Nanodrugs Reprogram Cancer-Associated Fibroblasts and Normalize Tumor Vasculatures for Sequentially Enhancing Photodynamic Therapy of Hepatocellular Carcinoma

Background

The failure of cancer photodynamic therapy (PDT) is largely ascribed to excessive stroma and defective vasculatures that restrain the photosensitizer permeation and the oxygen perfusion in tumors.

Method and Results

In this study, a nanodrug that integrated the cancer-associated fibroblast (CAF) regulation with tumor vessel normalization was tailored to sequentially sensitize PDT. The nanodrug exhibited high targeting towards CAFs and efficiently reversed the activated CAFs into quiescence, thus decreasing collagen deposition in the tumor microenvironment (TME), which overcame the protective physical barrier. Furthermore, the nanodrug regulated vascular endothelial cells and restored the tumor vasculatures, thereby improving vascular permeability. Based on the combined effects of reprogramming the TME, the nanodrug improved tumor accumulation of photosensitizers and alleviated hypoxia in the TME, which facilitated the subsequent PDT. Importantly, the nanodrug regulated the immunosuppressive TME by favoring the infiltration of immunostimulatory cells over immunosuppressive cells, which potentiated the PDT-induced immune response.

Conclusion

Our work demonstrates a sequential treatment strategy in which the combination of the CAF regulation and tumor vasculature normalization, followed by PDT, could be a promising modality for sensitizing tumor to PDT.

Uncovering a Key Role of ETS1 on Vascular Abnormality in Glioblastoma

Glioblastoma (GBM) is the most aggressive type of brain tumor. Microvascular proliferation and abnormal vasculature are the hallmarks of the GBM, aggravating disease progression and increasing patient morbidity. Here, we uncovered a key role of ETS1 on vascular abnormality in glioblastoma. ETS1 was upregulated in endothelial cells from human tumors compared to endothelial cells from paired control brain tissue. Knockdown of Ets1 in mouse brain endothelial cells inhibited cell migration and proliferation, and suppressed expression of genes associated with vascular abnormality in GBM. ETS1 upregulation in tumor ECs was dependent on TGFβ signaling, and targeting TGFβ signaling by inhibitor decreased tumor angiogenesis and vascular abnormality in CT-2A glioma model. Our results identified ETS1 as a key factor regulating tumor angiogenesis, and suggested that TGFβ inhibition may suppress the vascular abnormality driven by ETS1.

Neurosurgical intraoperative ultrasonography using contrast enhanced superb microvascular imaging -vessel density and appearance time of the contrast agent

Background: Ultrasonography (US) provides real-time information on structures within the skull during neurosurgical operations. Superb microvascular imaging (SMI) is the latest imaging technique for detecting very low-velocity flow with minimal motion artifacts, and we have reported on this technique for intraoperative US monitoring. We combined SMI with administration of contrast agent to obtain detailed information during neurosurgical operations.Materials and methods: Twenty patients diagnosed with brain tumor (10 meningiomas, 5 glioblastomas, 2 hemangioblastomas, 1 schwannoma, 1 malignant lymphoma, 1 brain abscess) underwent neurosurgery under US with SMI and contrast agent techniques. Vessel density and appearance time following contrast administration were analyzed.Results: Flow in numerous vessels was not visualized by SMI alone, but appeared following injection of contrast agent in all cases. Flow in tumors was drastically enhanced by contrast agent in schwannoma, hemangioblastoma and meningioma, compared to normal brain tissue. Flows in the dilated and bent vessels of glioblastoma were also enhanced, although flow in hypoechoic lymphoma remained inconspicuous. The characteristics of tumor vessels were clearly visualized and tumor borders were demonstrated by the difference between tumor flow and brain flow, by the increased tumor vessel density and decreased appearance time of contrast agent compared to normal brain vessels.Conclusions: The combination of SMI and contrast agent techniques for intraoperative US monitoring could provide innovative flow images of tumor and normal brain. The neurosurgeon obtains information about tumor flow and tumor borderline before tumor resection.

