Inhibition of tumor growth by biodegradable microspheres containing all-trans-retinoic acid in a human head-and-neck cancer xenograft

Opposite Effects of CRABP1 and CRABP2 Homologs on Proliferation of Breast Cancer Cells and Their Sensitivity to Retinoic Acid

Resistance of tumor cells to retinoic acid (RA), a promising therapeutic agent, is the major factor limiting the use of RA in clinical practice. The mechanisms of resistance to RA are still poorly understood. Cellular Retinoic Acid Binding Proteins, CRABP1 and CRABP2, are essential mediators of RA signaling, but role of the two CRABP homologs in regulating cellular sensitivity to RA has not been well studied. In addition, the effects of CRABP1 and CRABP2 on cell proliferation have not been compared. Here, using a broad panel of breast cancer cell lines with different levels of RA sensitivity/resistance, we show for the first time that in the RA-sensitive cells, CRABP1 expression is restricted by methylation, and protein levels are highly variable. In the moderately-RA-resistant cell lines, high level of CRABP1 is observed both at the mRNA and protein levels, unchanged by inhibition of DNA methylation. The cell lines with maximum resistance to RA are characterized by complete repression of CRABP1 expression realized at transcriptional and posttranscriptional levels, and exogenous expression of each of the CRABP homologs has no effect on the studied characteristics. CRABP1 and CRABP2 proteins have opposing effects on proliferation and sensitivity to RA. In particular, CRABP1 stimulates and CRABP2 reduces proliferation and resistance to RA in the initially RA-sensitive cells, while in the more resistant cells the role of each homolog in both of these parameters is reversed. Overall, we have shown for the first time that CRABP proteins exert different effects on the growth and sensitivity to RA of breast cancer cells (stimulation, suppression, or no effect) depending on the baseline level of RA-sensitivity, with the effects of CRABP1 and CRABP2 homologs on the studied properties always being opposite.

Sphingosine kinases are involved in the regulation of all-trans retinoic acid sensitivity of K562 chronic myeloid leukemia cells

The efficacy of all-trans retinoic acid (ATRA) for the treatment of chronic myeloid leukemia (CML) has been reported to be limited both as single-drug treatment or in combination with other drugs. Our previous study demonstrated that sphingosine 1-phosphate attenuated the effects of ATRA on human colon cancer cells by blocking the expression of retinoic acid receptor β. The aim of the present study was to investigate whether the ATRA-dependent proliferation inhibition of K562 cells was regulated by sphingosine kinases (SphKs). The results of cell proliferation assay and reverse transcription-PCR demonstrated that ATRA may exert synergistic effects with the SphK1 inhibitor SKI 5C or the pan-SphK inhibitor SKI II to inhibit the proliferation of K562 cells and upregulate the expression levels of the ATRA-inducible enzyme cytochrome P450 26A1 (CYP26A1). Knocking down the expression of SphK1 or SphK2 in K562 cells by small interfering RNA enhanced the inhibitory effects of ATRA and induced the expression of CYP26A1. Crude asterosaponins, which abrogated the expression of SphK2, also enhanced the effects of ATRA on K562 cells. In conclusion, the results of the present study demonstrated that SphKs may be involved in the regulation of the sensitivity of CML cells to ATRA.

Current Trends in ATRA Delivery for Cancer Therapy

All-Trans Retinoic Acid (ATRA) is the most active metabolite of vitamin A. It is critically involved in the regulation of multiple processes, such as cell differentiation and apoptosis, by activating specific genomic pathways or by influencing key signaling proteins. Furthermore, mounting evidence highlights the anti-tumor activity of this compound. Notably, oral administration of ATRA is the first choice treatment in Acute Promyelocytic Leukemia (APL) in adults and NeuroBlastoma (NB) in children. Regrettably, the promising results obtained for these diseases have not been translated yet into the clinics for solid tumors. This is mainly due to ATRA-resistance developed by cancer cells and to ineffective delivery and targeting. This up-to-date review deals with recent studies on different ATRA-loaded Drug Delivery Systems (DDSs) development and application on several tumor models. Moreover, patents, pre-clinical, and clinical studies are also reviewed. To sum up, the main aim of this in-depth review is to provide a detailed overview of the several attempts which have been made in the recent years to ameliorate ATRA delivery and targeting in cancer.

Progress in Drug and Formulation Development for the Chemoprevention of Oral Squamous Cell Carcinoma: A Review

BACKGROUND

Cancer is a life-threatening global problem with high incidence rates. Prioritizing the prevention of cancer, chemopreventive agents have drawn much attention from the researchers.

OBJECTIVE

This review focuses on the discussion of the progress in the development of chemopreventive agents and formulations related to the prevention of oral cancer.

