, an increasing number of systemic therapies with life extending capacity have become available in metastatic castration resistant prostate cancer (mCRPC) i.e. Abiraterone acetate, Enzalutamide, Sipuleucel-T, Docetaxel, Cabazitaxel and Radium-223. More compounds are currently being evaluated in promising pivotal trials (e.g. Tasquinimod, ARN-509, ODM-201, and more). Limitations of the currently available biomarkers make treatment decisions challenging. Considering the ever increasing complexity of treatment algorithms in mCRPC the current demand of research is to find and characterize biomarkers with prognostic, predictive and surrogate quality, allowing for information on clinically meaningful outcomes and on which therapy to offer patients in different and complex scenarios. Methods: A comprehensive English-language literature review was performed through PubMed to identify articles and abstract presentations of the major conferences on cancer during December 2014. Results: In this review we address established biomarkers like prostate specific antigen, lactate dehydrogenase and alkaline phosphatase. Emerging biomarkers like circulating tumor cells, androgen receptor splice variants, cancer stem cells and imaging biomarkers have also been reviewed and placed in the context of prognostic, predictive and surrogate implications in the current field of CRPC. We elaborate on the requirements of good biomarkers and discuss possible future developments of biomarkers in CRPC. Advances in knowledge of biomarkers in CRPC and thus biomarker driven therapy monitoring and up-front therapy decisions may help in the future to tailor treatment algorithms, give information on which therapy to offer and when to continue a given therapy in equivocal scenarios. This could maximize treatment benefit and minimize toxicity.

Breast cancer stem cells (BCSCs) represent a heterogeneous subpopulation of rare cells within breast cancer tumors, displaying an enhanced tumor initiating capability and underlying disease progression and therapy resistance. Unraveling their phenotypic, biological and functional profile is a major challenge in the context of diminishing patient mortality. In this review, following a brief description on how cancer stem cells (CSCs) and their microenvironment contribute to tumor preservation and heterogeneity, we summarize the current literature regarding the molecular signature of BCSCs either localized in the primary tumor or circulating in the blood of breast cancer patients. We present recent data on specific stem and epithelial-to-mesenchymal transition (EMT) markers designating the BCSC subpopulation and underline their pathogenic significance. The molecular characterization of BCSCs has promoted the design of novel therapeutic approaches targeting the BCSC subpopulation which are currently being experimentally and clinically evaluated. We highlight recent advances on the development of novel BCSC-targeting therapeutic strategies including the inhibition of cell signaling pathways, differentiation therapy, metabolic interference and nucleotide-, bio- and nano-technology based approaches. Eliminating the chemo- and radio-resistance properties of breast cancer tumor cells via BCSC-directed therapies, combined to conventional therapeutic approaches, will augment the effectiveness of breast cancer treatment and improve the clinical outcome of breast cancer patients.