Disruption of caspase-independent cell proliferation pathway on spheroids (HeLa cells) treated with curcumin

Curcumin is an antiproliferative phytochemical extracted from <i>Curcuma longa L</i> and which has been studied in preclinical drug screening using cell monolayers and animal models. However, several limitations of these culture systems may be overcome by performing screening with three-dimensional (3-D) cell culture. The aim of this study was to investigate the effects of curcumin on cytotoxicity and genotoxicity as well as spheroid growth using cervical adenocarcinoma HeLa cell spheroids by performing RT-PCR mRNA expression of genes involved in cell death (<i>CASP3</i>, <i>CASP8</i>, <i>CASP9</i>, <i>PARP1</i>, <i>BBC3</i>, <i>BIRC5</i>, <i>BCL2</i>, <i>TNF</i>), autophagy (<i>BECN1, SQSTM1</i>), cell cycle regulation (<i>TP53</i>, <i>C-MYC</i>, <i>NF-kB</i>, <i>CDKN1A</i>, <i>m-TOR</i>, <i>TRAF-2</i>), DNA damage repair (<i>H2AFX</i>, <i>GADD45A, GADD45G</i>), oxidative stress (<i>GPX1</i>), reticulum stress (<i>EIF2AK3, ERN1</i>), and invasion (<i>MMP1</i>, <i>MMP9</i>) was investigated. Curcumin was cytotoxic in a concentration-dependent manner. Curcumin-treated spheroids exhibited lower proliferative recovery and cell proliferation attenuation, as observed in the clonogenic assay. Further, no marked genotoxicity was detected. Curcumin-treated spheroids displayed reduced expression of <i>BECN1</i> (2.9×), <i>CASP9</i> (2.1×), and <i>PARP1</i> (2.1×) mRNA. <i>PARP1</i> inhibition suggested disruption of essential pathways of proliferation maintenance. Downregulated expression of <i>CASP9</i> mRNA and unchanged expression of <i>CASP3/8</i> mRNA suggested caspase-independent cell death, whereas downregulated expression of <i>BECN1</i> mRNA indicated autophagic disruption. Therefore, curcumin exhibits the potential for drug development with antiproliferative activity to be considered for use in cancers.