Mitochondria play important roles in angiogenesis. However, the mechanisms remain elusive. In this study, we found that mitochondrial ubiquinol-cytochrome c reductase complex assembly factor 3 (UQCC3) is a key regulator of angiogenesis. TALEN-mediated knockout of Uqcc3 in mice caused embryonic lethality at 9.5-10.5 days postcoitum, and vessel density was dramatically reduced. Similarly, knockout of uqcc3 in zebrafish induced lethality post-fertilization and impaired vascular development. Knockout of UQCC3 resulted in slower tumor growth and angiogenesis. Mechanistically, UQCC3 was upregulated under hypoxia, promoted reactive oxygen species (ROS) generation, enhanced HIF-1 alpha stability and increased VEGF expression. Finally, higher expression of UQCC3 was associated with poor prognosis in multiple types tumors, implying a role for UQCC3 in tumor progression. In conclusion, our findings highlight the important contribution of UQCC3 to angiogenesis under both physiological and pathological conditions, indicating the potential of UQCC3 as a therapeutic target for cancer.

Angiogensis during embryonic development and tumor growth requires the crucial involvement of mitochondria, which provide energy for cell proliferation, produce angiogenic signaling molecules, and exhibit a different functional profile in these cells. However, the detailed mechanisms underlying the regulatory role of mitochondria in angiogenesis remain elusive and warrant. Here, we reported that a small assembly factor of complex III, ubiquitin-cytochrome c reductase complex assembly factor 3 (UQCC3), is indispensable for angiogenesis during embryonic development and tumor growth. Homozygous deletion of UQCC3 caused early embryonic lethality and impaired vascular development. UQCC3 knockout in tumor cells impaired tumor angiogenesis and inhibits tumor growth. Mechanistically, UQCC3 expression was significantly upregulated in a hypoxic environment, which stabilised hypoxia inducible factor-1α (HIF-1α) and provoked a significantly higher expression of VEGF. UQCC3 knockout reduced the production of mitochondrial reactive oxygen species (ROS), stabilzed HIF-1α, and VEGF expression, but supplementation of ROS can restore HIF-1α and VEGF levels, and vice versa. Finally, based on the analysis of TCGA database, having high levels of UQCC3 is associated with unfavorable outcomes across various types of tumors, indicating a significant role for UQCC3 in tumor progression.

The 'angiogenic switch' is critical for tumor progression. However, the pathological details and molecular mechanisms remain incompletely characterized. In this study, we established mammal xenografts in zebrafish to visually investigate the first vessel growth (angiogenic switch) in real-time, by inoculating tumor cells into the perivitelline space of live optically transparent Transgenic (flk1:EGFP) zebrafish larvae. Using this model, we found that hypoxia and hypoxia-inducible factor (HIF) signaling were unnecessary for the angiogenic switch, whereas vascular endothelial growth factor A gene (Vegfa) played a crucial role. Mechanistically, transcriptome analysis showed that the angiogenic switch was characterized by inhibition of translation, but not hypoxia. Phosphorylation of eukaryotic translation initiation factor 2 alpha (Eif2α) and the expression of Vegfa were increased in the angiogenic switch microtumors, and 3D tumor spheroids, and puromycin-treated tumor cells. Vegfa overexpression promoted early onset of the angiogenic switch, whereas Vegfa knockout prevented the first tumor vessel from sprouting. Pretreatment of tumor cells with puromycin promoted the angiogenic switch in vivo similarly to Vegfa overexpression, whereas Vegfa knockdown suppressed the increase. This study provides direc and dynamic in vivo evidences that inhibition of translation, but not hypoxia or HIF signaling promotes the angiogenic switch in tumor by increasing Vegfa transcription.

The treatment of large established tumors remains a significant challenge and is generally hampered by poor drug penetration and intrinsic drug resistance of tumor cells in the central tumor region. In the present study, we developed bacterial particles (BactPs) to deliver chemotherapeutics into the tumor mass by hijacking neutrophils as natural cell-based carriers. BactPs loaded with doxorubicin, 5-fluorosuracil, or paclitaxel induced significantly greater tumor regression than unconjugated drugs. This effect was mediated by the ability of BactPs to incorporate chemotherapeutics and serve as vascular disrupting agents that trigger innate host responses and recruit phagocytic neutrophils. Vascular disruption resulted in extensive cell death in the central areas of the tumor mass. Recruited neutrophils acted as natural cellular carriers to deliver engulfed BactPs, which ensured drug delivery into the tumor mass and cytotoxic effects in areas that are normally inaccessible to traditional chemotherapy. Thus, BactPs eradicate large established tumors by functioning as vascular disrupters and natural drug carriers for neutrophil-mediated chemotherapy.

