Advances in preclinical small molecules for the treatment of NSCLC

Epigenetics in non-small cell lung cancer: from basics to therapeutics

Lung cancer remains the number one cause of cancer-related deaths worldwide with 221,200 estimated new cases and 158,040 estimated deaths in 2015. Approximately 80% of cases are non-small cell lung cancer (NSCLC). The diagnosis is usually made at an advanced stage where the prognosis is poor and therapeutic options are limited. The evolution of lung cancer is a multistep process involving genetic, epigenetic, and environmental factor interactions that result in the dysregulation of key oncogenes and tumor suppressor genes, culminating in activation of cancer-related signaling pathways. The past decade has witnessed the discovery of multiple molecular aberrations that drive lung cancer growth, among which are epidermal growth factor receptor (EGFR) mutations and translocations involving the anaplastic lymphoma kinase (ALK) gene. This has translated into therapeutic agent developments that target these molecular alterations. The absence of targetable mutations in 50% of NSCLC cases and targeted therapy resistance development underscores the importance for developing alternative therapeutic strategies for treating lung cancer. Among these strategies, pharmacologic modulation of the epigenome has been used to treat lung cancer. Epigenetics approaches may circumvent the problem of tumor heterogeneity by affecting the expression of multiple tumor suppression genes (TSGs), halting tumor growth and survival. Moreover, it may be effective for tumors that are not driven by currently recognized druggable mutations. This review summarizes the molecular pathology of lung cancer epigenetic aberrations and discusses current efforts to target the epigenome with different pharmacological approaches. Our main focus will be on hypomethylating agents, histone deacetylase (HDAC) inhibitors, microRNA modulations, and the role of novel epigenetic biomarkers. Last, we will address the challenges that face this old-new strategy in treating lung cancer.

Glucocorticoids suppress renal cell carcinoma progression by enhancing Na,K-ATPase beta-1 subunit expression

Glucocorticoids are commonly used as palliative or chemotherapeutic clinical agents for treatment of a variety of cancers. Although steroid treatment is beneficial, the mechanisms by which steroids improve outcome in cancer patients are not well understood. Na,K-ATPase beta-subunit isoform 1 (NaK-β1) is a cell-cell adhesion molecule, and its expression is down-regulated in cancer cells undergoing epithelial-to mesenchymal-transition (EMT), a key event associated with cancer progression to metastatic disease. In this study, we performed high-throughput screening to identify small molecules that could up-regulate NaK-β1 expression in cancer cells. Compounds related to the glucocorticoids were identified as drug candidates enhancing NaK-β1 expression. Of these compounds, triamcinolone, dexamethasone, and fluorometholone were validated to increase NaK-β1 expression at the cell surface, enhance cell-cell adhesion, attenuate motility and invasiveness and induce mesenchymal to epithelial like transition of renal cell carcinoma (RCC) cells in vitro. Treatment of NaK-β1 knockdown cells with these drug candidates confirmed that these compounds mediate their effects through up-regulating NaK-β1. Furthermore, we demonstrated that these compounds attenuate tumor growth in subcutaneous RCC xenografts and reduce local invasiveness in orthotopically-implanted tumors. Our results strongly indicate that the addition of glucocorticoids in the treatment of RCC may improve outcome for RCC patients by augmenting NaK-β1 cell-cell adhesion function.

Molecular markers as therapeutic targets in lung cancer

Lung cancer is responsible for 29% of cancer deaths in the United States and has very low 5-year survival rates of approximately 11% in men and 15% in women. Although the early diagnosis of lung cancer may increase the survival rate with adequate treatment, advanced lung cancers are often metastasized and receive limited benefit from therapeutic regimens. As conventional treatments for lung cancer reach their limitations, researchers have attempted to discover novel drug therapies aimed at specific targets contributing to the progression of tumorigenesis. Recent advances in systems biology have enabled the molecular biology of lung carcinogenesis to be elucidated. Our understanding of the physiologic processes of tumor development provide a means to design more effective and specific drugs with less toxicity, thereby accelerating the delivery of new drug therapies to the patient's bedside.

