CHEMORESISTANCE RELATED TO HYPOXIA ADAPTATION IN MESOTHELIOMA CELLS FROM TUMOR SPHEROIDS.

BACKGROUND

Hypoxia has been noted as a key factor for induction and maintenance of cancer stemness thereby leading to therapy resistance. Three-dimensional (3D) spheroid models demonstrate a heterogeneity of hypoxic regions replicating the in vivo situation within tumors. Utilizing an established 3D spheroid model, we investigated whether extrinsic hypoxia reinforced chemoresistance in malignant pleural mesothelioma (MPM) spheroids.

MATERIALS AND METHODS

Tumor spheres were generated from Meso-1 (a typical human MPM cell line) cells having high spheroid-forming ability. To induce hypoxia condition, we utilized a hypoxia chamber with regulation of O2 and CO2 levels. Cell viability was estimated by a WST-8 assay. Real-time polymerase chain reaction and Western blot were performed to evaluate the expression at mRNA and protein levels.

RESULTS

Compared with cells cultured in the two-dimensional monolayer model, tumor sphere cells showed elevated mRNA levels of cancer stemness markers (CD26, CD44 and ABCG2) and protein levels of the stemness and hypoxia adaptation markers (ABCG2, ALDH1A1 and HIFs). Correlating with this, 3D spheroid cells were more resistant to permetrexed and topotecan than the two-dimensional cells, indicative of their potential for hypoxic adaptation. Furthermore, significantly stronger resistance to both chemotherapeutic agents was observed in spheroid cells upon hypoxic challenge compared to spheroid cells under normoxia.

CONCLUSION

From the present data, it is concluded that hypoxia adaptation of MPM cells from tumor spheres could enhance their chemoresistance.