METHODS

In this perspective, an extensive literature survey was carried out to understand the mechanism, control and chemoprevention of oral cancer. Different patented agents and formulations have also exhibited cancer preventive efficacy in experimental studies. This review summarizes the etiology of oral cancer and developments in prevention strategies.

RESULTS

The growth of oral cancer is a multistep activity necessitating the accumulation of genetic as well as epigenetic alterations in key regulatory genes. Many risk factors are associated with oral cancer. Genomic technique for sequencing all tumor specimens has been made available to help detect mutations. The recent development of molecular pathway and genetic tools has made the process of diagnosis easier, better forecast and efficient therapeutic management. Different chemical agents have been studied for their efficacy to prevent oral cancer and some of them have shown promising results.

CONCLUSION

Use of chemopreventive agents, either synthetic or natural origin, to prevent carcinogenesis is a worthy concept in the management of cancers. Preventive measures are helpful in controlling the occurrence or severity of the disease. The demonstrated results of preventive agents have opened an arena for the development of promising chemopreventive agents in the management of oral squamous cell carcinoma.

Triple primary cancer of the head and neck, skin and prostate: A case report and literature review

Second primary cancer (SPC) is an important prognostic factor for patients with head and neck cancer (HNC); therefore, the association between the prognosis and development of SPC has been well-reported. The use of 2-[18F]-fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET) is valuable to examine cancer stage, evaluate treatment responses and investigate suspected relapses or metastases. In the present study, the case of a male patient who was diagnosed with three primary cancer types, including well to moderately differentiated squamous cell carcinoma (SCC) of the mandible, axillary cutaneous poorly differentiated SCC and prostate adenocarcinoma, was described. Among these, mandible cancer was the first diagnosed when the patient was 70 years of age. Synchronous skin and prostate cancer (PRC) types then developed 3 years later. To the best of our knowledge, this is the first report of the aforementioned combination of cancer types. Postoperative FDG-PET was not performed as no lesions of recurrence or metastases of mandible cancer were found. Three years later, the PRC was asymptomatic and was incidentally detected by FDG-PET performed for a preoperative evaluation of skin cancer. It was indicated that FDG-PET could be utilized in patients with HNC due to there being no accurate FDG-PET protocol to detect SPC over a long-term follow-up.

Polymeric drug delivery systems for intraoral site-specific chemoprevention of oral cancer

Oral cancer is among the most prevalent cancers in the world. Moreover, it is one of the major health problems and causes of death in many regions of the world. The traditional treatment modalities include surgical removal, radiation therapy, systemic chemotherapy, or a combination of these methods. In recent decades, there has been significant interest in intraoral site-specific chemoprevention via local drug delivery using polymeric systems. Because of its easy accessibility and clear visibility, the oral mucosa is amenable for local drug delivery. A variety of polymeric systems-such as gels, tablets, films, patches, injectable systems (e.g., millicylindrical implants, microparticles, and in situ-forming depots), and nanosized carriers (e.g., polymeric nanoparticles, nanofibers, polymer-drug conjugates, polymeric micelles, nanoliposomes, nanoemulsions, and polymersomes)-have been developed and evaluated for the local delivery of natural and synthetic chemopreventive agents. The findings of in vitro, ex vivo, and in vivo studies and the positive outcome of clinical trials demonstrate that intraoral site-specific drug delivery is an attractive, highly effective and patient-friendly strategy for the management of oral cancer. Intraoral site-specific drug delivery provides unique therapeutic advantages when compared to systemic chemotherapy. Moreover, intraoral drug delivery systems are self-administrable and can be removed when needed, increasing patient compliance. This article covers important aspects and advances related to the design, development, and efficacy of polymeric systems for intraoral site-specific drug delivery. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1383-1413, 2018.

Fenretinide: a novel treatment for endometrial cancer

Resistance to progestin treatment is a major hurdle in the treatment of advanced and reoccurring endometrial cancer. Fenretinide is a synthetic retinoid that has been evaluated in clinical trials as a cancer therapeutic and chemo-preventive agent. Fenretinide has been established to be cytotoxic to many kinds of cancer cells. In the present study, we demonstrate that fenretinide decreased cell viability and induced apoptosis in Ishikawa cells, which are an endometrial cancer cell line, in dose dependent manner in-vitro. This effect was found to be independent of retinoic acid nuclear receptor signaling pathway. Further, we have shown that this induction of apoptosis by fenretinide may be caused by increased retinol uptake via STRA6. Silencing of STRA6 was shown to decrease apoptosis which was inhibited by knockdown of STRA6 expression in Ishikawa cells. Results of an in-vivo study demonstrated that intraperitoneal injections of fenretinide in endometrial cancer tumors (created using Ishikawa cells) in mice inhibited tumor growth effectively. Immunohistochemistry of mice tumors showed a decrease in Ki67 expression and an increase in cleaved caspase-3 staining after fenretinide treatment when compared to vehicle treated mice. Collectively, our results are the first to establish the efficacy of fenretinide as an antitumor agent for endometrial cancer both in-vitro and in-vivo, providing a valuable rationale for initiating more preclinical studies and clinical trials using fenretinide for the treatment of endometrial cancer.

