PPARγ attenuates cancer cell migration and invasion through activation of small GTPase protein, Cdc42 / Rac1 in pancreatic cancer Free

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Background and Aims:

Peroxisome Proliferator Activated Receptor-γ (PPARγ) is known to aberrantly express in many kinds of cancer cells including pancreatic carcinoma, although the mutation of PPARγ is rare. Therefore, we hypothesized that PPARγ played the important roles in cancer progression and invasion. To address this issue, we investigated the inhibitory effect of PPARγ in pancreatic cancer cells.

Methods:

Pancreatic cancer cell lines (Capan-1, Panc-1) were obtained from the American Type Culture Collection.

Cell motility was assessed using transwell migration and wound healing assay. In these assay, cancer cells were treated with the PPARγ inhibitor (T0070907. 0.01~1.0μM) and small interfering RNA, and after incubation, the number of migrated cells was counted and wounds were photographed.

Immunofluorescent staining of p120-catenin (p120-ctn) was performed using confocal microscopy. In order to quantities of Cdc42 or Rac1 activity, cells were lysed and small GTPases were collected by the agarose beads with PAK-1 and measured the amount of these proteins by western blotting. To assay metastatic abilities, viable pancreatic cancer cells inoculated into the pancreas of SCID mice directly. The mice were treated with oral feeding with T007090. The mice were killed 4 weeks after inoculation, and the volume and numbers of liver metastasis were counted.

Results:

Transwell migration assay showed that T0070907 significantly decreased the number of migration cells in the dose dependent manner. In the wound healing assay, the wound healings were inhibited with T0070907 or siRNA treatment. On the other side, T0070907 (0.01-1.0 μM) didn’t influence cell proliferation in the MTT assay.
 >Confocal microscopy findings demonstrated that p120-ctn moved to cell membrane from cytoplasm when T0070907 (0.1μM)was added. And the activity of Cdc42 and Rac1 were reduced with T0070907 treatment because they were activated by p120-ctn.
 >In vivo assay, liver metastasis of pancreatic cancer cells were significantly reduced with T0070907 treatment in the xenograft mice model
 >Conclusions:
 >Inhibition of PPARγ decreased motility of both pancreatic cancer cells, but not influence their proliferation at the concentration of 0.01-1.0 μM.
 >We speculate PPARγ plays an important role for retaining p120-ctn in the cytosoplasm. In addition, the inhibition of PPARγ decrease the activity of small GTPase protein indirectly. We conclude PPARγ attenuates pancreatic cancer cell migration, invasion and metastasis.