Proteasome inhibition with bortezomib suppresses growth and induces apoptosis in osteosarcoma

Abstract

Osteosarcomas are primary bone tumors of osteoblastic origin that mostly affect adolescent patients. These tumors are highly aggressive and metastatic. Previous reports indicate that gain of function of a key osteoblastic differentiation factor, Runx2, leads to growth inhibition in osteosarcoma. We have previously established that Runx2 transcriptionally regulates expression of a major proapoptotic factor, Bax. Runx2 is regulated via proteasomal degradation, and proteasome inhibition has a stimulatory effect on Runx2. In this study, we hypothesized that proteasome inhibition will induce Runx2 and Runx2-dependent Bax expression sensitizing osteosarcoma cells to apoptosis. Our data showed that a proteasome inhibitor, bortezomib, increased Runx2 and Bax in osteosarcoma cells. In vitro, bortezomib suppressed growth and induced apoptosis in osteosarcoma cells but not in nonmalignant osteoblasts. Experiments involving intratibial tumor xenografts in nude mice demonstrated significant tumor regression in bortezomib-treated animals. Immunohistochemical studies revealed that bortezomib inhibited cell proliferation and induced apoptosis in osteosarcoma xenografts. These effects correlated with increased immunoreactivity for Runx2 and Bax. In summary, our results indicate that bortezomib suppresses growth and induces apoptosis in osteosarcoma in vitro and in vivo suggesting that proteasome inhibition may be effective as an adjuvant to current treatment regimens for these tumors. Published 2009 UICC.

Characterization of canine osteosarcoma by array comparative genomic hybridization and RT‐qPCR: Signatures of genomic imbalance in canine osteosarcoma parallel the human counterpart

“…Of specific interest is the gene RUNX2, which resides within the orthologous regions defined by HSA 6p21.1 and CFA 12q13. Several recent studies have focused on investigating the dysregulation of RUNX2 in human OS Sadikovic et al, 2009Sadikovic et al, , 2010San Martin et al, 2009;Shapovalov et al, 2010), and the comparability of our data suggests that RUNX2 merits further investigation in both species.…”

Arsenic trioxide induces programmed cell death through stimulation of ER stress and inhibition of the ubiquitin–proteasome system in human sarcoma cells

“…The accumulated data have revealed that targeting UPS components such as proteasomes offers great promise as a novel therapeutic strategy for cancer [34,35]. When newly synthesized proteins in the ER do not present a correct folding, they are translocated to the cytosol where they are immediately subjected to proteasomal degradation [13].…”

Mitochondrial Dysfunction and Permeability Transition in Osteosarcoma Cells Showing the Warburg Effect

“…These OS cell lines have been extensively characterized by our group, as evident from our previous studies (8,25,28). Importantly, the LM7 cell line is an invasive and metastatic subtype of the parental Saos2 cell line (29), and the 143B cell line is an invasive and metastatic subtype of the parental HOS cell line (30).…”

“…Electron Microscopy-Cultured cells or tissue pieces of xenografted OS tumors produced as described in our previous study (25) were fixed in 2.5% glutaraldehyde in 0.1 M sodium cacodylate buffer, post-fixed in 1.0% OsO 4 , dehydrated with ethanol, and transitioned into propylene oxide for infiltration and embedding into EPON/Araldite epoxy resin. Thin sections were cut onto grids, stained with uranyl acetate and lead citrate, examined with a Hitachi H-7650 transmission electron microscope, and digitally photographed.…”