HIF-1 activation induces doxorubicin resistance in MCF7 3-D spheroids via P-glycoprotein expression: a potential model of the chemo-resistance of invasive micropapillary carcinoma of the breast

• Main Authors: Doublier Sophie, Belisario Dimas C, Polimeni Manuela, Annaratone Laura, Riganti Chiara, Allia Elena, Ghigo Dario, Bosia Amalia, Sapino Anna
• Format: Article
• Language: English
• Published: BMC 2012-01-01
• Series: BMC Cancer
• Subjects: HIF-1α; 3-D spheroids, Elastase; Invasive micropapillary breast carcinoma; Doxorubicin resistance; P-glycoprotein; MUC-1
• Online Access: http://www.biomedcentral.com/1471-2407/12/4

<p>Abstract</p> <p>Background</p> <p>Invasive micropapillary carcinoma (IMPC) of the breast is a distinct and aggressive variant of luminal type B breast cancer that does not respond to neoadjuvant chemotherapy. It is characterized by small pseudopapillary clusters of cancer cells with inverted cell polarity. To investigate whether hypoxia-inducible factor-1 (HIF-1) activation may be related to the drug resistance described in this tumor, we used MCF7 cancer cells cultured as 3-D spheroids, which morphologically simulate IMPC cell clusters.</p> <p>Methods</p> <p>HIF-1 activation was measured by EMSA and ELISA in MCF7 3-D spheroids and MCF7 monolayers. Binding of HIF-1α to <it>MDR-1 </it>gene promoter and modulation of P-glycoprotein (Pgp) expression was evaluated by ChIP assay and FACS analysis, respectively. Intracellular doxorubicin retention was measured by spectrofluorimetric assay and drug cytotoxicity by annexin V-FITC measurement and caspase activity assay.</p> <p>Results</p> <p>In MCF7 3-D spheroids HIF-1 was activated and recruited to participate to the transcriptional activity of <it>MDR-1 </it>gene, coding for Pgp. In addition, Pgp expression on the surface of cells obtained from 3-D spheroids was increased. MCF7 3-D spheroids accumulate less doxorubicin and are less sensitive to its cytotoxic effects than MCF7 cells cultured as monolayer. Finally, HIF-1α inhibition either by incubating cells with 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (a widely used HIF-1α inhibitor) or by transfecting cells with specific siRNA for HIF-1α significantly decreased the expression of Pgp on the surface of cells and increased the intracellular doxorubicin accumulation in MCF7 3-D spheroids.</p> <p>Conclusions</p> <p>MCF7 breast cancer cells cultured as 3-D spheroids are resistant to doxorubicin and this resistance is associated with an increased Pgp expression in the plasma membrane via activation of HIF-1. The same mechanism may be suggested for IMPC drug resistance.</p>