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Mitochondrial stress-induced calcium signaling, phenotypic changes and invasive behavior in human lung carcinoma A549
Govindasamy Amuthan1, Gopa Biswas, Hindupur K Ananadatheerthavarada
1Department of Animal Biology and Mari Lowe Center for Comparative Oncology School of Veterinary Medicine, University of Pennsylvania 3800 Spruce Street, Philadelphia, PA 19104-6047, USA.
Abstract:
We have investigated mechanisms of mitochondrial stress-induced phenotypic changes and cell invasion in tumorigenic but poorly invasive human pulmonary carcinoma A549 cells that were partly depleted of mitochondrial DNA (mtDNA). Depletion of mtDNA (genetic stress) caused a markedly lower electron transport-coupled ATP synthesis, loss of mitochondrial membrane potential, elevation of steady state [Ca(2+)](c), and notably induction of both glycolysis and gluconeogenic pathway enzymes. Markers of tumor invasion, cathepsin L and TGFbeta1, were overexpressed; calcium-dependent MAP kinases (ERK1 and ERK2) and calcineurin were activated. The levels of anti-apoptotic proteins Bcl2 and Bcl-X(L) were increased, and the cellular levels of pro-apoptotic proteins Bid and Bax were reduced. Both mtDNA-depleted cells (genetic stress) and control cells treated with carbonyl cyanide m-chlorophenylhydrazone (metabolic stress) exhibited higher invasive behavior than control cells in a Matrigel basement membrane matrix assay system. MtDNA-depleted cells stably expressing anti-sense cathepsin L RNA, TGFbeta1 RNA, or treated with specific inhibitors showed reduced invasion. Reverted cells with 80% of control cell mtDNA exhibited marker protein levels, cell morphology and invasive property closer to control cells. Our results suggest that the mitochondria-to-nucleus signaling pathway operating through increased [Ca(2+)](c) plays an important role in cancer progression and metastasis.
Insights
Mitochondrial DNA depletion in lung cancer cells enhances invasion by altering cell metabolism and activating cancer progression pathways. This suggests mitochondria-to-nucleus signaling is crucial for metastasis.
Area of Science:
- Cell Biology
- Cancer Research
- Mitochondrial Biology
Background:
- Mitochondrial dysfunction is implicated in various diseases, including cancer.
- The role of mitochondrial DNA (mtDNA) depletion in cancer cell invasion and metastasis requires further elucidation.
Purpose of the Study:
- To investigate the mechanisms of mitochondrial stress-induced phenotypic changes and cell invasion in human pulmonary carcinoma A549 cells.
- To explore the role of mitochondria-to-nucleus signaling in cancer progression and metastasis.
Main Methods:
- Partial depletion of mitochondrial DNA (mtDNA) in A549 cells to induce genetic stress.
- Assessment of cellular bioenergetics, calcium signaling, and expression of invasion markers.
- Matrigel invasion assays and manipulation of specific gene expression (cathepsin L, TGFbeta1).
Main Results:
- mtDNA depletion led to reduced ATP synthesis, loss of mitochondrial membrane potential, and elevated intracellular calcium ([Ca(2+)](c)).
- Glycolysis and gluconeogenic pathways were induced, alongside overexpression of cathepsin L and TGFbeta1, and activation of MAP kinases.
- Both genetic (mtDNA depletion) and metabolic stress increased cell invasion, which was reduced by inhibiting key invasion markers.
Conclusions:
- Mitochondrial stress significantly alters cellular metabolism and promotes invasive phenotypes in lung cancer cells.
- Mitochondria-to-nucleus signaling, mediated by increased [Ca(2+)](c), plays a critical role in driving cancer progression and metastasis.