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A Multiplexed Luciferase-based Screening Platform for Interrogating Cancer-associated Signal Transduction in Cultured Cells
Published on: July 3, 2013
Degradome-focused RNA interference screens to identify proteases important for breast cancer cell growth
Lena Hölzen1,2,3,4, Kerstin Syré1, Jan Mitschke5
1Institute of Molecular Medicine and Cell Research, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
Abstract:
Proteases are known to promote or impair breast cancer progression and metastasis. However, while a small number of the 588 human and 672 murine protease genes have been extensively studied, others were neglected. For an unbiased functional analysis of all genome-encoded proteases, i.e., the degradome, in breast cancer cell growth, we applied an inducible RNA interference library for protease-focused genetic screens. Importantly, these functional screens were performed in two phenotypically different murine breast cancer cell lines, including one stem cell-like cell line that showed phenotypic plasticity under changed nutrient and oxygen availability. Our unbiased genetic screens identified 252 protease genes involved in breast cancer cell growth that were further restricted to 100 hits by a selection process. Many of those hits were supported by literature, but some proteases were novel in their functional link to breast cancer. Interestingly, we discovered that the environmental conditions influence the degree of breast cancer cell dependency on certain proteases. For example, breast cancer stem cell-like cells were less susceptible to depletion of several mitochondrial proteases in hypoxic conditions. From the 100 hits, nine proteases were functionally validated in murine breast cancer cell lines using individual knockdown constructs, highlighting the high reliability of our screens. Specifically, we focused on mitochondrial processing peptidase (MPP) subunits alpha (Pmpca) and beta (Pmpcb) and discovered that MPP depletion led to a disadvantage in cell growth, which was linked to mitochondrial dysfunction.
Insights
This study screened all proteases in breast cancer cells, identifying 100 key genes involved in cell growth. Environmental conditions impact cancer cell dependence on these proteases, with mitochondrial proteases being crucial.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Proteases play a dual role in breast cancer progression and metastasis.
- The functional roles of many protease genes in breast cancer remain largely uncharacterized.
Purpose of the Study:
- To conduct an unbiased, genome-wide functional analysis of the degradome in breast cancer cell growth.
- To identify novel proteases involved in breast cancer and understand environmental influences on protease dependency.
Main Methods:
- Utilized an inducible RNA interference library for protease-focused genetic screens in two distinct murine breast cancer cell lines.
- Performed functional screens under varying nutrient and oxygen conditions, including in stem cell-like lines with phenotypic plasticity.
- Validated key protease hits using individual knockdown constructs.
Main Results:
- Identified 252 protease genes involved in breast cancer cell growth, narrowed down to 100 significant hits.
- Discovered that environmental conditions modulate breast cancer cell dependence on specific proteases, notably in hypoxic conditions for stem-like cells.
- Functionally validated nine proteases, confirming the reliability of the screens.
- Demonstrated that depletion of mitochondrial processing peptidase (MPP) subunits (Pmpca, Pmpcb) impairs cell growth due to mitochondrial dysfunction.
Conclusions:
- The degradome contains numerous uncharacterized proteases critical for breast cancer cell growth.
- Breast cancer cell dependency on proteases is context-dependent, influenced by microenvironmental factors like oxygen levels.
- Mitochondrial processing peptidase (MPP) is a validated target, highlighting the role of mitochondrial proteases in breast cancer progression.
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