Characterization of the functional role of AMP-activated protein kinase in tumor suppression

abstractpublished_or_final_versionPathologyMasterMaster of Philosoph

IPA-3 Inhibits the Growth of Liver Cancer Cells By Suppressing PAK1 and NF-κB Activation

<div><p>Hepatocellular carcinoma (HCC) is one of the major malignancies worldwide and is associated with poor prognosis due to the high incidences of metastasis and tumor recurrence. Our previous study showed that overexpression of p21-activated protein kinase 1 (PAK1) is frequently observed in HCC and is associated with a more aggressive tumor behavior, suggesting that PAK1 is a potential therapeutic target in HCC. In the current study, an allosteric small molecule PAK1 inhibitor, IPA-3, was evaluated for the potential in suppressing hepatocarcinogenesis. Consistent with other reports, inhibition of PAK1 activity was observed in several human HCC cell lines treated with various dosages of IPA-3. Using cell proliferation, colony formation and BrdU incorporation assays, we demonstrated that IPA-3 treatment significantly inhibited the growth of HCC cells. The mechanisms through which IPA-3 treatment suppresses HCC cell growth are enhancement of apoptosis and blockage of activation of NF-κB. Furthermore, our data suggested that IPA-3 not only inhibits the HCC cell growth, but also suppresses the metastatic potential of HCC cells. Nude mouse xenograft assay demonstrated that IPA-3 treatment significantly reduced the tumor growth rate and decreased tumor volume, indicating that IPA-3 can suppress the <i>in vivo</i> tumor growth of HCC cells. Taken together, our demonstration of the potential preclinical efficacy of IPA-3 in HCC provides the rationale for cancer therapy.</p></div

IPA-3 suppressed cell proliferation.

<p>(A) The effect of IPA-3 on the cell proliferation rates of MIHA (upper, left panel), HepG2 (upper, middle panel) H2P (upper, right panel), H2M (lower, left panel) and MHCC97L (lower, right panel) cells. Statistical analysis was performed by comparing with the value of DMSO control. *<i>P</i><0.05, **<i>P</i><0.01 (ANOVA). (<b>B</b>) BrdU labeling assays of MIHA (upper, left panel), HepG2 (upper, middle panel), H2P (upper, right panel), H2M (lower, left panel) and MHCC97L (lower, right panel) cells. *<i>P</i><0.05 (ANOVA) compared with the DMSO control. Error bars, mean ± SD of triplicate samples. (<b>C</b>) Representative plates of colony formation assay of MIHA (left panel), HepG2 (middle panel) and H2M cells (right panel). Bar chart of colony formation assay (lower panel). *<i>P</i><0.001, **<i>P</i><0.01 (ANOVA) compared with the DMSO control. Error bars, mean ± SD of triplicate samples.</p

The suppressive effect of IPA-3 in nude mouse xenograft model.

<p>(<b>A</b>) MHCC97L cells were used for the xenograft model. Mice were treated three times weekly either with DMSO or IPA-3 (2 mg/kg or 4 mg/kg, i.p.). *<i>P</i><0.001 (ANOVA) compared with the DMSO control group. (<b>B</b>) Tumor weights were measured at the end of study. *<i>P</i><0.001, **<i>P</i><0.01, (ANOVA) compared with the DMSO control group. (<b>C</b>) Representative results of Western blotting analysis. P-PAK1 (T423), total PAK1, P-JNK and total JNK were detected. ***<i>P</i><0.05 (ANOVA) compared with the DMSO control. Error bars, mean ± SD of 5 animals per group.</p

The suppressive effect of IPA-3 on migration of H2M cells.

<p>(<b>A</b>) Paxillin protein expression was detected by immunofluorescence analysis under IPA-3 treatment. H2M and H2P (upper panel) cells were serum-starved overnight and treated with either DMSO control or IPA-3 (20 µM) for 15 minutes, followed by FBS replenishment for 10 minutes. Immunofluoresence signals of phalloidin (Red), paxillin (Green) and DAPI (Blue) represent stress fiber, focal adhesion and nucleus, respectively (magnification 40X). The number of focal adhesion (paxillin) were counted in H2M (lower, left panel) and H2P (lower, right panel), and represented in the bar chart. Error bars, mean ± SD of triplicate samples. *<i>P</i><0.01 (<i>t</i>-test) compared with DMSO control. (<b>B</b>) Western blotting analysis on the phosphorylation levels of PAK1 and paxillin. Serum-starved cells were treated with various concentrations of IPA-3 as indicated for 15 minutes, followed by FBS replenishment for 10 minutes. (<b>C</b>) Representative images of Transwell migration assay of H2M cells. Cells were treated with either DMSO or 10 µM IPA-3, and were allowed to migrate for 24 hours. Images show the cells having migrated to the lower chamber (upper panel). The number of migrated cells were counted and represented in the bar chart (lower panel). Error bars, mean ± SD of triplicate samples. *<i>P</i><0.01 (<i>t</i>-test) compared with DMSO control.</p