Retinoids in lung cancer chemoprevention and treatment

Application of two-dimensional difference gel electrophoresis to identify protein changes between center, margin, and adjacent non-tumor tissues obtained from non-small-cell lung cancer with adenocarcinoma or squamous cell carcinoma subtype

Lung cancer is responsible for the most cancer-related mortality worldwide and the mechanism of its development is poorly understood. Proteomics has become a powerful tool offering vital knowledge related to cancer development. Using a two-dimensional difference gel electrophoresis (2D-DIGE) approach, we sought to compare tissue samples from non-small-cell lung cancer (NSCLC) patients taken from the tumor center and tumor margin. Two subtypes of NSCLC, adenocarcinoma (ADC) and squamous cell carcinoma (SCC) were compared. Data are available via ProteomeXchange with identifier PXD032736 and PXD032962 for ADC and SCC, respectively. For ADC proteins, 26 significant canonical pathways were identified, including Rho signaling pathways, a semaphorin neuronal repulsive signaling pathway, and epithelial adherens junction signaling. For SCC proteins, nine significant canonical pathways were identified, including hypoxia-inducible factor-1α signaling, thyroid hormone biosynthesis, and phagosome maturation. Proteins differentiating the tumor center and tumor margin were linked to cancer invasion and progression, including cell migration, adhesion and invasion, cytoskeletal structure, protein folding, anaerobic metabolism, tumor angiogenesis, EMC transition, epithelial adherens junctions, and inflammatory responses. In conclusion, we identified several proteins that are important for the better characterization of tumor development and molecular specificity of both lung cancer subtypes. We also identified proteins that may be important as biomarkers and/or targets for anticancer therapy.

Revealing the Potential Application of EC-Synthetic Retinoid Analogues in Anticancer Therapy

(1) Background and Aim: All-trans retinoic acid (ATRA) induces differentiation and inhibits growth of many cancer cells. However, resistance develops rapidly prompting the urgent need for new synthetic and potent derivatives. EC19 and EC23 are two synthetic retinoids with potent stem cell neuro-differentiation activity. Here, these compounds were screened for their in vitro antiproliferative and cytotoxic activity using an array of different cancer cell lines. (2) Methods: MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay, AV/PI (annexin V-fluorescein isothiocyanate (FITC)/propidium iodide (PI)), cell cycle analysis, immunocytochemistry, gene expression analysis, Western blotting, measurement of glutamate and total antioxidant concentrations were recruited. (3) Results: HepG2, Caco-2, and MCF-7 were the most sensitive cell lines; HepG2 (ATRA; 36.2, EC19; 42.2 and EC23; 0.74 µM), Caco-2 (ATRA; 58.0, EC19; 10.8 and EC23; 14.7 µM) and MCF-7 (ATRA; 99.0, EC19; 9.4 and EC23; 5.56 µM). Caco-2 cells were selected for further biochemical investigations. Isobologram analysis revealed the combined synergistic effects with 5-fluorouracil with substantial reduction in IC₅₀. All retinoids induced apoptosis but EC19 had higher potency, with significant cell cycle arrest at subG₀-G₁, -S and G₂/M phases, than ATRA and EC23. Moreover, EC19 reduced cellular metastasis in a transwell invasion assay due to overexpression of E-cadherin, retinoic acid-induced 2 (RAI2) and Werner (WRN) genes. (4) Conclusion: The present study suggests that EC-synthetic retinoids, particularly EC19, can be effective, alone or in combinations, for potential anticancer activity to colorectal cancer. Further in vivo studies are recommended to pave the way for clinical applications.

Is carrot consumption associated with a decreased risk of lung cancer? A meta-analysis of observational studies

Findings of epidemiological studies regarding the association between carrot consumption and lung cancer risk remain inconsistent. The present study aimed to summarise the current epidemiological evidence concerning carrot intake and lung cancer risk with a meta-analysis. We conducted a meta-analysis of case-control and prospective cohort studies, and searched PubMed and Embase databases from their inception to April 2018 without restriction by language. We also reviewed reference lists from included articles. Prospective cohort or case-control studies reporting OR or relative risk with the corresponding 95 % CI of the risk lung cancer for the highest compared with the lowest category of carrot intake. A total of eighteen eligible studies (seventeen case-control studies and one prospective cohort study) were included, involving 202 969 individuals and 5517 patients with lung cancer. The pooled OR of eighteen studies for lung cancer was 0·58 (95 % CI 0·45, 0·74) by comparing the highest category with the lowest category of carrot consumption. Based on subgroup analyses for the types of lung cancer, we pooled that squamous cell carcinoma (OR 0·52, 95 % CI 0·19, 1·45), small-cell carcinoma (OR 0·43, 95 % CI 0·12, 1·59), adenocarcinoma (OR 0·34, 95 % CI 0·15, 0·79), large-cell carcinoma (OR 0·40, 95 % CI 0·10, 1·57), squamous and small-cell carcinoma (OR 0·85, 95 % CI 0·45, 1·62), adenocarcinoma and large-cell carcinoma (OR 0·20, 95 % CI 0·02, 1·70) and mixed types (OR 0·61, 95 % CI 0·46, 0·81). Exclusion of any single study did not materially alter the pooled OR. Integrated epidemiological evidence from observational studies supported the hypothesis that carrot consumption may decrease the risk of lung cancer, especially for adenocarcinoma.

