Current Medicinal Chemistry - Volume 21, Issue 14, 2014

Intrinsic and acquired drug resistance of tumor cells still causes the failure of treatment regimens in advanced human cancers. It may be driven by intrinsic tumor cells features, or may also arise from micro environmental influences. Hypoxia is a microenvironment feature associated with the aggressiveness and metastasizing ability of human solid cancers. Hypoxic cancer cells overexpress Carbonic Anhydrase IX (CA IX). CA IX ensures a favorable tumor intracellular pH, while contributing to stromal acidosis, which facilitates tumor invasion and metastasis. The overexpression of CA IX is considered an epiphenomenon of the presence of hypoxic, aggressive tumor cells. Recently, a relationship between CA IX overexpression and the cancer stem cells (CSCs) population has been hypothesized. CSCs are strictly regulated by tumor hypoxia and drive a major non-mutational mechanism of cancer drug-resistance. We reviewed the current data concerning the role of CA IX overexpression in human malignancies, extending such information to the expression of the stem cells markers CD44 and nestin in solid cancers, to explore their relationship with the biological behavior of tumors. CA IX is heavily expressed in advanced tumors. A positive trend of correlation between CA IX overexpression, tumor stage/grade and poor outcome emerged. Moreover, stromal CA IX expression was associated with adverse events occurrence, maybe signaling the direct action of CA IX in directing the mesenchymal changes that favor tumor invasion; in addition, membranous/cytoplasmic co-overexpression of CA IX and stem cells markers were found in several aggressive tumors. This suggests that CA IX targeting could indirectly deplete CSCs and counteract resistance of solid cancers in the clinical setting.

Curcumin, a major component of the golden spice turmeric (Curcuma longa), has been linked with the prevention and treatment of a wide variety of cancers through modulation of multiple cell signaling pathways. Since the first report from our laboratory in 1995 that curcumin can inhibit activation of the proinflammatory transcription factor NF-κB by inhibiting the 26S proteasomal degradation of IκBα, an inhibitor of NF-κB, this yellow pigment has been shown to inhibit the protease activities of the proteasome. The carbonyl carbons of the curcumin molecule directly interact with the hydroxyl group of the amino-terminal threonine residue of the proteasomal CT-L subunit of 20S proteasome and cellular 26S proteasome. Curcumin is also a potent inhibitor of COP9 signalosome and associated kinases, casein kinase 2 and protein kinase D, all linked to the ubiquitin-proteasomal system (UPS). Curcumin can also directly inhibit ubiquitin isopeptidases, a family of deubiquitinases (DUBs) that salvage ubiquitin for reuse by the 26S proteasome system. The inhibition of this enzyme by curcumin is mediated through α,β-unsaturated ketone and two sterically accessible β-carbons. Regulation of the UPS pathway by curcumin has been linked to regulation of cancer-linked inflammatory proteins (such as COX-2 and iNOS), transcription factors (NF-κB, STAT3, Sp, AP-1, GADD153/CHOP, HIF-1α), growth factors (VEGF, HER2), apoptotic proteins (p53, Bcl-2, survivin, DNA topoisomerase II, HDAC2, p300, hTERT) and cell cycle proteins (cyclin D1, cyclin E, cyclin B, p21, p27) associated with the prevention and therapy of cancer. Interestingly, the effect of curcumin on 26S proteasome appears to be dose-dependent, as low doses (≥1 μM) increase proteasome activity whereas high doses (≤10 μM) inhibit the proteasome activity. In this review, we discuss in detail how modulation of these targets by curcumin is linked to prevention and treatment of cancer.

The efficacy of classical and molecular therapies in cancer is hampered by the occurrence of primary (intrinsic) and secondary (acquired) refractoriness of tumours to selected therapeutic regimens. Nevertheless, the increased knowledge of the genetic, molecular and metabolic mechanisms underlying cancer results in the generation of a correspondingly increasing number of druggable targets and molecular drugs. Thus, a current challenge in molecular oncology and medicinal chemistry is to cope with the increased need for modelling, both in cellular and animal systems, the genetic assets associated to cancer resistance to drugs. In this review, we summarize the current strategies for generation and analysis of in vitro and in vivo models, which may reveal useful to extract information on the molecular basis of intrinsic and acquired resistance to anticancer molecular agents.

