shRNA kinome screen identifies TBK1 as a therapeutic target for HER2+ breast cancer

Area of Science:

• Oncology
• Molecular Biology
• Cancer Therapeutics

Background:

• HER2(+) breast cancer treatment with chemotherapy and anti-HER2 inhibitors faces challenges due to non-response and relapse.
• Tumor-initiating cells (TICs) are implicated in treatment resistance and disease recurrence in HER2(+) breast cancer.
• There is a critical need for novel therapeutics targeting TICs to improve outcomes for HER2(+) breast cancer patients.

Purpose of the Study:

• To identify novel therapeutic targets, particularly those affecting TICs, that can overcome resistance to current HER2(+) breast cancer treatments.
• To screen for kinases that play a role in maintaining TICs in HER2(+) breast cancer.
• To evaluate the therapeutic potential of inhibiting identified kinases, alone and in combination with existing therapies.

Main Methods:

• Utilized MMTV-Her2/Neu mammary tumor cells cultured in sphere and monolayer conditions to isolate and maintain TICs.
• Employed a lentivirus short hairpin RNA kinome library screen in p53-mutant Her2/Neu(+) tumorsphere cells to identify key kinases.
• Investigated the role of TANK-binding kinase 1 (TBK1) and IKKε in HER2(+) breast cancer cell growth, senescence, and apoptosis, both in vitro and in vivo xenograft models.
• Assessed the combination therapy effect of TBK1/IKKε inhibition with lapatinib.

Main Results:

• Identified TBK1 and IKKε as novel kinases involved in HER2(+) breast cancer, distinct from previously implicated pathways.
• Knockdown or pharmacologic inhibition of TBK1/IKKε suppressed the growth of both mouse and human HER2(+) breast cancer cells.
• TBK1/IKKε inhibition induced cellular senescence by suppressing p65-NF-κB and upregulating p16(Ink4a).
• Combination therapy of TBK1/IKKε inhibitors with lapatinib accelerated apoptosis and eradicated HER2(+) breast cancer cells in vitro and in vivo.

Conclusions:

• TBK1 and IKKε are crucial targets for HER2(+) breast cancer therapy, particularly for overcoming resistance and targeting TICs.
• Combined inhibition of TBK1/IKKε and HER2 (e.g., with lapatinib) offers a promising therapeutic strategy for HER2(+) breast cancer.
• The study establishes a screening platform for identifying additional TIC-specific inhibitors for HER2(+) breast cancer treatment.