Bevacizumab inhibits proliferation of choroidal endothelial cells by regulation of the cell cycle

EIGHTEEN-MONTH RESULTS OF INTRAVITREAL ANTI-VASCULAR ENDOTHELIAL GROWTH FACTOR ON VISION AND MICROCIRCULATION IN RADIATION MACULOPATHY

PURPOSE

To evaluate 18 months' results of a strict anti-vascular endothelial growth factor protocol for radiation maculopathy following proton therapy in choroidal melanoma.

METHODS

Retrospective, comparative, nonrandomized study of 74 radiation maculopathy patients presenting macular lipid deposits, hemorrhages, microaneurysms, cystoid edema, nerve layer infarction, telangiectasia, or capillary nonperfusion. The study group included 52 consecutive patients injected with intravitreal anti-vascular endothelial growth factors (bevacizumab/ranibizumab: 46/6) every two months for the first and every 3 months for the second year, with minimum 12 months' follow-up. The control group consisted of 22 patients having declined this treatment. Best-corrected visual acuity, spectral domain-optical coherence tomography and optical coherence tomography angiography were recorded at baseline, 6, 12, and 18 months. The foveal avascular zone and capillary density were measured at the superficial capillary plexus.

RESULTS

Radiation maculopathy was diagnosed at 2 years (1.5-3.5) after proton therapy. Best-corrected visual acuity at baseline, 12 and 18 months improved in the study group from 0.45, 0.3 to 0.2 logarithm of the minimum angle of resolution, but decreased in the control group from 0.5, 0.9 to 1.0 logarithm of the minimum angle of resolution respectively (P < 0.001 at 12 months). Simultaneously, foveal avascular zone enlargement was less in the study (from 0.377, 0.665 to 0.744 mm2) than control group (from 0.436, 1.463 to 2.638 mm2) (P = 0.05 at 12 months). CMT (280 and 276 µm) and capillary density (37% and 38%, at baseline, respectively) did not evolve significantly different.

CONCLUSION

Intravitreal anti-vascular endothelial growth factors, every 2 months for the first and every 3 months for the second year, slow down, over up to 18 months, vision loss and anatomical degradation in radiation maculopathy following proton therapy for choroidal melanoma.

Development of a Biocompatible Copolymer Nanocomplex to Deliver VEGF siRNA for Triple Negative Breast Cancer

Triple negative breast cancer (TNBC) is the most difficult breast cancer subtype to treat. TNBC patients have significantly higher expression of vascular endothelial growth factor (VEGF) in tumors compared to non-TNBC patients. VEGF not only exerts its pro-angiogenic effects on endothelial cells but also acts as a survival and autocrine growth factor for VEGF receptor (VEGFR) expressing cancer cells. Silencing the expression of VEGF is therefore a potential therapy for TNBC.

Methods: A novel biocompatible linear copolymer poly[bis(ε-Lys-PEI)Glut-PEG] (PLEGP) was developed to deliver VEGF siRNA for TNBC therapy. The copolymer is composed of lysine and glutaric acid, a natural metabolite of amino acids in the body. Low-molecular weight polyethyleneimine (PEI) was grafted to the copolymer to efficiently condense siRNA into nanocomplex without inducing cytotoxicity. Various in vitro studies were performed to evaluate the stability, cellular uptake, tumor penetration, and biological activities of the VEGF siRNA nanocomplex. The anti-tumor activities of the nanocomplex was also evaluated in an orthotopic TNBC mouse model.

Results: PEIs with different molecular weights were evaluated, and the copolymer PLEGP₁₈₀₀ was able to easily form a stable nanocomplex with siRNAs and protect them from serum degradation. The siRNA/PLEGP₁₈₀₀ nanocomplex exhibited negligible cytotoxicity but showed high cellular uptake, high transfection efficiency, and high tumor penetration. In vitro activity studies showed that the siRNA nanocomplex significantly inhibited migration and invasion of TNBC cells. Moreover, the VEGF siRNA nanocomplex efficiently inhibited tumor growth in an orthotopic TNBC mouse model and down-regulated VEGF expression in the tumor.

Conclusion: PLEGP₁₈₀₀ is a safe and efficient copolymer to deliver siRNAs for TNBC therapy. It could potentially be applied to other cancers by changing the cargo and incorporating tumor-specific ligands.

Inhibition of proliferation of retinal vascular endothelial cells more effectively than choroidal vascular endothelial cell proliferation by bevacizumab

AIM

To evaluate the differential inhibitory effects of bevacizumab on cell proliferation of vascular endothelial growth factor (VEGF)-stimulated choroidal vascular endothelial cells (CVECs) and retinal vascular endothelial cells (RVECs) in vitro.

METHODS

VEGF (400 ng/mL) enriched CVECs and RVECs were treated with escalating doses of bevacizumab (0.1, 0.5, 1, 1.5 and 2 mg/mL). Cell proliferation changes were analyzed with WST-1 assay and trypan blue exclusion assay at 48, 72h and 1wk. Morphological changes were recorded with bright field microscopy.

