Sequential drug delivery by injectable macroporous hydrogels for combined photodynamic-chemotherapy

With hollow mesoporous silica (hMSN) and injectable macroporous hydrogel (Gel) used as the internal and external drug-loading material respectively, a sequential drug delivery system DOX-CA4P@Gel was constructed, in which combretastatin A4 phosphate (CA4P) and doxorubicin (DOX) were both loaded. The anti-angiogenic drug, CA4P was initially released due to the degradation of Gel, followed by the anti-cell proliferative drug, DOX, released from hMSN in tumor microenvironment. Results showed that CA4P was mainly released at the early stage. At 48 h, CA4P release reached 71.08%, while DOX was only 24.39%. At 144 h, CA4P was 78.20%, while DOX release significantly increased to 61.60%, showing an obvious sequential release behavior. Photodynamic properties of porphyrin endow hydrogel (ϕΔ(Gel) = 0.91) with enhanced tumor therapy effect. In vitro and in vivo experiments showed that dual drugs treated groups have better tumor inhibition than solo drug under near infrared laser irradiation, indicating the effectivity of combined photodynamic-chemotherapy.

Synergistic Anticancer Effects of Cisplatin Combined with Combretastatin A4 Phosphate on Human Osteosarcoma-Xenografted Mice

This study aimed to investigate the effectiveness of anticancer therapy combining a cytotoxic chemotherapeutic agent, cisplatin (DDP), and a vascular disruptive drug, combretastatin A4 phosphate (CA4P), in osteosarcoma. First, a human osteosarcoma-xenografted mice model was established. Second, the transplanted tumor models were treated with DDP and CA4P in combination or as monotherapy. Third, the therapeutic effects and the mechanism of the drug combination in the inhibition of transplanted tumors was studied. Finally, the toxic effects of the drugs were observed and recorded. The results showed that DDP combined with CA4P significantly inhibited the growth and lung metastasis of transplanted tumors compared with the monotherapy drug group and vehicle control group. Histopathological analysis revealed that apoptotic and necrotic cell death significantly increased in the combination group, and combined treatment significantly inhibited the proliferation of osteosarcoma cells compared with either agent alone or the vehicle control. Additionally, no obvious toxic effects were observed in the combination group. These results indicate that the combined effects of DDP and CA4P on the progression of human osteosarcoma in vivo were superior to that of either agent alone. DDP combined with CA4P exerted synergistic effects at lower concentrations and promoted apoptosis and necrosis, as well as inhibited proliferation of osteosarcoma cells, but it did not increase the systemic toxic effects of chemotherapy. Our findings highlight CA4P as an effective anticancer agent candidate for combination with DDP in clinical applications to treat osteosarcoma.

Intra-individual comparison of therapeutic responses to vascular disrupting agent CA4P between rodent primary and secondary liver cancers

AIM

To compare therapeutic responses of a vascular-disrupting-agent, combretastatin-A4-phosphate (CA4P), among hepatocellular carcinomas (HCCs) and implanted rhabdomyosarcoma (R1) in the same rats by magnetic-resonance-imaging (MRI), microangiography and histopathology.

METHODS

Thirty-six HCCs were created by diethylnitrosamine gavage in 14 rats that were also intrahepatically implanted with one R1 per rat as monitored by T2-/T1-weighted images (T2WI/T1WI) on a 3.0T clinical MRI-scanner. Vascular response and tumoral necrosis were detected by dynamic contrast-enhanced (DCE-) and CE-MRI before, 1 h after and 12 h after CA4P iv at 10 mg/kg (treatment group n = 7) or phosphate-buffered saline at 1.0 mL/kg (control group n = 7). Tumor blood supply was calculated by a semiquantitative DCE parameter of area under the time signal intensity curve (AUC30). In vivo MRI findings were verified by postmortem techniques.

RESULTS

On CE-T1WIs, unlike the negative response in all tumors of control animals, in treatment group CA4P caused rapid extensive vascular shutdown in all R1-tumors, but mildly or spottily in HCCs at 1 h. Consequently, tumor necrosis occurred massively in R1-tumors but patchily in HCCs at 12 h. AUC30 revealed vascular closure (66%) in R1-tumors at 1 h (P < 0.05), followed by further perfusion decrease at 12 h (P < 0.01), while less significant vascular clogging occurred in HCCs. Histomorphologically, CA4P induced more extensive necrosis in R1-tumors (92.6%) than in HCCs (50.2%) (P < 0.01); tumor vascularity heterogeneously scored +~+++ in HCCs but homogeneously scored ++ in R1-tumors.

CONCLUSION

This study suggests superior performance of CA4P in metastatic over primary liver cancers, which could guide future clinical applications of vascular-disrupting-agents.​

Quantitative Evaluation of Combretastatin A4 Phosphate Early Efficacy in a Tumor Model with Dynamic Contrast-Enhanced Ultrasound

Combretastatin A4 phosphate (CA4P) is a vascular disrupting agent that rapidly shuts down blood supply to tumors. Early monitoring of tumor perfusion plays a crucial role in determining the optimal strategy to managing treatment and guiding future therapy. The aim of this study was to investigate the potential value of dynamic contrast-enhanced ultrasound (CEUS) in quantitative evaluation of tumor perfusion at an early stage in CA4P therapy. Central and peripheral perfusion of tumors was detected by CEUS pre-treatment (0 h) and 2, 12 and 48 h after CA4P injection. Two perfusion parameters, maximum intensity (IMAX) and time to peak (TTP), were calculated from the time-intensity curve. After CEUS, the efficacy of CA4P was immediately confirmed by immunofluorescence assay and hematoxylin and eosin, Hoechst 33342 and fluorescein isothiocyanate-lectin staining. In CEUS of the center region of tumors, IMAX gradually decreased from 0 to 12 h and regrew at 48 h (p < 0.01). TTP increased only at 2 h. In the peripheral regions, IMAX did not change obviously from 0 to 12 h (p > 0.05) and just increased at 48 h (p < 0.01). The TTP of peripheral regions had the same tendency to vary tendency as that of center regions. In addition, microvascular density (MVD), vascular perfusion and necrotic area of the tumor were quantitatively analyzed. A close correlation between IMAX and MVD was observed in the center areas of tumors (r = 0.72, p < 0.01), whereas the correlation between IMAX and MVD in peripheral areas was weak (r = 0.37, p < 0.01). However, IMAX was positively correlated with tumor perfusion in both center and peripheral areas of tumors (r = 0.82, p < 0.01, and r = 0.63, p < 0.01, respectively). Consequently, IMAX was a reliable indicator of tumor perfusion evaluation by CEUS. The use of CEUS to quantify tumor perfusion could a promising method for the early detection of tumor responses in anti-vascular treatment.