Radiolabeled probes targeting hypoxia-inducible factor-1-active tumor microenvironments

Area light source-triggered latent angiogenic molecular mechanisms intensify therapeutic efficacy of adult stem cells

Light-based therapy such as photobiomodulation (PBM) reportedly produces beneficial physiological effects in cells and tissues. However, most reports have focused on the immediate and instant effects of light. Considering the physiological effects of natural light exposure in living organisms, the latent reaction period after irradiation should be deliberated. In contrast to previous reports, we examined the latent reaction period after light exposure with optimized irradiating parameters and validated novel therapeutic molecular mechanisms for the first time. we demonstrated an organic light-emitting diode (OLED)-based PBM (OPBM) strategy that enhances the angiogenic efficacy of human adipose-derived stem cells (hADSCs) via direct irradiation with red OLEDs of optimized wavelength, voltage, current, luminance, and duration, and investigated the underlying molecular mechanisms. Our results revealed that the angiogenic paracrine effect, viability, and adhesion of hADSCs were significantly intensified by our OPBM strategy. Following OPBM treatment, significant changes were observed in HIF-1α expression, intracellular reactive oxygen species levels, activation of the receptor tyrosine kinase, and glycolytic pathways in hADSCs. In addition, transplantation of OLED-irradiated hADSCs resulted in significantly enhanced limb salvage ratio in a mouse model of hindlimb ischemia. Our OPBM might serve as a new paradigm for stem cell culture systems to develop cell-based therapies in the future.

18F-fluoromisonidazole positron emission tomography may be applicable in the evaluation of colorectal cancer liver metastasis

BACKGROUND

Positron emission tomography (PET) imaging is a non-invasive functional imaging method used to reflect tumor spatial information, and to provide biological characteristics of tumor progression. The aim of this study was to focus on the application of ¹⁸F-fluoromisonidazole (FMISO) PET quantitative parameter of maximum standardized uptake value (SUVmax) ratio to detect the liver metastatic potential of human colorectal cancer (CRC) in mice.

METHODS

Colorectal liver metastases (CRLM) xenograft models were established by injecting tumor cells (LoVo, HT29 and HCT116) into spleen of mice, tumor-bearing xenograft models were established by subcutaneously injecting tumor cells in the right left flank of mice. Wound healing assays were performed to examine the ability of cell migration in vitro. ¹⁸F-FMISO uptake in CRC cell lines was measured by cellular uptake assay. ¹⁸F-FMISO-based micro-PET imaging of CRLM and tumor-bearing mice was performed and quantified by tumor-to-liver SUVmax ratio. The correlation between the ¹⁸F-FMISO SUVmax ratio, liver metastases number, hypoxia-induced factor 1α (HIF-1α) and serum starvation-induced glucose transporter 1 (GLUT-1) was evaluated using Pearson correlation analysis.

RESULTS

Compared with HT29 and HCT116, LoVo-CRLM mice had significantly higher liver metastases ratio and shorter median survival time. LoVo cells exhibited stronger migration capacity and higher radiotracer uptake compared with HT29 and HCT116 in in vitro. Moreover, ¹⁸F-FMISO SUVmax ratio was significantly higher in both LoVo-CRLM model and LoVo-bearing tumor model compared to models established using HT29 and HCT116. In addition, Pearson correlation analysis revealed a significant correlation between ¹⁸F-FMISO SUVmax ratio of CRLM mice and number of liver metastases larger than 0.5 cm, as well as between ¹⁸F-FMISO SUVmax ratio and HIF-1α or GLUT-1 expression in tumor-bearing tissues.

CONCLUSIONS

¹⁸F-FMISO parameter of SUVmax ratio may provide useful tumor biological information in mice with CRLM, thus allowing for better prediction of CRLM and yielding useful radioactive markers for predicting liver metastasis potential in CRC.

Anti-angiogenic effect of rapamycin in mouse oxygen-induced retinopathy is mediated through suppression of HIF-1alpha/VEGF pathway

Hypoxia-inducible factor-1alpha (HIF-1α)-vascular endothelial growth factor (VEGF) pathway, a downstream of mammalian target of rapamycin (mTOR), plays a major role in the formation of pathological retinal angiogenesis. Rapamycin (RAPA), a highly specific inhibitor of mTOR, is widely used in cancer studies for its antiangiogenic activity. However, the inhibitory effects of RAPA on the HIF-1α-VEGF pathway in retinal tissues were rarely researched. The study aimed to investigate the efficacy and potential mechanisms of RAPA in inhibiting retinal neovascularization. Human umbilical vein endothelial cells (HUVECs) were treated with hypoxia and in the presence of different concentrations of RAPA. RAPA was injected intraperitoneally in oxygen-induced retinopathy (OIR) C57BL/6 mice from postnatal day 12 (P12) to P17. The proliferation of HUVECs, the protein and mRNA expressions of HIF-1α and VEGF were evaluated in HUVECs or OIR mice using MTT assay, ELISA, immunohistochemistry, Western-blot and real-time PCR. Histological methods were used to count blood vessel profiles in the inner retina. RAPA inhibited HUVECs proliferation and retinal neovascularization by reducing protein and mRNA expressions of HIF-1α and VEGF. RAPA suppresses hypoxia-induced HUVECs cell proliferation and pathological ocular angiogenesis through a mechanism linked to the targeting of HIF-1α/VEGF signaling.