KANK1 promotes breast cancer development by compromising Scribble-mediated Hippo activation

Area of Science:

• Cell Biology
• Cancer Research
• Molecular Oncology

Background:

• KANK1 (KN motif and ankyrin repeat domain 1) is expressed in epithelial cells, linking focal adhesions to microtubule complexes.
• In vitro studies suggest KANK1 suppresses cancer cell growth, yet TCGA data associates high KANK1 levels with poor prognosis in various malignancies.

Purpose of the Study:

• To resolve the discrepancy between in vitro and in vivo roles of KANK1 in cancer.
• To investigate the mechanism by which KANK1 influences tumor progression in vivo.

Main Methods:

• Utilized PyMT-transformed mammary tumor cells in vivo models.
• Investigated KANK1 localization and interactions within tumor cells.
• Assessed the impact of KANK1 on cell polarity, Hippo pathway activity, and TAZ (transcriptional coactivator with PDZ-binding motif) signaling.

Main Results:

• KANK1 promotes proliferation and survival of PyMT-transformed mammary tumor cells in vivo.
• KANK1 localizes to cell-cell junctions upon loss of basement membrane contact, competing with Scribble for NOS1AP binding.
• This competition inhibits Scribble's ability to activate the Hippo pathway, leading to TAZ stabilization and nuclear accumulation.

Conclusions:

• KANK1 acts as an oncoprotein in vivo, promoting breast cancer development by disrupting cell polarity and Hippo pathway signaling.
• The findings highlight KANK1's context-dependent role in cancer, with implications for understanding tumor progression and therapeutic strategies.