Transcriptome profiling and genome-wide DNA binding define the differential role of fenretinide and all-trans RA in regulating the death and survival of human hepatocellular carcinoma Huh7 cells

Fenretinide is significantly more effective in inducing apoptosis in cancer cells than all-trans retinoic acid (ATRA). The current study uses a genome-wide approach to understand the differential role fenretinide and ATRA have in inducing apoptosis in Huh7 cells. Fenretinide and ATRA-induced gene expressions and DNA bindings were profiled using microarray and chromatin immunoprecipitation with anti-RXRα antibody. The data showed that fenretinide was not a strong transcription regulator. Fenretinide only changed the expressions of 1 093 genes, approximately three times less than the number of genes regulated by ATRA (2 811). Biological function annotation demonstrated that both fenretinide and ATRA participated in pathways that determine cell fate and metabolic processes. However, fenretinide specifically induced Fas/TNFα-mediated apoptosis by increasing the expression of pro-apoptotic genes i.e., DEDD2, CASP8, CASP4, and HSPA1A/B; whereas, ATRA induced the expression of BIRC3 and TNFAIP3, which inhibit apoptosis by interacting with TRAF2. In addition, fenretinide inhibited the expression of the genes involved in RAS/RAF/ERK-mediated survival pathway. In contrast, ATRA increased the expression of SOSC2, BRAF, MEK, and ERK genes. Most genes regulated by fenretinide and ATRA were bound by RXRα, suggesting a direct effect. This study revealed that by regulating fewer genes, the effects of fenretinide become more specific and thus has fewer side effects than ATRA. The data also suggested that fenretinide induces apoptosis via death receptor effector and by inhibiting the RAS/RAF/ERK pathway. It provides insight on how retinoid efficacy can be improved and how side effects in cancer therapy can be reduced.

Antioxidant potential of all-trans retinoic acid (ATRA) and enhanced activity of liposome encapsulated ATRA against inflammation and tumor-directed angiogenesis

The purpose of this study was to investigate whether all-trans retinoic acid (ATRA) has antioxidant property. The study was also focused on its inhibitory effect on the acute and chronic inflammation and tumor-associated capillary formation in terms of angiogenesis in C57BL/6 mice after incorporated in liposome composed of distearoylphosphatidylcholine (DSPC/cholesterol). ATRA possesses a number of important biologic activities including oncostatic, antioxidant and immunostimulatory actions. Our study was designed to evaluate the antioxidant activity of free ATRA by nitric oxide scavenging, superoxide radical scavenging, hydroxyl radical scavenging and lipid peroxide scavenging assays. The ATRA showed significant scavenging activities in all these antioxidant assays comparable to the standard antioxidant. We have also evaluated the activity of encapsulated ATRA against anti-inflammatory activity in C57BL/6 mice. The paw oedema inhibition was found in carrageenan model as 55.56% and 66.67% for free ATRA and encapsulated ATRA treatment respectively and for formaldehyde model it was found to be 60.87% and 69.57% respectively compared with saline treated control mice. Encapsulated ATRA inhibited the tumor-associated capillary formation in mice induced by highly metastatic B16F10 melanoma cells significantly than the free ATRA did. In this study the inhibition of tumor-directed capillary formation was found to be 56.25% and 62.50% for free ATRA and encapsulated ATRA treatment respectively. In conclusion, ATRA showed a significant antioxidant property in vitro. Free ATRA has anti-inflammatory activity as proved by us in animal model of acute and chronic inflammation and antiangiogenesis activity. Furthermore, its activity was boosted by encapsulation in liposome.

