The role of SET/I2PP2A in canine mammary tumors

Area of Science:

• Oncology
• Molecular Biology
• Veterinary Medicine

Background:

• Canine mammary tumors (CMTs) are common in female dogs and serve as a translational model for human breast cancer.
• Serine/threonine protein phosphatase 2A (PP2A) acts as a tumor suppressor, and its activity is regulated by endogenous inhibitors like SET/I2PP2A.
• SET protein directly binds and inhibits PP2A phosphatase activity.

Purpose of the Study:

• To investigate the role of SET in canine mammary tumor progression.
• To determine the impact of SET on tumor sensitivity to existing therapeutics.
• To elucidate the signaling pathways influenced by SET in canine mammary tumors.

Main Methods:

• Analysis of SET protein levels in canine mammary tumor tissues.
• Knockdown of SET expression in the CIP-m canine mammary tumor cell line.
• Assessment of cell proliferation, colony formation, and in vivo tumor growth after SET knockdown.
• Evaluation of signaling pathways including mTOR, β-catenin, and NFκB.
• Testing the sensitivity of SET-knockdown cells to various chemotherapeutics and radiation.

Main Results:

• Elevated SET protein levels were found in advanced-stage canine mammary tumors.
• SET knockdown in CIP-m cells increased PP2A activity, reduced cell proliferation, colony formation, and in vivo tumor growth.
• SET knockdown suppressed mTOR, β-catenin, and NFκB signaling pathways.
• SET knockdown decreased sensitivity to doxorubicin but did not affect sensitivity to 4-OH-tamoxifen, carboplatin, bortezomib, or X-ray radiation.

Conclusions:

• SET plays a significant role in the progression of a subset of canine mammary tumors by inhibiting PP2A activity.
• SET enhances tumor growth through the activation of mTOR, β-catenin, and NFκB signaling pathways.
• Targeting SET may offer a therapeutic strategy for canine mammary tumors, potentially influencing response to certain chemotherapies like doxorubicin.