YL529, a novel, orally available multikinase inhibitor, potently inhibits angiogenesis and tumour growth in preclinical models

BACKGROUND AND PURPOSE

Targeted chemotherapy using small-molecule inhibitors of angiogenesis and proliferation is a promising strategy for cancer therapy.

EXPERIMENTAL APPROACH

YL529 was developed via computer-aided drug design, de novo synthesis and high-throughput screening. The biochemical, pharmacodynamic and toxicological profiles of YL529 were investigated using kinase and cell viability assays, a mouse tumour cell-containing alginate bead model, a zebrafish angiogenesis model and several human tumour xenograft models in athymic mice.

KEY RESULTS

In vitro, YL529 selectively inhibited the activities of VEGFR2/VEGFR3 and serine/threonine kinase RAF kinase. YL529 inhibited VEGF165 -induced phosphorylation of VEGFR2, as well as the proliferation, migration, invasion and tube formation of human umbilical vascular endothelial cells. It also significantly blocked vascular formation and angiogenesis in the zebrafish model. Moreover, YL529 strongly attenuated the proliferation of A549 cells by disrupting the RAF/mitogen-activated protein (MAP) or extracellular signal-regulated kinase (Erk) kinase (MEK) kinase kinase/MAPK pathway. Oral administration of YL529 (37.5-150 mg(-1) ·kg(-1) ·day(-1) ) to nude mice bearing established tumour xenografts significantly prevented the growth (60-80%) of A549, SPC-A1, A375, OS-RC-2 and HCT116 tumours without detectable toxicity. YL529 markedly reduced microvessel density and increased tumour cell apoptosis in the tumours formed in mice inoculated with the lung cancer cells, SPC-A1 and A549, and the colon carcinoma cells, HCT116.

CONCLUSIONS AND IMPLICATIONS

YL529, an orally active multikinase inhibitor, shows therapeutic potential for solid tumours, and warrants further investigation as a possible anticancer agent.

Characterization of novel synthesized small molecular compounds against non-small cell lung cancer

BACKGROUND

With the exception of surgery, the standard platinum-based chemotherapeutic agents are the preferred treatment for non-small cell lung cancer (NSCLC); however little improvement (5-year survival) has been made. Therefore it is highly desirable to develop innovative therapeutic agents for NSCLC treatment.

METHODS

Highly enantioselective synthetic methods were developed and a broad compound library was established. Cell toxicity, cell sensitivity, cell proliferation, cell invasion, and three-dimensional colony formation assays were used to assess the anticancer potential of these compounds in non-small-cell lung cancer (NSCLC) cell lines.

RESULTS

We found that the S-form of compound PL54 (PL54S, 5-20 μM) exhibited strong anticancer activity in 5 tested NSCLC cell lines. We further synthesized a highly pure R-form enantiomer of PL54 (PL54R) and its racemate (PL54Rac) and characterized their anticancer activities. The results showed that PL54S is more potent than PL54R and PL54Rac against the tested cell lines. Furthermore, less cellular toxicity was observed in the normal human lung fibroblasts. Similarly, PL54S displayed greater anti-colony formation activity compared with PL54R and PL54Rac. The cellular sensitivity assay revealed that PL54S and PL54Rac significantly suppressed cologenic formation compared with PL54R and dimethyl sulfoxide controls (p<0.01). All PL54 compounds (5 to 20 μM) significantly inhibited cell proliferation and invasion of the A549 cell line (p<0.01). A soft agar colony formation assay revealed that PL54S and PL54Rac (10 mM), but not PL54R, significantly inhibited colony formation of tested NSCLC cells (p<0.01).

CONCLUSIONS

The stereospecific compounds may prove to be a novel technique for the treatment of NSCLC.

