Heme Binding Biguanides Target Cytochrome P450-Dependent Cancer Cell Mitochondria.

The mechanisms by which cancer cell-intrinsic CYP monooxygenases promote tumor progression are largely unknown. CYP3A4 was unexpectedly associated with breast cancer mitochondria and synthesized arachidonic acid (AA)-derived epoxyeicosatrienoic acids (EETs), which promoted the electron transport chain/respiration and inhibited AMPKα. CYP3A4 knockdown activated AMPKα, promoted autophagy, and prevented mammary tumor formation. The diabetes drug metformin inhibited CYP3A4-mediated EET biosynthesis and depleted cancer cell-intrinsic EETs. Metformin bound to the active-site heme of CYP3A4 in a co-crystal structure, establishing CYP3A4 as a biguanide target. Structure-based design led to discovery of N1-hexyl-N5-benzyl-biguanide (HBB), which bound to the CYP3A4 heme with higher affinity than metformin. HBB potently and specifically inhibited CYP3A4 AA epoxygenase activity. HBB also inhibited growth of established ER+ mammary tumors and suppressed intratumoral mTOR. CYP3A4 AA epoxygenase inhibition by biguanides thus demonstrates convergence between eicosanoid activity in mitochondria and biguanide action in cancer, opening a new avenue for cancer drug discovery.

Combining Multiple Types of Motor Rehabilitation Enhances Skilled Forelimb Use Following Experimental Traumatic Brain Injury in Rats.

BACKGROUND: Neuroplasticity and neurorehabilitation have been extensively studied in animal models of stroke to guide clinical rehabilitation of stroke patients. Similar studies focused on traumatic brain injury (TBI) are lacking. OBJECTIVE: The current study was designed to examine the effects of individual and combined rehabilitative approaches, previously shown to be beneficial following stroke, in an animal model of moderate/severe TBI, the controlled cortical impact (CCI). METHODS: Rats received a unilateral CCI, followed by reach training, voluntary exercise, or unimpaired forelimb constraint, alone or in combination. Forelimb function was assessed at different time points post-CCI by tests of skilled reaching, motor coordination, and asymmetrical limb use. RESULTS: Following CCI, skilled reaching and motor coordination were significantly enhanced by combinations of rehabilitation strategies, not by individual approaches. The return of symmetrical limb use benefited from forelimb constraint alone. None of the rehabilitation strategies affected the size of injury, suggesting that enhanced behavioral function was not a result of neuroprotection. CONCLUSIONS: The current study has provided evidence that individual rehabilitation strategies shown to be beneficial in animal models of stroke are not similarly sufficient to enhance behavioral outcome in a model of TBI. Motor rehabilitation strategies for TBI patients may need to be more intense and varied. Future basic science studies exploring the underlying mechanisms of combined rehabilitation approaches in TBI as well as clinical studies comparing rehabilitation approaches for stroke versus TBI would prove fruitful.

Effect of genistein on p90RSK phosphorylation and cell proliferation in T47D breast cancer cells.

BACKGROUND: The molecular mechanisms of genistein's proliferative effects on breast cancer cells are largely unknown. This study aimed to examine estrogen-receptor (ER)-related signaling molecules involved in genistein-associated cell proliferation and survival (ERK1/2, p90RSK, JNK, Akt and NFκB) and to correlate these results to cell proliferation. MATERIALS AND METHODS: The effect of genistein on cell-signaling molecules was determined in T47D breast cancer cells by a Bioplex phosphoprotein detection kit. These results were confirmed by Western blotting and were correlated to cell proliferation by MTT assay. RESULTS: Low and high concentrations of genistein induced an ERK1/2-independent decrease in phosphorylated p90RSK. This effect was accompanied by decreased cell proliferation at high concentrations and an increased response at low concentrations of genistein following a 48-hour exposure. CONCLUSION: Concentration-dependent actions of genistein in T47D cells may be due to differential activation of signaling molecules.