Possible involvement of stem-like populations with elevated ALDH1 in sarcomas for chemotherapeutic drug resistance

Abstract

Abstract. Elevated aldehyde dehydrogenase 1 (ALDH1) has been proposed as one of the possible candidates for a stem cell maker that can be used for the isolation of cancer stem cells from cancers such as leukemia and breast cancer. In the current study, we found that subpopulations with elevated ALDH1 were present in the human sarcoma cell lines, MG63 (osteosarcoma) and HT1080 (fibrosarcoma), using Aldefluor assay. Both ALDH1 positive and negative cell populations were isolated from the MG63 cell line, by cell-sorting using FACSAria. Both subpopulations had a comparable ability to differentiate similarly to the parental MG63, under normal monolayer culture condition. Subpopulations with the ability to form spheres in anchorage-independent, serum-starved conditions showed increased ALDH1 mRNA expression in addition to strong mRNA expression of the stem cell-related genes, such as Nanog, Oct3/4, Stat3 and Sox2, and possessed ability for self-renewal with secondary sphere formation. Sarcosphere cells from the MG63 cell line showed strong chemo-resistance against both doxorubicin and cisplatin compared with monolayer, adherent cells. In conclusion, sphere-forming cells with elevated ALDH1 are a possible candidate for sarcoma stem cells, possessing strong chemoresistant capacities. Although ALDH1 elevation was not sufficient for representing sarcoma stem cells, the efficient detoxification could contribute to the chemo-resistant properties of the stem-like sphere cells form human sarcoma.

Identification of chemoradiation-resistant osteosarcoma stem cells using an imaging system for proteasome activity

“…The sphere-forming capacity in established osteosarcoma cell lines has been previously demonstrated (4,8,9,11,12). Interestingly, Honoki et al showed that the frequency of sphere formation was 0.25% in ALDH1-positive MG-63 cells (9). Moreover, primary cultures of osteosarcoma tended to have enhanced sphere-forming capacities (5,8,16).…”

“…The proteasome activity of ZsGreen + cells are lower than ZsGreen -cells in MG-63, whereas no difference was found in U2-OS; this is likely because this proteasome activity assay can detect partial proteasome activity. The sphere-forming capacity in established osteosarcoma cell lines has been previously demonstrated (4,8,9,11,12). Interestingly, Honoki et al showed that the frequency of sphere formation was 0.25% in ALDH1-positive MG-63 cells (9).…”

“…Identification of osteosarcoma TICs has been performed using CD133 (4,5), side populations (6,7), PKH26 (8), ALDH1 (9,10), and the promoter reporter assays of hTERT (11) and Oct3/4 (12). TIC-enriched osteosarcoma cell populations exhibit capacity for self-renewal, multilineage differentiation, tumorigenicity, Identification of chemoradiation-resistant osteosarcoma stem cells using an imaging system for proteasome activity and chemo-and radioresistance.…”

Cancer stem cells in osteosarcoma

“…A subpopulation of ALDH1 high MG63 cells was detected by Honoki et al (25) who further reported ALDH1 high cells to have increased expression of stem-like genes (Nanog, Oct3/4, Stat3, Sox2), higher resistance to doxorubicin and cisplatin and increased self-renewal ability as shown by sphere formation. Importantly, ALDH high cells were also detected in human osteosarcoma samples and increased ALDH activity was further correlated to metastatic potential (26).…”

Distinctive properties of metastasis-initiating cells

“…Therefore, the generation of MIC properties may be phenotypically linked to enhanced drug resistance capacities. MICs enriched with CSC-like features may benefit from resistant mechanisms of CSCs, such as a stronger DNA damage response (Wang 2015), elevated expression of efflux drug pumps (Schinkel et al 1994;Zhou et al 2001;Dean et al 2005), and ALDH detoxifying enzymes (Honoki et al 2010;Rausch et al 2010). Therefore, inhibitors of pathways involved in CSC regulation, such as antibodies against NOTCH, FZD, IL6R, and other relevant signaling pathway receptors, may also have a therapeutic impact on MICs (Brooks et al 2015).…”