Synergistic Effects of Acyclic Retinoid and OSI-461 on Growth Inhibition and Gene Expression in Human Hepatoma Cells

Abstract

Hepatoma is one of the most frequently occurring cancers worldwide. However, effective chemotherapeutic agents for this disease have not been developed. Acyclic retinoid, a novel synthetic retinoid, can reduce the incidence of postsurgical recurrence of hepatoma and improve the survival rate. OSI-461, a potent derivative of exisulind, can increase intracellular levels of cyclic GMP, which leads to activation of protein kinase G and induction of apoptosis in cancer cells. In the present study, we examined the combined effects of acyclic retinoid plus OSI-461 in the HepG2 human hepatoma cell line. We found that the combination of as little as 1.0 mol/L acyclic retinoid and 0.01 mol/L OSI-461 exerted synergistic inhibition of the growth of HepG2 cells. Combined treatment with low concentrations of these two agents also acted synergistically to induce apoptosis in HepG2 cells through induction of Bax and Apaf-1, reduction of Bcl-2 and Bcl-x L , and activation of caspase-3, -8, and -9. OSI-461 enhanced the G 0 -G 1 arrest caused by acyclic retinoid, and the combination of these agents caused a synergistic decrease in the levels of expression of cyclin D1 protein and mRNA, inhibited cyclin D1 promoter activity, decreased the level of hyperphosphorylated forms of the Rb protein, induced increased cellular levels of the p21 CIP1 protein and mRNA, and stimulated p21 CIP1 promoter activity. Moreover, OSI-461 enhanced the ability of acyclic retinoid to induce increased cellular levels of retinoic acid receptor ␤ and to stimulate retinoic acid response element-chloramphenicol acetyltransferase activity. A hypothetical model involving concerted effects on p21 CIP1 and retinoic acid receptor ␤ expression is proposed to explain these synergistic effects. Our results suggest that the combination of acyclic retinoid plus OSI-461 might be an effective regimen for the chemoprevention and chemotherapy of human hepatoma and possibly other malignancies.

Acyclic Retinoid Inhibits Diethylnitrosamine-Induced Liver Tumorigenesis in Obese and Diabetic C57BLKS/J- +Leprdb/+Leprdb Mice

“…ACR suppresses the growth of HCC cells by inhibiting RXRa phosphorylation and restoring its original function as a master regulator of nuclear receptors (15,(22)(23)(24). Therefore, the expression levels of the RARb, p21 CIP1 , cyclin D1, c-Fos, and c-Jun genes, which are ACR targets (12)(13)(14)(15)28), were notably regulated by treatment with this agent. Among these molecules, RARb seems to be the most important with respect to the induction of apoptosis (36).…”

“…Effects of ACR on the expression levels of RARb, p21 CIP1 , cyclin D1, c-Fos, and c-Jun mRNA in the livers of DEN-treated db/db mice ACR inhibits the growth of HCC cells by increasing the cellular levels of RARb and p21 CIP1 but decreasing the levels of cyclin D1, and these effects might be associated with the restoration of RXRa function (12)(13)(14)(15). It also suppresses the growth of cancer cells by inhibiting the activity of AP-1, which comprises the Jun and Fos oncoprotein families (28).…”

“…It inhibits experimental liver carcinogenesis and suppresses the growth of HCC-derived cells by inducing apoptosis and causing cell-cycle arrest in G 0 -G 1 (11)(12)(13)(14)(15). These effects of ACR are associated with its agonistic activity for distinct nuclear retinoid receptors-retinoid X receptors (RXR) and retinoic acid receptors (RAR), both of which have 3 subtypes (a, b, and g; 16)-and subsequent expression of the ACR target genes RARb and p21 CIP1 (12)(13)(14)(15). A clinical trial revealed that oral administration of ACR significantly reduced the incidence of posttherapeutic HCC recurrence and improved the survival rates of patients (17,18).…”

A dose-ranging study of the pharmacokinetics and pharmacodynamics of the selective apoptotic antineoplastic drug (SAAND), OSI-461, in patients with advanced cancer, in the fasted and fed state

“…OSI-461 exhibits a high affinity for PDE 2 and 5 compared to other drugs in this class thus resulting in greater selectivity for tumor cells [37]. Preclinical studies using OSI-461 have shown antitumor activity against a broad range of both solid and hematologic human cancer cell lines as both a single agent and in combination with other potential anticancer therapies [19,28,29,37,41]. This phase I and pharmacologic study was designed to evaluate the safety and toxicology profile of OSI-461 as well as determine the effect of food on the PKs of OSI-461 in patients with advanced malignancies.…”

“…In SW480 colon cancer cells lines at doses twice that of the IC50, OSI-461 was able to induce M phase cell cycle arrest independent of PKG activation resulting in depolymerization of microtubules, inhibition of spindle formation and induction of multinucleated cells [43]. In addition, modulation of key mechanisms involved in the malignant transformation has been seen in with single-agent use in LNCaP prostate cells and in combination with acyclic retinoid in HepG2 hepatoma cells [18,29].…”