RESULTS

VEGF enriched RVECs showed significantly more decline of cell viability than CVECs after bevacizumab treatment. One week after treatment, RVEC cell proliferation decreased by 29.7%, 37.5%, 52.8%, 35.9% and 45.6% at 0.1, 0.5, 1.0, 1.5 and 2 mg/mL bevacizumab respectively compared to CVEC proliferation decrease of 4.1%, 7.7%, 2.4%, 4.1% and 17.7% (P<0.05) by WST-1 assay. Trypan blue exclusion assay also revealed similar decrease in RVEC proliferation of 20%, 60%, 73.3%, 80% and 93.3% compared to CVEC proliferation decrease of 4%, 12%, 22.9%, 16.7% and 22.2% respectively (P<0.05). The maximum differential effect between the two cell types was observed at bevacizumab doses of 1.0 and 1.5 mg/mL at all time points. RVECs were 22 fold more sensitive (P<0.01) compared to CVECs (52.8% vs 2.4%) at concentration of 1.0 mg/mL, and 8.7 fold more at 1.5 mg/mL (35.9% vs 4.1%) 1wk after treatment (P<0.05 respectively).

CONCLUSION

VEGF-enriched RVECs are more susceptible to bevacizumab inhibition than CVECs at clinically used dosage of 1.25 mg and this differential sensitivity between two cell types should be taken into consideration in dosage selection.

Endothelial TWIST1 promotes pathological ocular angiogenesis

PURPOSE

Pathological neovessel formation impacts many blinding vascular eye diseases. Identification of molecular signatures distinguishing pathological neovascularization from normal quiescent vessels is critical for developing new interventions. Twist-related protein 1 (TWIST1) is a transcription factor important in tumor and pulmonary angiogenesis. This study investigated the potential role of TWIST1 in modulating pathological ocular angiogenesis in mice.

METHODS

Twist1 expression and localization were analyzed in a mouse model of oxygen-induced retinopathy (OIR). Pathological ocular angiogenesis in Tie2-driven conditional Twist1 knockout mice were evaluated in both OIR and laser-induced choroidal neovascularization models. In addition, the effects of TWIST1 on angiogenesis and endothelial cell function were analyzed in sprouting assays of aortic rings and choroidal explants isolated from Twist1 knockout mice, and in human retinal microvascular endothelial cells treated with TWIST1 small interfering RNA (siRNA).

RESULTS

TWIST1 is highly enriched in pathological neovessels in OIR retinas. Conditional Tie2-driven depletion of Twist1 significantly suppressed pathological neovessels in OIR without impacting developmental retinal angiogenesis. In a laser-induced choroidal neovascularization model, Twist1 deficiency also resulted in significantly smaller lesions with decreased vascular leakage. In addition, loss of Twist1 significantly decreased vascular sprouting in both aortic ring and choroid explants. Knockdown of TWIST1 in endothelial cells led to dampened expression of vascular endothelial growth factor receptor 2 (VEGFR2) and decreased endothelial cell proliferation.

CONCLUSIONS

Our study suggests that TWIST1 is a novel regulator of pathologic ocular angiogenesis and may represent a new molecular target for developing potential therapeutic treatments to suppress pathological neovascularization in vascular eye diseases.

Exploring leptin antagonism in ophthalmic cell models

Background

Emerging evidence suggests that angiogenic and pro-inflammatory cytokine leptin might be implicated in ocular neovascularization. However, the potential of inhibiting leptin function in ophthalmic cells has never been explored. Here we assessed mitogenic, angiogenic, and signaling leptin activities in retinal and corneal endothelial cells and examined the capability of a specific leptin receptor (ObR) antagonist, Allo-aca, to inhibit these functions.

Methods and Results

The experiments were carried out in monkey retinal (RF/6A) and bovine corneal (BCE) endothelial cells. Leptin at 50-250 ng/mL stimulated the growth of both cell lines in a dose-dependent manner. The maximal mitogenic response (35±7 and 27±3% in RF6A and BCE cells, respectively) was noted at 24 h of 250 ng/mL leptin treatments. Leptin-dependent proliferation was reduced to base levels with 10 and 100 nM Allo-aca in BCE and RF6A cells, respectively. In both cell lines, leptin promoted angiogenic responses, with the maximal increase in tube formation (163±10 and 133±8% in RF6A and BCE cultures, respectively) observed under a 250 ng/mL leptin treatment for 3 h. Furthermore, in both cell lines 250 ng/mL leptin modulated the activity or expression of several signaling molecules involved in proliferation, inflammatory activity and angiogenesis, such as STAT3, Akt, and ERK1/2, COX2, and NFκB. In both cell lines, leptin-induced angiogenic and signaling responses were significantly inhibited with 100 nM Allo-aca. We also found that leptin increased its own mRNA and protein expression in both cell lines, and this autocrine effect was abolished by 100-250 nM Allo-aca.

Conclusions

Our data provide new insights into the role of leptin in ocular endothelial cells and represent the first original report on targeting ObR in ophthalmic cell models.