Polyamine Biosynthetic Pathway as a Drug Target for Osteosarcoma Therapy

Abstract

Osteosarcoma (OS) is the most common bone tumor in children. Polyamines (PAs) are ubiquitous cations involved in many cell processes including tumor development, invasion and metastasis. In other pediatric cancer models, inhibition of the PA biosynthesis pathway with ornithine decarboxylase (ODC) inhibitor alpha-difluoromethylornithine (DFMO) results in decreased cell proliferation and differentiation. In OS, the PA pathway has not been evaluated. DFMO is an attractive, orally administered drug, is well tolerated, can be given for prolonged periods, and is already used in pediatric patients. Three OS cell lines were used to study the cellular effects of PA inhibition with DFMO: MG-63, U-2 OS and Saos-2. Effects on proliferation were analyzed by cell count, flow cytometry-based cell cycle analysis and RealTime-Glo™ MT Cell Viability assays. Intracellular PA levels were measured with high-performance liquid chromatography (HPLC). Western blot analysis was used to evaluate cell differentiation. DFMO exposure resulted in significantly decreased cell proliferation in all cell lines. After treatment, intracellular spermidine levels were drastically decreased. Cell cycle arrest at G2/M was observed in U-2 OS and Saos-2. Cell differentiation was most prominent in MG-63 and U-2 OS as determined by increases in the terminal differentiation markers osteopontin and collagen 1a1. Cell proliferation continued to be suppressed for several days after removal of DFMO. Based on our findings, DFMO is a promising new adjunct to current osteosarcoma therapy in patients at high risk of relapse, such as those with poor necrosis at resection or those with metastatic or recurrent osteosarcoma. It is a well-tolerated oral drug that is currently in phase II clinical trials in pediatric neuroblastoma patients as a maintenance therapy. The same type of regimen may also improve outcomes in osteosarcoma patients in whom there have been essentially no medical advances in the last 30 years.

Inhibition of the polyamine synthesis enzyme ornithine decarboxylase sensitizes triple-negative breast cancer cells to cytotoxic chemotherapy

“…Polyamines promote cell cycle progression (33), and depletion of ODC or polyamines induces cell cycle arrest at the G2/M phase (34)(35)(36), where cells are more sensitive to DNA damage induced by cisplatin and doxorubicin (37-39). Since we observed a decrease in polyamines and ODC activity following chemotherapy treatment, we reasoned that targeting ODC to further decrease polyamines could increase tumor cell killing.…”

The outcome of arginase activity inhibition in BALB/c mice hosting Leishmania tropica

“…Controlling the metabolic pathways that play a crucial role in the parasite life, such as polyamine biosynthetic pathway, could act as an alternative strategy for biological therapy . Here, we used nor‐NOHA to treat L. tropica ‐infected BALB/c mice to evaluate the in vivo effect of ARG activity on parasite infectivity.…”

“…Controlling the metabolic pathways that play a crucial role in the parasite life, such as polyamine biosynthetic pathway, could act as an alternative strategy for biological therapy. 8 Here, we used nor- and second, L. tropica creates a minor CL phenotype with a chronic course in BALB/c mice. 18,21 Following the prevention of ARG activity, the parasite burden declined in the dLNs of mice in nor-NOHA-Ltrop group in comparison with PBS-Ltrop group despite the fact that footpad size was not remarkably different between two groups.…”

“…One of the vital biological pathways of the live cells is the urea cycle which metabolizes L‐arginine to urea and ornithine and generates the polyamines as the final products . ARG therefore acts as the main target for biological drugs, since arginine metabolism inhibition stops polyamine storage leading to cell death . Arginine is the common substrate for two essential enzymes, arginase (ARG) and nitric oxide synthetase (NOS) isoforms.…”

“…metabolism inhibition stops polyamine storage leading to cell death. [7][8][9] Arginine is the common substrate for two essential enzymes, arginase (ARG) and nitric oxide synthetase (NOS) isoforms. Thus, any change in the quantity of arginine directly affects the activity of both enzymes.…”