Inhibition of metastatic lung cancer in C57BL/6 mice by liposome encapsulated all trans retinoic acid (ATRA)

The purpose of this study was to investigate whether all trans retinoic acid (ATRA) incorporated in liposome composed of distearoylphosphatidylcholine (DSPC/cholesterol) could inhibit the metastatic lung cancer in mice more efficiently than free ATRA. Metastatic lung cancer model was developed by intravenous injection of B16F10 cells and it is also referred as melanoma model. In this present study, C57BL/6 mice were divided into several groups as per experimental design and the free ATRA and liposome encapsulated ATRA were given for 21 days at a dose of 0.60 mg/kg body weight/day after cell line implantation. After 21 days, mice were sacrificed at different time interval for ATRA level analysis in serum and lung tissue by HPLC method and the remaining mice were kept for anticancer study. The ATRA level increased significantly in serum and lung tissue in liposome encapsulated ATRA treated mice. In cancer bearing mice, tumor nodule formation decreased and life span increased after receiving liposome encapsulated ATRA treatment than free ATRA treated mice. This result implies that the liposome encapsulated ATRA has maintained more ATRA concentration in lung tissue and showed more inhibition on the lung tumor nodule formation. The results indicate a possible use of liposome encapsulated ATRA in prevention of lung metastasis.

Epigallocatechin gallate sensitizes CAL-27 human oral squamous cell carcinoma cells to the anti-metastatic effects of gefitinib (Iressa) via synergistic suppression of epidermal growth factor receptor and matrix metalloproteinase-2

Human head and neck squamous cell carcinoma (HNSCC) is a major cause of cancer-related death during the last decade due to its related metastasis and poor treatment outcomes. Gefitinib (Iressa), a tyrosine kinase inhibitor has been reported to reduce the metastatic abilities of oral cancer. Previous studies have shown that epigallocatechin gallate (EGCG), a green tea polyphenol, possesses cancer chemopreventive and anticancer activity. However, the mechanisms involved in the suppression of invasion and metastasis of human oral cancer cells following co-incubation with gefitinib and EGCG remain poorly understood. In the present study, we attempted to investigate the synergistic effects of a combined treatment of gefitinib and EGCG in CAL-27 cells in vitro and to elucidate the underlying molecular mechanisms associated with the supression of cell migration and invasion. In the present study, we found that the individual treatments or the combined treatment of gefitinib and EGCG synergistically inhibited the invasion and migration of CAL-27 cells using Transwell invasion and wound-healing scratch assays, respectively. Similarly, gefitinib in combination with EGCG synergistically attenuated enzymatic activity and the protein expression of MMP-2 in CAL-27 cells. Furthermore, individual or combined treatment with EGCG and gefitinib suppressed the protein expression of p-EGFR and the phosphorylated protein levels of ERK, JNK, p38 and AKT and displayed inhibitory effects on metastatic ability of CAL-27 cells. Combined effects of EGCG and gefitinib-altered anti-metastatic actions for related gene expression were observed using DNA microarray analysis. Importantly, EGCG sensitizes CAL-27 cells to gefitinib-suppressed phosphorylation of epidermal growth factor receptor (EGFR in vitro. Taken together, our results suggest that the synergistic suppression of the metastatic ability of CAL-27 cells after EGCG and gefitinib individual or combined treatment are mediated through mitogen-activated protein kinase (MAPK) signaling. Our novel findings provide potential insights into the mechanism involved with synergistic responses of gefitinib and EGCG against the progression of oral cancer.

Topical polyethylene glycol as a novel chemopreventive agent for oral cancer via targeting of epidermal growth factor response

Head and neck squamous cell carcinoma (HNSCC) is a major cause of morbidity and mortality underscoring the need for safe and effective chemopreventive strategies. Targeting epidermal growth factor receptor (EGFR) is attractive in that it is an early critical event in HNSCC pathogenesis. However, current agents lack efficacy or have unacceptable toxicity. Several groups have demonstrated that the over-the-counter medication, polyethylene glycol (PEG) has remarkable chemopreventive efficacy against colon carcinogenesis. Importantly, we reported that this effect is mediated through EGFR internalization/degradation. In the current study, we investigated the chemopreventive efficacy of this agent against HNSCC, using both the well validated animal model 4-NQO (4-nitroquinoline 1-oxide) rat model and cell culture with the human HNSCC cell line SCC-25. We demonstrated that daily topical application of 10% PEG-8000 in the oral cavity (tongue and cavity wall) post 4NQO initiation resulted in a significant reduction in tumor burden (both, tumor size and tumors/tumor bearing rat) without any evidence of toxicity. Immunohistochemical studies depicted decreased proliferation (number of Ki67-positive cells) and reduced expression of EGFR and its downstream effectors cyclin D1 in the tongue mucosa of 4NQO-rats treated with PEG. We showed that EGFR was also markedly downregulated in SCC-25 cells by PEG-8000 with a concomitant induction of G1-S phase cell-cycle arrest, which was potentially mediated through upregulated p21(cip1/waf1). In conclusion, we demonstrate, for the first time, that PEG has promising efficacy and safety as a chemopreventive efficacy against oral carcinogenesis.

