Abstract

--- - Introduction Lung cancer remains the leading cause of cancer-related mortality worldwide. Drug resistance is a major limitation of current therapies, prompting the search for new treatment strategies. Lung tumors frequently develop a hypoxic microenvironment associated with aggressive behavior and unfavorable clinical outcomes. Tumor-initiating cells (TICs), also known as cancer stem cells, and hypoxia-driven metabolic adaptations contribute significantly to therapy resistance. Mitochondrial destabilization has emerged as a promising invariant target in TICs. Triphenylphosphonium (TPP+)-conjugated hydroxybenzoates selectively accumulate in the mitochondrial matrix, driven by membrane potential, disrupting organelle function. Additionally, doxycycline inhibits mitochondrial biogenesis and reduces mitochondrial mass. Here, we evaluate a therapeutic strategy combining TPP+-conjugated lipophilic cations with doxycycline to target mitochondrial vulnerability in non-small cell lung cancer.Methods TPP+ lipophilic cations conjugated to benzoate derivatives, alone or combined with doxycycline, were evaluated for their ability to disrupt mitochondrial function, reduce cell viability, and induce apoptosis in two lung cancer cell lines under normoxic and hypoxic conditions.Results Our results demonstrate that these compounds exhibit cytotoxicity in lung cancer cells, particularly under hypoxic conditions, consistent with mitochondrial functional impairment. Combinations of TPP+C10/doxycycline and GA-TPP+C10/doxycycline exhibited synergistic cytotoxicity in both normoxia and hypoxia, and increased apoptotic cell death compared to monotherapies.Conclusion Targeting mitochondrial functions using mitochondria-directed compounds, particularly in combination with doxycycline, represents a promising therapeutic approach for lung cancer. This strategy may be especially effective in hypoxic microenvironments, where conventional therapies often fail. Further in vivo validation is warranted to support the translational potential of this approach. - Graphical abstract TPP + C10 accumulates in the mitochondrial matrix of lung cancer cells, where it disrupts mitochondrial function, alters oxidative metabolism, and induces metabolic stress. This triggers a compensatory increase in mitochondrial biogenesis and contributes to therapy resistance, particularly under hypoxic conditions. Doxycycline inhibits mitochondrial protein synthesis and biogenesis by targeting mitochondrial ribosomes. Combined treatment with TPP + C10 and doxycycline prevents adaptive mitochondrial renewal, leading to impaired energy production and enhanced tumor cell death. A diagram showing tumor cell evolution and targeted mitochondrial interference. The top section illustrates a light blue tumor cell transitioning under hypoxia into a darker, irregular cell with increased drug resistance. Below, a detailed mitochondrial magnification shows Doxycycline inhibiting pink ribosomes and TPP+C10 disrupting the membrane potential, indicated by positive and negative signs and H+ ions. The electron transport chain complexes (I-V) and the VDAC/HK-II glucose pathway are depicted on the membrane. Blue arrows track the combined treatment's flow, concluding in a red starburst icon on the right labeled "Cell death," signaling total metabolic collapse.