The use of agents capable of impairing RTK function is gaining prominence for their effectiveness against the tumorigenic program driven by oncogenic RTK activity in a wide range of cancer cells. Having this valuable resource in hand for molecularly targeted anticancer therapies, it is mandatory to understand how to use these agents properly for combined treatments in order to maximize clinical efficacy. The remarkable plasticity and adaptation of cancer cells should also be taken into account, since this leads to the acquisition of “resistance” during treatment. By revisiting mechanisms of drug resistance found in cancer cells and by intercalating new emerging concepts on RTK signaling coming from cancer genome studies, this review discusses strategies aimed to enhance the effectiveness of RTK blocking agents and overcome resistance to treatment.

Since the introduction of chemotherapy in cancer therapy, development of resistance to every new therapeutic has been the universal experience. The growing understanding of cancer genomics, cancer-associated signal transduction pathways, and key protein drivers of cancer has enabled cancer biologists and medicinal chemists to develop targeted molecules to interfere with these pathways to tackle drug resistant cancers. However, to the dismay of oncologists, the clinical use of many of these tools has once again brought to the forefront the inevitable challenge of drug resistance. It is now understood that cancer resistance to different therapies involves multiple challenges that encompass the cancer cell itself as well as host physiology. This review presents small molecule inhibitors and peptides as two therapeutic approaches in anti-cancer drug development. Resistance to selected samples of these novel therapies is described in the context of cell autonomous resistance, the contributions of the tumor microenvironment, and germ line factors. For each approach, advantages and disadvantages are discussed on how to better overcome the inevitable challenge of resistance in cancer treatment.

Metastasis, also called secondary neoplastic disease, is a tumour newly formed in a site different from that of origin, as a consequence of cancer progression and dissemination largely through blood and lymphatic vessels. The ability to form metastases is the main property that distinguishes malignant from benign tumours. Treatments for metastatic cancer are similar in practice to those for primary tumours, but such treatments are mostly palliative; indeed, almost all deaths caused by solid tumours occur in the metastatic phase. Increasing evidence supports the concept that therapies for primary tumours are inadequate to treat metastasis and can even promote formation of metastases, while exerting local growth control. Furthermore, recurrent tumours, which are denoted by increased aggressiveness and therapy resistance in comparison with the primary tumour, have an increased metastatic potential. Genetic modifications occurring during tumour progression lead to substantial differences between the primary and metastatic tumours. This emphasises the importance of designing novel therapies for metastasis. In the last decade, a number of studies have contributed to the understanding of the genetic rearrangements underlying the conversion of cancer cells into the metastasis founder cells. The present article aims at reviewing recent advances in metastasis research and attempts to discuss the reasons for which the therapeutic strategies against primary tumours may not satisfactorily address their metastatic counterparts.

A number of successful systemic therapies are available for the treatment of disseminated cancers. However, tumor response is often transient, and therapy frequently fails due to emergence of resistant populations. The latter reflects the temporal and spatial heterogeneity of the tumor microenvironment as well as the evolutionary capacity of cancer phenotypes to adapt to therapeutic perturbations. Resistance to either chemotherapy and targeted agents limits the effectiveness of current cancer therapies, including those used to treat metastatic colorectal cancer (mCRC) which is one of the leading causes of cancer-related death worldwide. Resistance to therapeutic drugs can be already present at diagnosis or it can develop after treatment. These two forms of resistance are respectively called intrinsic and acquired. The identification of mechanisms of drug resistance may highlight new biomarkers useful to predict the clinical outcome or the likely responsiveness to pharmacological treatment of those metastatic CRC patients who cannot benefit from current therapeutic regimen. Moreover, the recognition of panels of biomarkers may suggest new strategies to overcome resistance by rational drug design and combination treatment. In this review, we describe molecular mechanisms of resistance to chemotherapies and targeted agents that may be relevant to colorectal cancer and the possible strategies to overcome the resistance.

A large number of indolyl-4-azaindolyl thiazoles, nortopsentin analogues, were conveniently synthesized. The antiproliferative activity of the new derivatives was examined against four human tumor cell lines with different histologic origin. Seven derivatives consistently reduced the growth of the experimental models independently of TP53 gene status and exhibited the highest activity against the malignant peritoneal mesothelioma (STO) cell line. The most active compound of this series acts as a CDK1 inhibitor, and was found to cause cell cycle arrest at G2/M phase, to induce apoptosis by preventing the phosphorylation of survivin in Thr34; and to increase the cytotoxic activity of paclitaxel in STO cells.