A clinically relevant bi-cellular murine mammary tumor model as a useful tool for evaluating the effect of retinoic acid signaling on tumor progression

BACKGROUND

The effect of retinoic acid (RA) on breast cancer progression is controversial. Our objective was to obtain information about breast cancer progression, taking advantage of the ER-negative murine mammary adenocarcinoma model LM38 (LM38-LP constituted by luminal (LEP) and myoepithelial-like cells (MEP), LM38-HP mainly composed of spindle-shaped epithelial cells, and LM38-D2 containing only large myoepithelial cells), and to validate the role of the retinoic acid receptors (RARs) in each cell-type compartment.

MATERIALS AND METHODS

We studied the expression and functionality of the RARs in LM38 cell lines. We analyzed cell growth and cell cycle distribution, apoptosis, the activity of proteases, motility properties, and expression of the molecules involved in these pathways. We also evaluated tumor growth and dissemination in vivo under retinoid treatment.

RESULTS

LM38 cell lines expressed most retinoic receptor isotypes that were functional. However, only the bi-cellular LM38-LP cells responded to retinoids by increasing RARβ2 and CRBP1 expression. The growth of LM38 cell sublines was inhibited by retinoids, first by inducing arrest in MEP cells, then apoptosis in LEP cells. Retinoids induced inhibitory effects on motility, invasiveness, and activity of proteolytic enzymes, mainly in the LM38-LP cell line. In in-vivo assays with the LM38-LP cell line, RA treatment impaired both primary tumor growth and lung metastases dissemination.

CONCLUSION

These in-vivo and in-vitro results show that to achieve maximum effects of RA on tumor progression both the LEP and MEP cell compartments have to be present, suggesting that the interaction between the LEP and MEP cells is crucial to full activation of the RARs.

Enhanced dissolution, stability and physicochemical characterization of ATRA/2-hydroxypropyl-β-cyclodextrin inclusion complex pellets prepared by fluid-bed coating technique

The aim of this work was to prepare stable all-trans-retinoic acid (ATRA)/2-hydroxypropyl-β-cyclodextrin (HPCD) inclusion complex pellets with industrial feasible technology, the fluid-bed coating technique, using PVP K30 simultaneously as binder and reprecipitation retarder. The coating process was fluent with high coating efficiency. In vitro dissolution of the inclusion complex pellets in 5% w/v Cremopher EL solution was dramatically enhanced with no reprecipitation observed, and significantly improved stability against humidity (92.5% and 75% RH) and illumination (4500 lx ± 500 lx) was achieved by HPCD inclusion. Differential scanning calorimetry and powder X-ray diffractometry confirmed the absence of crystallinity of ATRA. Fourier transform-infrared spectrometry revealed interaction between ATRA and HPCD adding evidence on inclusion of ATRA moieties into HPCD cavities. Solid-state (13)C NMR spectrometry indicated possible inclusion of ATRA through the polyene chain, which was the main reason for the enhanced photostability. It is concluded that the fluid-bed coating technique has the potential use in the industrial preparation of ATRA/HPCD inclusion complex pellets.

All trans retinoic acid and cancer

All-trans retinoic acid (ATRA) is an active metabolite of vitamin A under the family retinoid. Retinoids, through their cognate nuclear receptors, exert potent effects on cell growth, differentiation and apoptosis, and have significant promise for cancer therapy and chemoprevention. Differentiation therapy with ATRA has marked a major advance and become the first choice drug in the treatment of acute promyelocytic leukemia (APL). Conversions of 13-cis-retinoic acid and 9-cis-retinoic acid to all-trans-retinoic acid is very rapid. Currently, two distinct families of retinoid responsive nuclear receptors have been identified and characterized: retinoic acid receptors (RARs) and retinoid receptors (RXRs), each of which include three isoforms, α,β,and γ. ATRA is being increasingly included in anti-tumour therapeutical schemes for the treatment of various tumoral diseases such as Kaposi's sarcoma, head and neck squamous cell carcinoma, ovarian carcinoma, bladder cancer, neuroblastoma and has shown antiangiogenic effects in several systems, inhibiting proliferation in vascular smooth muscle cells (VSMCs) and anti-inflammatory in rheumatoid arthritis. This review helps to understand in details about the ATRA and its role on cancer and it is predicted that modulating the activity of ATRA will soon provide novel prevention and treatment approaches for the cancer patients.

[Precision TACE in therapy of primary malignant tumors of liver/hepatocellular carcinoma (HCC)]

AIM

Hepatocellular carcinoma is one of the most frequent malignant tumors in general and most common liver malignancy. Aim of this study was to determine the therapeutic effect of chemoembolization with microspheres charged with doxorubicin in HHC patients.