The Use of Chemical-Chemical Interaction and Chemical Structure to Identify New Candidate Chemicals Related to Lung Cancer

Lung cancer causes over one million deaths every year worldwide. However, prevention and treatment methods for this serious disease are limited. The identification of new chemicals related to lung cancer may aid in disease prevention and the design of more effective treatments. This study employed a weighted network, constructed using chemical-chemical interaction information, to identify new chemicals related to two types of lung cancer: non-small lung cancer and small-cell lung cancer. Then, a randomization test as well as chemical-chemical interaction and chemical structure information were utilized to make further selections. A final analysis of these new chemicals in the context of the current literature indicates that several chemicals are strongly linked to lung cancer.

Anti-tumor effects of all-trans retinoic acid are enhanced by genistein

The effects of all-trans retinoic acid (ATRA) on cancer are complex. ATRA has anti-cancer effects as it promotes cancer cell differentiation. However, ATRA also up-regulates expression of vascular endothelial growth factor (VEGF) in cancer cells, which leads to angiogenesis and can, thus, facilitate cancer growth. Genistein, a crucial non-nutrient component in soybean, exhibits anti-cancer effects by inhibiting protein tyrosine kinase that is involved in up-regulation of VEGF. We hypothesized that genistein, applied simultaneously with ATRA, would counter its undesired angiogenic effects and, thus, enhance the anti-cancer effects of ATRA. The purpose of this study was to document potential synergistic effects of genistein and ATRA in A549 lung adenocarcinoma cells. We further explored the role of genistein on countering the ATRA-induced VEGF expression. We demonstrate that genistein enhances the ATRA-induced growth inhibition of A549 cells by promoting apoptosis. Further, the combined use of ATRA and genistein leads to cancer cell arrest in G0/G1 and G2/M cell cycle phases. Finally, expression of VEGF (both mRNA and protein) was diminished in A549 cells exposed to both ATRA and genistein. In conclusion, our results demonstrate that genistein effectively enhances anti-cancer effects of ATRA, particularly, by countering the ATRA-induced up-regulation of VEGF. Our study provides an experimental basis for combined use of ATRA and genistein in the treatment of lung cancer.

Bexarotene: a promising anticancer agent

Retinoids are biologically active derivatives of vitamin A, which play essential roles in embryonic or adult cell behavior modulating cell proliferation, differentiation and apoptosis. The biologic effects of retinoids are mediated by two distinct families of intracellular receptors: retinoid acid receptors (RARs)-α, -β and -γ and retinoid X receptors (RXR)-α, -β and -γ. Bexarotene is a selective RXR agonist, which exerts its effects in blocking cell cycle progression, inducing apoptosis and differentiation, preventing multidrug resistance, and inhibiting angiogenesis and metastasis, making it a promising chemopreventive agent against cancer.

Beyond doublet chemotherapy for advanced non-small-cell lung cancer: combination of targeted agents with first-line chemotherapy

The first-line treatment of advanced non-small-cell lung cancer (NSCLC) has evolved significantly over the past 5 years. As recently as 15 years ago, best supportive care (BSC) was considered an acceptable option for most patients with advanced or metastatic NSCLC, based on the concern that toxic effects of systemic chemotherapy overshadowed any potential benefits. The enhanced efficacy of platinum-based doublet chemotherapeutic regimens led to increases in overall patient survival relative to BSC. However, overall survival (OS) appeared to plateau, even with the introduction and refinement of these regimens. The addition of novel targeted agents targeting growth pathways to platinum-based regimens failed to overcome the 7.8- to 10.5-month survival barrier. After many phase III clinical trials, which involved tyrosine kinase inhibitors, matrix metalloproteinase inhibitors, protein kinase C inhibitors, and retinoids, this survival barrier had yet to be surmounted, although in some cases certain subgroups benefited, suggesting specific molecular correlations. Recently, inhibition of components of the angiogenesis pathway with the addition of bevacizumab to a platinum-based doublet led to statistically significant increases in OS, progression-free survival, and response rate relative to chemotherapy alone. This advance pushed the median survival of selected patients with advanced or metastatic NSCLC who met the eligibility criteria of the trial over the 12-month mark, thus offering patients and clinicians hope for more incremental advances in the future.

