Antiproliferative small-molecule inhibitors of transcription factor LSF reveal oncogene addiction to LSF in hepatocellular carcinoma

Abstract

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide. Despite the prevalence of HCC, there is no effective, systemic treatment. The transcription factor LSF is a promising protein target for chemotherapy; it is highly expressed in HCC patient samples and cell lines, and promotes oncogenesis in rodent xenograft models of HCC. Here, we identify small molecules that effectively inhibit LSF cellular activity. The lead compound, factor quinolinone inhibitor 1 (FQI1), inhibits LSF DNA-binding activity both in vitro, as determined by electrophoretic mobility shift assays, and in cells, as determined by ChIP. Consistent with such inhibition, FQI1 eliminates transcriptional stimulation of LSF-dependent reporter constructs. FQI1 also exhibits antiproliferative activity in multiple cell lines. In LSF-overexpressing cells, including HCC cells, cell death is rapidly induced; however, primary or immortalized hepatocytes are unaffected by treatment with FQI1. The highly concordant structure–activity relationship of a panel of 23 quinolinones strongly suggests that the growth inhibitory activity is due to a single biological target or family. Coupled with the striking agreement between the concentrations required for antiproliferative activity (GI 50 s) and for inhibition of LSF transactivation (IC 50 s), we conclude that LSF is the specific biological target of FQIs. Based on these in vitro results, we tested the efficacy of FQI1 in inhibiting HCC tumor growth in a mouse xenograft model. As a single agent, tumor growth was dramatically inhibited with no observable general tissue cytotoxicity. These findings support the further development of LSF inhibitors for cancer chemotherapy.

Drug Resistance Mediated by AEG-1/MTDH/LYRIC

“…In addition to TS, LSF transcribes several genes associated with aggressive cancers, including osteopontin (OPN), MMP9, MET, and complement factor H (CFH) (Yoo et al, 2011b). A high-throughput screen identified factor quinolinone inhibitor 1 (FQI1) as an LSF DNA binding inhibitor that induces apoptosis and inhibits proliferation of HCC cells (Grant et al, 2012). Because specific inhibitors to target AEG-1/MTDH/LYRIC have not been identified, inhibiting AEG-1/MTDH/LYRIC downstream effector LSF may provide a new strategy to treat HCC.…”

“…Because specific inhibitors to target AEG-1/MTDH/LYRIC have not been identified, inhibiting AEG-1/MTDH/LYRIC downstream effector LSF may provide a new strategy to treat HCC. Indeed, LSF may very well represent an “Achilles heel” for HCC given the addiction to LSF for survival (Grant et al, 2012). …”

Targeting the oncogene LSF with either the small molecule inhibitor FQI1 or siRNA causes mitotic delays with unaligned chromosomes, resulting in cell death or senescence

“…In all cases, inhibition of tumor growth occurred in the absence of toxicity, as assessed by liver injury markers, histopathology of tissues with rapid cell turnover, or blood cell counts (18). These results suggested that hepatocellular carcinoma cells are oncogene addicted to LSF (14,19).…”

“…A family of small molecule inhibitors of LSF, Factor Quinolinone Inhibitors (FQIs), was identified that inhibits the DNA binding and transcription activity of LSF, but not that of transcription factors from multiple other structural classes (14). Activity of p53, the closest structural relative of the LSF family (15,16), was also not inhibited by FQIs.…”

AEG-1/MTDH/LYRIC in Liver Cancer

“…A high-throughput screening identified small-molecule inhibitors of LSF DNA binding and the prototype of these molecules, Factor quinolinone inhibitor 1 (FQI1), profoundly inhibited cell viability and induced apoptosis in human HCC cells without exerting harmful effects to normal immortal human hepatocytes and primary mouse hepatocytes (Grant et al, 2012). In nude mice xenograft studies, FQI1 markedly inhibited growth of human HCC xenografts as well as angiogenesis without exerting any toxicity.…”