MATERIAL AND METHODS

During for period of four-year (November 2005- November 2009) at Institute of radiology CC Ni transarterial chemoembolization procedures (precision TACE) was performed on 27 patients. There were 17 male and 10 female patients with average age of 62 years. Total number of 64 TACE interventions were done in total, minimally one, maximally 6 per patient. HCC was pathophysiologically verified in all patients included in this study. After selective catheterization of tumor feeding artery, followed by application of microspheres a follow-up study with evaluation of therapeutic effects was conducted.

RESULTS

Patients were enrolled in the study and followed four years in total. The therapy effects were estimated according to RECIST criteria.

CONCLUSION

Precision TACE represents effective and controlled method for application of chemotherapeutic agencies with reduced systemic toxicity. Our preliminary results show increased therapeutic efficacy, diminished mortality and subsequently prolonged survival rate and improved quality of life in patients with HCC.

Anti-tumor Effect of All-Trans Retinoic Acid Loaded Polymeric Micelles in Solid Tumor Bearing Mice

PURPOSE

All-trans retinoic acid (ATRA) polymeric micelles were developed for parenteral administration. The distribution characteristics and antitumor activities of ATRA polymeric micelles were evaluated after intravenous administration to mice bearing CT26 solid tumors.

METHODS

ATRA incorporated in poly(ethylene glycol)-poly(benzyl aspartate) block copolymer was prepared by the evaporation method. The levels of [3H]ATRA in blood and tissue including tumor were determined by measuring the radioactivity after injection into mice. The tumor volume and the survival of the mice were determined to assess the anticancer activity.

RESULTS

The delivery of ATRA by polymeric micelles prolonged the blood circulation and enhanced the accumulation of ATRA in the tumor tissue compared with the administration of free ATRA. Tumor growth was significantly delayed and the survival time of mice was prolonged following the treatment by ATRA polymeric micelles demonstrating the improved anticancer activity of ATRA.

CONCLUSION

Polymeric micelles are a promising and effective carrier of ATRA in order to enhance tumor delivery and they have a promising potential application in the treatment of solid tumors.

Inhibition of pulmonary metastasis in mice by all-trans retinoic acid incorporated in cationic liposomes

The purpose of this study was to investigate whether all-trans retinoic acid (ATRA), an active metabolite of retinal, incorporated in cationic liposomes composed of 1,2 dioleoyl-3-trimethylammonium propane (DOTAP)/cholesterol could inhibit established metastatic lung tumors by delivery to the pulmonary tumor site after intravenous injection. After intravenous injection in mice, the highest lung accumulation of [(3)H]ATRA was observed by the DOTAP/cholesterol liposomes formulation, while other formulations including [(3)H]ATRA dissolved in serum or [(3)H]ATRA incorporated in distearoyl-l-phosphatidylcholine (DSPC)/cholesterol liposomes produced little accumulation in the lung. In mice used as a model of lung cancer metastasis, ATRA incorporated in DOTAP/cholesterol liposomes, injected intravenously, reduced the number of tumor nodules compared with free ATRA or ATRA incorporated in DSPC/cholesterol liposomes. These results suggest that ATRA incorporated in cationic liposomes would be an effective strategy for differentiation therapy of lung cancer metastasis.

Primary tumour genetic alterations and intra-tumoral heterogeneity are maintained in xenografts of human colon cancers showing chromosome instability

Evaluation of the role of clonal heterogeneity in colon tumour sensitivity/resistance to drugs and/or in conferring metastatic potential requires an adequate experimental model in which the tumour cells maintain the initial genetic alterations and intra-tumoral heterogeneity through maintenance of the genetic clones present in the initial tumour. Therefore, we xenografted subcutaneously into nude mice seven human colonic tumours (from stages B1 to D) that showed chromosome instability and transplanted them sequentially for up to 14 passages. Maintenance after xenografting of the genetic alterations present in the initial tumours was scored by allelotype studies targeting 45 loci localized on 18 chromosomes. We show that xenografting does not alter the genetic or the histological profiles of the tumours even after 14 passages. Screening of the entire genome of one tumour by comparative genome hybridization also showed overall stability of the alterations between the initial and the xenografted tumour. In addition, intra-tumoral heterogeneity was maintained over time, suggesting that no clonal selection occurred in the nude mice. The observation that some loci showed partial allelic imbalance in the initial tumour but loss of heterozygosity after the first passage in nude mice when all the normal cells were lost may allow identification of interesting genetic defects that could be involved in tumour expansion. Thus, sequential xenografts of colon tumours will provide a powerful model for further study of tumour clonality and for the identification of genetic profiles responsible for differential resistance to therapeutic treatments. Our data also suggest that tumour expansion can result from alterations in several distinct genetic pathways.