Inhibiting fatty acid synthase for chemoprevention of chemically induced lung tumors

PURPOSE

Fatty acid synthase (FAS) is overexpressed in lung cancer, and we have investigated the potential use of FAS inhibitors for chemoprevention of lung cancer.

EXPERIMENTAL DESIGN

Expression of FAS was evaluated in preinvasive human lung lesions (bronchial squamous dysplasia and atypical adenomatous hyperplasia) and in murine models of lung tumorigenesis [4-(methylnitrosamino)-I-(3-pyridyl)-1-butanone-induced and urethane-induced lung tumors in A/J mice]. Then, the ability of pharmacologic inhibitors of FAS to prevent development of the murine tumors was investigated. Finally, the effect of the FAS inhibitor treatment of levels of phosphorylated Akt in the murine tumors was evaluated by immunohistochemistry.

RESULTS

Immunohistochemical studies show that human bronchial dysplasia and atypical adenomatous hyperplasia express high levels of FAS compared with normal lung tissues, suggesting that FAS might be a target for intervention in lung carcinogenesis. FAS is also expressed at high levels in chemically induced murine lung tumors, and the numbers and sizes of those murine tumors are significantly reduced by treating carcinogen-exposed mice with pharmacologic inhibitors of FAS, C75 and C93. C93 treatment is associated with reduced levels of phosphorylated Akt in tumor tissues, suggesting that inhibition of this signal transduction pathway might be involved in the chemopreventative activity of this compound.

CONCLUSIONS

We conclude that increased levels of FAS are common in human preinvasive neoplasia of the lung. Based on studies in mouse models, it seems that inhibiting FAS is an effective strategy in preventing and retarding growth of lung tumors that have high expression of this enzyme.

Somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide in chemotherapy-pretreated patients with advanced lung adenocarcinoma and low performance status

BACKGROUND

We previously reported on an improvement in survival and quality of life in chemotherapy-naïve patients with advanced non-small-cell lung cancer and low performance status (PS) treated with a combination of biotherapeutical agents and cyclophosphamide. In this study, we assessed the survival, clinical status, and toxicity of this multidrug regimen in chemotherapy-pretreated patients with advanced lung adenocarcinoma and low PS.

METHODS

Patients with stage IIIB or IV lung adenocarcinoma, who had progressed after prior standard chemotherapy, and with an Eastern Cooperative Oncology Group PS > or = 2, received a daily combination of somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide.

RESULTS

Twenty-three (23) patients were enrolled. The median age was 59 years (range, 42-75). The PS was 2 and 3 in 73.9% and 26.1% of patients, respectively. The median overall survival (intent-to-treat analysis) was 95 days (range, 19-214). The side-effects were mild, mostly consisting of diarrhea, nausea and vomiting, and drowsiness of Grade 1-2. There was an improvement in both respiratory and general symptoms, which was more evident in patients surviving more than 95 days.

CONCLUSIONS

The combined regimen of somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide is well tolerated and can improve disease-related symptoms in heavily pretreated patients with late-stage lung adenocarcinoma and poor PS.

Somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide in advanced non-small-cell lung cancer patients with low performance status

BACKGROUND

The prognosis of low performance status (PS) patients with advanced non-small-cell-lung cancer (NSCLC) is dismal. In these patients, we have determined the survival, clinical benefits, and toxicity of a multidrug regimen, based on cyclophosphamide and biotherapeutical agents.

METHODS

Patients with a diagnosis of stage IIIB or stage IV NSCLC, no previous surgery or chemoradiotherapy, and an Eastern Cooperative Oncology Group (ECOG) PS equal to or greater than 2 received a daily combination of somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide.

RESULTS

Twenty-eight (28) patients were enrolled. The median age was 64 years (range, 35-74). The PS was 2 and 3 in 78.6% and 21.4% of patients, respectively. The median overall survival (intent-to-treat analysis) was 12.9 months (range, 1.5-33.5 months), The overall survival rates at 1 and 2 years were 51.2% and 21.1%, respectively. The side-effects were very mild, mostly consisting of diarrhoea, nausea/vomiting, and drowsiness of grade 1-2. Most patients experienced an improvement of both respiratory (cough and dyspnoea) and general (pain, fatigue, and insomnia) symptoms.

CONCLUSIONS

Low PS patients with advanced NSCLC may benefit from a combination of somatostatin, retinoids, melatonin, vitamin D, bromocriptine, and cyclophosphamide, in terms of survival and quality of life, with very low side-effects.

