Rapamycin Inhibits ALDH Activity, Resistance to Oxidative Stress, and Metastatic Potential in Murine Osteosarcoma Cells

Abstract

Osteosarcoma (OS) is the most common primary malignancy of bone. Mortality is determined by the presence of metastatic disease, but little is known regarding the biochemical events that drive metastases. Two murine OS cell lines, K7M2 and K12, are related but differ significantly in their metastatic potentials: K7M2 is highly metastatic whereas K12 displays much less metastatic potential. Using this experimental system, the mammalian target of rapamycin (mTOR) pathway has been implicated in OS metastasis. We also discovered that aldehyde dehydrogenase (ALDH, a stem cell marker) activity is higher in K7M2 cells than K12 cells. Rapamycin treatment reduces the expression and enzymatic activity of ALDH in K7M2 cells. ALDH inhibition renders these cells more susceptible to apoptotic death when exposed to oxidative stress. Furthermore, rapamycin treatment reduces bone morphogenetic protein-2 (BMP2) and vascular endothelial growth factor (VEGF) gene expression and inhibits K7M2 proliferation, migration, and invasion in vitro. Inhibition of ALDH with disulfiram correlated with decreased mTOR expression and activity. In conclusion, we provide evidence for interaction between mTOR activity, ALDH activity, and metastatic potential in murine OS cells. Our work suggests that mTOR and ALDH are therapeutic targets for the treatment and prevention of OS metastasis.

Chick Embryo Extract Demethylates Tumor Suppressor Genes in Osteosarcoma Cells

“…Our previous study has demonstrated strong oxidative stress resistance of K7M2 cells [31]. PI staining of K7M2 cells incubated with hydrogen peroxide (H 2 O 2 ) displayed significantly increased percentages of apoptotic cells (PI-positive) in K7M2 cells after 2 days of CEE treatment compared with cells without CEE treatment (Fig.…”

“…P53 is also involved in osteosarcoma tumorigenesis [12,18], and epigenetic alterations of this gene contribute to the pathogenesis of osteosarcoma [35]. E-cadherin performs a key role in cell adhesion, and loss of E-cadherin is known as a key step leading to tumor metastasis [3,31,32]. Negative expression of E-cadherin was found to be correlated with higher metastasis and a shorter overall survival in human patients with osteosarcoma [24].…”

Aldehyde dehydrogenase induction in arsenic-exposed rat bladder epithelium

“…CSCs have protection mechanisms against oxidative stress, which can cause a resistance to cancer therapy. Studies have found that K7M2 cells, a high-ALDH-activity osteosarcoma (OS) cell line, have the ability of resist oxidative stress and invasive and oncogenic factor expression when compared with K12 cells (Mu et al, 2013). Thus, ALDH activity in cancer cells can neutralize oxidative stress and provide resistance to chemo-or radiotherapy.…”

Osteosarcomagenesis: Biology, Development, Metastasis, and Mechanisms of Pain

“…Targeted inhibition of the signaling pathway of mTOR has been shown to reduce metastatic behavior in a mouse model of osteosarcoma [79] as well as human xenograft models [80]. Current and future clinical trials using mTOR inhibitors may prove therapeutically fruitful in the treatment of osteosarcoma [81].…”