Animal models for the study of squamous cell carcinoma of the upper aerodigestive tract: a historical perspective with review of their utility and limitations. Part A. Chemically-induced de novo cancer, syngeneic animal models of HNSCC, animal models of transplanted xenogeneic human tumors

Understanding the complex histological, genetic and molecular changes that lead to malignant transformation of squamous epithelia of the head and neck will likely guide the development of methods for improved diagnosis, monitoring and treatment of head and neck squamous cell carcinoma (HNSCC). The development and use of animal models that closely mimic the histopathology and molecular pathogenesis of HNSCC in humans would greatly expand the research possibilities and provide a means of testing potential therapeutic agents. However, many available animal models of HNSCC fall short of this objective. In order for investigators to select the appropriate model to answer scientific questions, it is important to understand the benefits and limitations of available animal models for the study of HNSCC. The purpose of this work is to give an overview of the most pertinent animal models of HNSCC, and to discuss future directions of research in this field.

Induction of apoptosis in A549 human lung cancer cells by all-trans retinoic acid incorporated in DOTAP/cholesterol liposomes

All-trans retinoic acid (ATRA) has been shown to exert anti-cancer activities in a number of types of cancer cells. However, it has been reported that many NSCLC exhibited resistance to ATRA treatment. In the present study, we hypothesized that intracellular delivery of ATRA would overcome the ATRA resistance in A549 cells. Here, we investigated the induction of apoptosis by ATRA incorporated in cationic liposomes composed of DOTAP/cholesterol in A549 human lung cancer cells, which are insensitive (resistant) to the growth inhibitory effects of ATRA. The zeta potentials of DOTAP/cholesterol liposomes and DSPC/cholesterol liposomes were about +50 and -3 mV. In A549 cells, [(3)H]ATRA incorporated in DOTAP liposomes showed increased cellular association compared with [(3)H]ATRA or [(3)H]ATRA incorporated in DSPC/cholesterol liposomes. ATRA incorporated in DOTAP/cholesterol liposomes showed much higher cytotoxic effects and apoptosis-inducing activity compared with ATRA or ATRA incorporated in DSPC/cholesterol liposomes. The enhanced expression of TIG3 mRNA tumor suppressor gene by ATRA incorporation into DOTAP/cholesterol liposomes might partly explain the mechanism of enhanced cytotoxicity and/or apoptosis. These observations provide valuable information to help in the design of differentiation therapy by ATRA in non-small cell lung carcinoma.

Biodistribution characteristics of all-trans retinoic acid incorporated in liposomes and polymeric micelles following intravenous administration

The aim of this study was to investigate the biodistribution characteristics of all-trans retinoic acid (ATRA) incorporated in liposomes and polymeric micelles following intravenous administration. [3H] ATRA were incorporated in distearoylphosphatidylcholine (DSPC)/cholesterol (6:4) liposomes. Two types of block copolymers, poly (ethylene glycol)-b-poly-(aspartic acid) derivatives with benzyl (Bz-75) groups, were synthesized to prepare the polymeric micelles for [(3)H]ATRA incorporation. ATRA were dissolved in mouse serum to analyze their inherent distribution. After intravenous administration, the blood concentration of [3H] ATRA in liposomes and polymeric micelles (Bz-75) was higher than that of inherent [3H]ATRA, suggesting that liposomes and polymeric micelles (Bz-75) control the distribution of ATRA. Pharmacokinetic analysis demonstrated that [3H]ATRA incorporated in polymeric micelles (Bz-75) exhibit the largest AUC(blood) and lowest hepatic clearance of ATRA, suggesting that polymeric micelles (Bz-75) are an effective ATRA carrier system for acute promyelocytic leukemia (APL) therapy. These results have potential implications for the design of ATRA carriers for APL patients.

Modified polyvinylalcohol for encapsulation of all-trans-retinoic acid in polymeric micelles

