The C2 Domain of PKC‑δ as a Dominant-Negative Modulator of Breast Cancer Cell Survival and Chemosensitivity

Area of Science:

• Molecular Biology
• Cancer Research
• Cell Biology

Background:

• Protein Kinase C-δ (PKC-δ) is implicated in breast cancer progression and resistance to therapy.
• PKC-δ activation involves diacylglycerol or proteolytic cleavage, exposing its catalytic site.
• The C2 domain of PKC-δ regulates kinase activity through protein-protein interactions.

Purpose of the Study:

• To investigate the autonomous effects of the PKC-δ C2 domain in hormone-dependent (MCF-7) and triple-negative (MDA-MB-468) breast cancer cells.
• To assess the impact of C2 domain overexpression on cell viability, apoptosis, and proliferation.
• To determine the role of the C2 domain in sensitizing breast cancer cells to oxidative and genotoxic stress.

Main Methods:

• Stable overexpression of a myc-tagged PKC-δ C2 domain (myc-δC2) in MCF-7 and MDA-MB-468 cell lines.
• Assessment of cell viability, apoptosis, and proliferation.
• Evaluation of cell cycle progression (G2/M arrest) and cell size.
• Testing sensitization to hydrogen peroxide (H₂O₂) and etoposide, with and without dasatinib pretreatment.

Main Results:

• myc-δC2 expression reduced cell viability and increased apoptosis in both cell lines.
• MCF-7 cells exhibited G2/M arrest and increased cell size, unlike MDA-MB-468 cells.
• MCF-7 cells showed consistent sensitization to stress, while MDA-MB-468 cells required higher stress levels or dasatinib pretreatment for sensitization.

Conclusions:

• The isolated PKC-δ C2 domain has a cell line-dependent pro-death function in breast cancer.
• Modulating the PKC-δ C2 domain could represent a novel therapeutic approach for breast cancer.
• The C2 domain may serve as an autonomous pro-apoptotic agent in specific breast cancer contexts.