Synergistic antitumor activity of epidermal growth factor receptor tyrosine kinase inhibitor gefitinib and IFN-alpha in head and neck cancer cells in vitro and in vivo

PURPOSE

Epidermal growth factor receptor (EGFR) overexpression has been implicated in the development of head and neck squamous cell carcinomas (HNSCC) and represents a potential therapeutic target for this disease. We have reported previously that growth inhibitory concentrations of IFN-alpha enhance the expression and activity of EGFR and that this effect could represent an escape mechanism to the growth inhibition and apoptotic cell death induced by IFN-alpha. In this study, we investigate whether the combination of IFN-alpha and gefitinib (Iressa, AstraZeneca Pharmaceuticals, Macclesfield, United Kingdom), a selective EGFR tyrosine kinase inhibitor, might have a cooperative antitumor effect on HNSCC-derived cell lines.

EXPERIMENTAL DESIGN

The interaction of IFN-alpha and gefitinib was evaluated in vitro on HNSCC-derived cell lines by median drug effect analysis calculating a combination index with CalcuSyn software and in vivo by using HNSCC xenografts in nude mice. The mechanism of gefitinib and IFN-alpha interactions was also studied by analysis of cell cycle kinetics, apoptosis assays, and Western blotting of EGFR signal transduction components.

RESULTS

Simultaneous exposure to gefitinib and IFN-alpha produced synergistic antiproliferative and proapoptotic effects compared with single drug treatment. Furthermore, daily treatment of gefitinib (50 mg/kg p.o.) in combination with an IFN-alpha regimen (50,000 units s.c. three times weekly) induced tumor growth delay and increased survival rate on established HNSCC xenografts in nude mice. Moreover, the concomitant treatment with gefitinib suppressed the stimulation of extracellular signal-regulated kinase phosphorylation/activity induced by IFN-alpha both in vitro and in vivo.

CONCLUSION

The observed cooperative antitumor effects could be, at least in part, explained by the inhibition exerted by gefitinib of an IFN-alpha-induced EGF-dependent survival pathway, which involves extracellular signal-regulated kinase activation. These results provide a rationale for the clinical evaluation of gefitinib in combination with IFN-alpha in HNSCC.

Emerging role of rexinoids in non-small cell lung cancer: focus on bexarotene

Although the introduction of third-generation antineoplastic agents in the treatment of non-small cell lung cancer has led to modest improvements in overall patient survival, lung cancer continues to be the leading cause of cancer-related death worldwide, and improved therapies are needed. Retinoids play a critical role in the regulation of cell division, growth, differentiation, and proliferation, and they represent an exciting new avenue for targeted therapy. Several synthetic retinoids that bind to retinoic acid receptors are currently being investigated in a variety of tumor types. However, many of these agents have been associated with cheilitis, skin reactions, severe headache, and hypertriglyceridemia. Synthetic agents that bind specifically to retinoid X receptors are called rexinoids. Bexarotene (Targretin; Ligand Pharmaceuticals; San Diego, CA; http://www.ligand.com) is a novel, multitargeted synthetic rexinoid that is currently being investigated in the treatment of non-small cell lung cancer. Phase I and II studies have demonstrated that bexarotene is safe and well tolerated in this patient population either alone or in combination with chemotherapeutic agents. Patients treated with bexarotene experience manageable adverse events at reduced levels compared with retinoic acid receptor-specific retinoids. Bexarotene in combination with chemotherapeutic agents has demonstrated an encouraging median survival for patients with advanced non-small cell lung cancer compared with historical results with combination chemotherapy alone. Two phase III trials are currently under way to fully characterize the role of bexarotene in the treatment of this disease. The purpose of this review is to explore the rationale for rexinoids in the treatment of malignancies and to discuss the clinical profile of bexarotene in the treatment of non-small cell lung cancer.

Candidate gene approach for pharmacogenetic studies

Genetic diversity in the form of single nucleotide DNA polymorphisms (SNPs) contributes to variable disease susceptibility and drug response. The candidate gene approach has been widely used to identify the genetic basis for pharmacogenetic traits and becomes increasingly more powerful with the recent advances in genomic technologies. High-throughput sequencing and SNP genotyping technologies allow the study of thousands of candidate genes and the identification of those involved in drug efficacy and toxicity. Expression-based genomic technologies such as DNA microarrays and proteomics also facilitate the understanding of important biological and pharmacological pathways, thus identifying more candidate genes for SNP studies. Candidate gene-based pharmacogenetic studies will lead to improved drug development, improved clinical trial design and therapeutics tailored to individual genotypes.

Combinatorial chemoprevention of intestinal neoplasia

A combination of two drugs afforded remarkable protection from intestinal neoplasia in APC(Min/+) mice, a murine model of human familial adenomatous polyposis (FAP). One of the drugs was sulindac, a prototypical non-steroidal anti-inflammatory drug with established chemopreventative activity. The second drug was EKI-569, a newly developed, irreversible inhibitor of the epidermal growth factor receptor kinase. Although 100% of the untreated APC(Min/+) mice developed approximately 20 polyps, nearly half the mice treated with these two agents developed no polyps at all. These results suggest a powerful strategy for the chemoprevention of human colonic neoplasia.