All-trans-retinoic acid (ATRA) is now included in many antitumor therapeutic schemes for the treatment of acute promyelocytic leukaemia, Kaposi's sarcoma, head and neck squamous cell carcinoma, ovarian carcinoma, bladder cancer and neuroblastoma. Unfortunately its poor aqueous solubility hampers its parenteral formulation. To date, there is no parenteral formulation of ATRA commercially available and oral administration of ATRA is associated with progressively diminishing ATRA levels in plasma, which is related to induction of retinoic acid-binding protein and increased drug catabolism by cytochrome P-450-mediated reaction. An ATRA formulation, obtained by complexation of the drug into polymeric micelles, might be suitable for parenteral administration overcoming these unwanted effects. To this purpose we prepared an amphiphilic polymer by polyvinylalcohol (PVA) substitution with oleyl amine at 1.5% substitution degree (mol substituent per 100 mol hydroxyvinylmonomer) and evaluated its functional properties with regard to ATRA complexation. The substituted polymer displayed ability to interact with ATRA both in aqueous solution and in the solid state following spray-drying of drug-polymer hydro-alcoholic solutions. The spray-dried complexes rapidly dissolved in water providing high levels of ATRA solubilization as a function of the drug-polymer weight ratio. The complexes characterized by 1:5 drug-polymer weight ratio provided higher levels of ATRA solubilization than 1:3 and 1:10 drug-polymer weight ratios respectively. Pre-formed polymeric micelles in water equilibrated in the presence of excess solid ATRA provided the lowest levels of solubilization. The drug release from the complexes was very slow in PBS, indicating their suitability in antitumor drug targeting where a fundamental requirement is stability towards drug release for at least 24 h, corresponding to the average circulation time period of macromolecular carriers. The cytotoxicity studies against neuroblastoma cell lines outlined increased cytotoxicity of complexed ATRA with respect to free ATRA, likely due to the increased bioavailability of the hydrophobic drug from the complex. We conclude that ATRA entrapped into self-assembling polymer micelles may be a useful parenteral ATRA formulation overcoming the unwanted pharmacological mechanism that lead to acquired retinoid resistance.

Chemoprevention of 4-NQO-induced oral carcinogenesis by co-administration of all-trans retinoic acid loaded microspheres and celecoxib

All-trans retinoic acid (atRA) is one of the most potential chemopreventive agents for head and neck squamous cell carcinoma (HNSCC). However, the induced metabolism of atRA by cytochrome P450s in the liver limits its clinical applications. To overcome such limitation, we had developed atRA-loaded microspheres designed to release atRA for a long period. Unfortunately, the atRA-loaded microspheres severely induced inflammatory responses: that is, atRA released from the microspheres significantly induced the proliferation of fibroblasts and collagen deposition, thereby causing a permeability barrier for drugs from entering the blood stream. In the present study, the effects of celecoxib as an anti-inflammatory drug are investigated when it is concurrently used with atRA-loaded microspheres to treat 4-NQO-induced oral carcinogenesis. We investigated if it might influence the plasma concentration of atRA and its metabolism by preventing the fibroblast proliferation and collagen deposition, reduce the toxicity level of atRA, and improve the chemopreventive efficacy of atRA-loaded microspheres. The concurrently administered celecoxib prevented inflammatory responses and suppressed the number of fibroblasts and collagen deposition in the fibrous capsules for 14 days. The atRA concentration in plasma was also increased and the metabolism of atRA was significantly decreased within 2 weeks. In the 4-NQO-induced oral carcinogenesis study, the incidence of invasive SCC was above 44% when F344 rats were treated with atRA-loaded microspheres. However, the treatment using atRA-loaded microspheres and celecoxib concurrently could reduce the incidence of invasive SCC up to 28%, and three of 25 rats were found to have no tongue lesions. In conclusion, the concurrent use of celecoxib could maintain the atRA concentration in plasma at a higher level while reducing its metabolism by preventing inflammatory responses, thereby improving their chemopreventive effects against 4-NQO-induced oral carcinogenesis.

Altered chemical and biological activities of all-trans retinoic acid incorporated in solid lipid nanoparticle powders

The principal aim of this study was to investigate whether the solid lipid nanoparticle (SLN) powder formulation of all-trans retinoic acid (ATRA) can favorably alter the chemical stability and biological activities of ATRA. SLN powder formulation of ATRA was obtained by freeze-drying of SLN dispersions. The chemical stability of ATRA was determined by HPLC analysis. The anticancer efficacy of ATRA was determined by evaluating antiproliferative effects of ATRA on cancer cell lines. Hemolytic potential of ATRA was spectrophotometrically determined after incubation with red blood cells (RBCs) in vitro. ATRA could be efficiently incorporated in SLN powder without impairing the physical stability of lipid nanoparticles. After 3 months of storage, >90% ATRA remained intact in SLN powder, indicating that the chemical stability of ATRA was substantially improved by incorporation in SLN powder. The antiproliferative effects of SLN powder formulation of ATRA on a wide range of cancer cell lines were not significantly different from that of free ATRA. Furthermore, the incorporation of ATRA in SLN powder significantly reduced the hemolytic potential of ATRA. Taken together, the molecular characteristics that currently appear to limit the clinical efficacy of ATRA were greatly improved by preparing SLN powder formulation. SLN powder formulation of ATRA may have a potential in enhancing the efficacy of ATRA in cancer chemoprevention and therapeutics.