Novel library of selenocompounds as kinase modulators

Although the causes of cancer lie in mutations or epigenic changes at the genetic level, their molecular manifestation is the dysfunction of biochemical pathways at the protein level. The 518 protein kinases encoded by the human genome play a central role in various diseases, a fact that has encouraged extensive investigations on their biological function and three dimensional structures. Selenium (Se) is an important nutritional trace element involved in different physiological functions with antioxidative, antitumoral and chemopreventive properties. The mechanisms of action for selenocompounds as anticancer agents are not fully understood, but kinase modulation seems to be a possible pathway. Various organosulfur compounds have shown antitumoral and kinase inhibition effects but, in many cases, the replacement of sulfur by selenium improves the antitumoral effect of compounds. Although Se atom possesses a larger atomic volume and nucleophilic character than sulfur, Se can also formed interactions with aminoacids of the catalytic centers of proteins. So, we propose a novel chemical library that includes organoselenium compounds as kinase modulators. In this study thirteen selenocompounds have been evaluated at a concentration of 3 or 10 µM in a 24 kinase panel using a Caliper LabChip 3000 Drug Discover Platform. Several receptor (EGFR, IGFR1, FGFR1…) and non-receptor (Abl) kinases have been selected, as well as serine/threonine/lipid kinases (AurA, Akt, CDKs, MAPKs…) implicated in main cancer pathways: cell cycle regulation, signal transduction, angiogenesis regulation among them. The obtained results showed that two compounds presented inhibition values higher than 50% in at least four kinases and seven derivatives selectively inhibited one or two kinases. Furthermore, three compounds selectively activated IGF-1R kinase with values ranging from −98% to −211%. In conclusion, we propose that the replacement of sulfur by selenium seems to be a potential and useful strategy in the search of novel chemical compound libraries against cancer as kinase modulators.

Tailoring tyrosine kinase inhibitors to fit the lung cancer genome

Tyrosine kinase inhibitors (TKIs) have been in use as cancer therapeutics for nearly a decade, and their utility in targeting specific malignancies with defined genetic lesions has proven to be remarkably effective. Recent efforts to characterize the spectrum of genetic lesions found in non-small cell lung carcinoma (NSCLC) have provided important insights into the molecular basis of this disease and have also revealed a wide array of tyrosine kinases that might be effectively targeted for rationally designed therapies. The findings of these studies, however, also provide a cautionary tale about the limitations of single-agent therapies, which fail to account for the genetic heterogeneity and pathway redundancy that characterize advanced NSCLC. Emergence of drug resistance mechanisms to specific TKIs, such as gefitinib and erlotinib, suggests that more sophisticated chemotherapeutic paradigms that target multiple pathways at the same time will be required to effectively treat this disease.

Lung cancer therapeutics that target signaling pathways: an update

Claiming more than 150,000 lives each year, lung cancer is the deadliest cancer in the USA. First-line treatments in lung cancer include surgical resection and chemotherapy, the latter of which offers only modest survival benefits at the expense of often severe and debilitating side effects. Recent advances in elucidating the molecular biology of lung carcinogenesis have elucidated novel drug targets, and treatments are rapidly evolving into specialized agents that hone in on specific aspects of the disease. Of particular interest is blocking tumor growth by targeting the physiological processes surrounding angiogenesis, pro-tumorigenic growth factor activation, anti-apoptotic cascades and other cancer-promoting signal transduction events. This article looks at several areas of interest to lung cancer therapeutics and considers the current state of affairs surrounding the development of these therapies.

Targeting mitogen-activated protein kinase kinase (MEK) in solid tumors

The Raf-mitogen activated protein kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) protein kinase signaling cascade is an important intracellular pathway whose activation influences many fundamental cellular processes and whose aberrancy is associated with cancer cell growth. In addition to activation from within by, for example, Raf mutations, this pathway is frequently activated from above by mutated Ras or epidermal growth factor receptor (EGFR). Given the near ubiquity of derangements affecting at least part of this network in cancer, there is a strong and clear rationale for interrupting it. In recent times, in colorectal and lung cancer, Ras and EGFR mutant status have been shown to be critically important and mutually exclusive predictors of response to anti-EGFR therapies. These developments underline the importance of targeting downstream effectors, and MEK inhibition has been the subject of intense scientific and clinical research for some time now. This article reviews the current status of MEK inhibitors with regard to their clinical development.