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Resistance development after long-term sorafenib exposure in hepatocellular cancer cell lines and risk of rebound growth and epithelial to mesenchymal transition.
J Clin Oncol 30, 2012 (suppl 4; abstr 216)
Abstracts that were granted an exception in accordance with ASCO's Conflict of Interest Policy are designated with a caret symbol (^).
Background: Sorafenib, a multi tyrosine kinase inhibitor, is the first line treatment in patients with advanced hepatocellular carcinoma (HCC). It leads to a survival benefit but treatment with sorafenib is hampered by two phenomena: patients can develop important side-effects and eventually all patients show progression. We aimed to determine the effects of long-term exposure to sorafenib and its withdrawal in vitro. Methods: We developed sorafenib resistant liver cancer cell lines (HepG2, WRL-68 and Huh-7) by slowly increasing sorafenib concentrations. XTT- and BrdU-assay were used to study the effect of sorafenib withdrawal on proliferation and metabolism. Morphological changes were examined with immuocytochemistry, gene expression changes with RT-PCR and the invasive potential with matrigel invasion chambers. Microarray was performed on resistant HepG2 cells. Results: HepG2 cells (6µM), WRL-68 cells (6µM) and Huh-7 cells (5µM) became resistant to sorafenib. Resistance was confirmed with a shift of the IC50 to ±16µM and ongoing phosphorylation of ERK during sorafenib exposure. All three resistant cell types showed significant increased proliferation and metabolic activity after withdrawal of sorafenib. The HepG2 resistant cells have undergone an epithelial to mesenchymal transition (EMT) with loss of E-cadherin and high expression of vimentin. The cells that displayed EMT became spindle shaped and were highly invasive. Furthermore, gene expression profiling confirmed EMT changes in a large set of EMT-related genes. Considering drug metabolism, the HepG2 sorafenib resistant cells showed a downregulation of UDP glucuronosyltransferases (UGT) and cytochromes P450, such as CYP3A4. There was a strong downregulation of different ABC-transporters, although breast cancer resistance protein (ABCG2) was upregulated. Conclusions: Long-term treatment with sorafenib can lead to the development of resistant cells, even with an aggressive phenotype because the cells can undergo EMT. Furthermore we demonstrated that abrogation of treatment leads to rebound growth, suggesting the importance of aggressive management of side-effects.
Abstracts by Chris Verslype:
Phase II randomized trial of MEK inhibitor pimasertib or placebo combined with gemcitabine in the first-line treatment of metastatic pancreatic cancer.
Safety and activity of ziv-aflibercept in combination with irinotecan, 5-fluorouracil, and leucovorin (FOLFIRI) in patients with colorectal cancer previously treated with irinotecan: Results from a phase 1 study.
Sorafenib in combination with local microtherapy guided by gadolinium-EOB-DTPA enhanced MRI in patients with inoperable hepatocellular carcinoma (SORAMIC).