Bioenergetic reprogramming during hypoxia adaption is critical to promote hepatocellular carcinoma (HCC) growth and progression. However, the mechanism underlying the orchestration of mitochondrial OXPHOS (oxidative phosphorylation) and glycolysis in hypoxia is not fully understood. Here, we report that mitochondrial UQCC3 (C11orf83) expression increases in hypoxia and correlates with the poor prognosis of HCC patients. Loss of UQCC3 impairs HCC cell proliferation in hypoxia in vitro and in vivo. Mechanistically, UQCC3 forms a positive feedback loop with mitochondrial reactive oxygen species (ROS) to sustain UQCC3 expression and ROS generation in hypoxic HCC cells and subsequently maintains mitochondrial structure and function and stabilizes HIF-1α expression to enhance glycolysis under hypoxia. Thus, UQCC3 plays an indispensable role for bioenergetic reprogramming of HCC cells during hypoxia adaption by simultaneously regulating OXPHOS and glycolysis. The positive feedback between UQCC3 and ROS indicates a self-modulating model within mitochondria that initiates the adaptation of HCC to hypoxic stress.

Due to hypoxia and poor circulation in the tumor interior, malignant cells in solid tumors are resistant to traditional therapies. In the present study, we reported that bacterial particles (BactPs) functioned effectively in retarding tumor growth as a novel vascular disrupting agent. The BactPs were inactivated intact bacteria. Intravenous administration of BactPs extensively disrupted vessels in the tumor interior, but not in normal organs, and resulted in tumor hemorrhage and necrosis in six hours. We revealed that the extensive disruption of tumor vasculature was due to drastic changes in the inflammatory factors in mice sera and the tumor microenvironments, indicating the critical role of the host immune response to the BactPs. Furthermore, we showed that a combination of six inflammatory cytokines was capable of inducing tumor hemorrhage and necrosis, similar to the effects of the BactPs. Together, these results suggest that BactPs are a novel kind of tumor vascular disruptor with a promising potential for solid tumor treatment.

BACKGROUND AND AIMS:Hyperlipidemia-induced atherosclerosis is the major cause of heart attack and stroke in humans. However, pathological details and molecular mechanisms underlying early atherogenesis remain incompletely characterized. This study explored the early events of atherogenesis in a hypercholesterolemic zebrafish model in vivo.METHODS:We used transparent transgenic zebrafish larvae Tg(lysc:EGFP), Tg(mpx:EGFP), Tg(mpeg1:EGFP), Tg(flk1:EGFP) or Tg(lysc:EGFP/flk1:mCherry), together with fluorescently labeled control and high cholesterol diets (HCD), to dynamically investigate the early development of atherosclerosis with confocal in vivo. Endothelial cells with green fluorescence were sorted by fluorescence-activated cell sorting (FACS) to detect gene expression. Moreover, we treated hypercholesterolemic zebrafish model in vivo or human umbilical vein endothelial cells (HUVEC) in vitro with rosiglitazone, an agonist of peroxisome proliferator-activated receptor γ (PPARγ).RESULTS:We found that HCD-induced endothelial inflammation was an earlier pathological alteration than myeloid cells/neutrophils accumulation and lipid deposition in zebrafish vascular vessels of HCD-fed zebrafish. Endothelial inflammation was characterized by down-regulation of anti-inflammatory PPARγ and upregulation of pro-inflammatory tumor necrosis factor α (TNF-α) and interleukin-1β (IL-1β). Pharmacological treatment with rosiglitazone reversed the decrease in the expression of PPARγ and decreased expression of TNF-α and IL-1β in HCD-fed zebrafish. Moreover, rosiglitazone ameliorated myeloid cells accumulation and lipid deposition in HCD-fed zebrafish in vivo.CONCLUSIONS:Hyperlipidemia-induced endothelial inflammation happens earlier than myeloid cell neutrophils accumulation in vascular vessels, and neutrophils accumulation is prior to lipid deposition during the initial stage of atherosclerosis. Early alleviation of inflammation induced by HCD would have a prophylactic effect for the initial development of atherosclerosis.