Radiation-Induced Changes in Tumor Vessels and Microenvironment Contribute to Therapeutic Resistance in Glioblastoma

Glioblastoma (GBM) is a largely fatal and highly angiogenic malignancy with a median patient survival of just over 1 year with radiotherapy (RT). The effects of RT on GBM remain unclear, although increasing evidence suggests that RT-induced alterations in the brain microenvironment affect the recurrence and aggressiveness of GBM. Glioma stem cells (GSCs) in GBM are resistant to conventional therapies, including RT. This study aimed to investigate the effect of radiation on tumor growth and the GSC microenvironment in a mouse model of glioma. To evaluate the growth-inhibitory effects of ionizing radiation on GSCs, tumor volume was measured via anatomical magnetic resonance imaging (MRI) after the intracranial injection of 1 × 10⁴ human patient-derived GSCs (83NS cells), which exhibit marked radioresistance. When a tumor mass of ~5 mm³ was detected in each animal, 10 Gy of cranial irradiation was administered. Tumor progression was observed in the orthotopic xenografted GSC tumor (primary tumor) from a detectable tumor mass (5 mm³) to a lethal tumor mass (78 mm³) in ~7 d in the non-irradiated group. In the RT group, tumor growth was halted for almost 2 weeks after administering 10 Gy cranial irradiation, with tumor growth resuming thereafter and eventually approaching a lethal mass (56 mm³) 21 d after radiation. Radiation therapy yielded good therapeutic effects, with a 2-fold increase in GSC glioma survival; however, tumor relapse after RT resulted in higher mortality for the mice with a smaller tumor volume (p = 0.029) than the non-irradiated tumor-bearing mice. Moreover, tumor regrowth after IR resulted in different phenotypes associated with glioma aggressiveness compared with the non-irradiated mice; the apparent diffusion coefficient by diffusion MRI decreased significantly (p < 0.05, 0 Gy vs. 10 Gy) alongside decreased angiogenesis, abnormal vascular dilatation, and upregulated CD34, VWF, AQP1, and AQP4 expression in the tumor. These findings demonstrate that radiation affects GSCs in GBM, potentially resulting in therapeutic resistance by changing the tumor microenvironment. Thus, the results of this study suggest potential therapeutic targets for overcoming the resistance of GBMs to RT.

Apatinib, a selective VEGFR2 inhibitor, improves the delivery of chemotherapeutic agents to tumors by normalizing tumor vessels in LoVo colon cancer xenograft mice

Tumor vascular normalization has been proposed as a therapeutic strategy for malignant neoplasms, which can also interpret the synergistic effect of anti-angiogenesis agents combined with chemotherapy. Apatinib (Apa), a highly selective VEGFR2 inhibitor, attracts much attentions due to its encouraging anticancer activity, especially in the clinical trials of combined treatment. In this study, we investigated whether Apa could promote vascular normalization in tumor in a certain time window. Mice bearing LoVo colon cancer xenograft were orally administrated Apa (150 mg kg^-1 per day) for 5, 7, 10, or 12 days. Apa significantly inhibited tumor growth and decreased the microvessel density. Using multi-photon microscopy and electron microscopy, we found that Apa improved tumor vessel morphology by pruning distorted vessel branches and decreased the gap between endothelial cells after a 7-day treatment. Furthermore, Apa decreased vessel leakage and increased pericyte coverage on vascular endothelial cells, suggesting that tumor vessels were more mature and integrated. The intratumoral distribution of adriamycin (ADR) in Apa group was improved from day 7 to 10 without change in plasma drug concentration. Tumor blood perfusion was also increased in this window, and the expression of hypoxia induced factor 1α was downregulated, suggesting the effect of Apa on alleviating tumor hypoxic micro-environment. In conclusion, Apa may improve the effective perfusion of tumor vessels and increase the intratumoral distribution of ADR in a certain time window via normalizing tumor vessels. This normalization window (7 to 10 days of treatment) may contribute to develop a regimen of combined medication in clinic use of Apa.

Lipocalin-type prostaglandin D synthase-derived PGD2 attenuates malignant properties of tumor endothelial cells

Endothelial cells (ECs) are a key component of the tumor microenvironment. They have abnormal characteristics compared to the ECs in normal tissues. Here, we found a marked increase in lipocalin-type prostaglandin D synthase (L-PGDS) mRNA (Ptgds) expression in ECs isolated from mouse melanoma. Immunostaining of mouse melanoma revealed expression of L-PGDS protein in the ECs. In situ hybridization also showed L-PGDS (PTGDS) mRNA expression in the ECs of human melanoma and oral squamous cell carcinoma. In vitro experiments showed that stimulation with tumor cell-derived IL-1 and TNF-α increased L-PGDS mRNA expression and its product prostaglandin D₂ (PGD₂ ) in human normal ECs. We also investigated the contribution of L-PGDS-PGD₂ to tumor growth and vascularization. Systemic or EC-specific deficiency of L-PGDS accelerated the growth of melanoma in mice, whereas treatment with an agonist of the PGD₂ receptor, DP1 (BW245C, 0.1 mg/kg, injected intraperitoneally twice daily), attenuated it. Morphological and in vivo studies showed that endothelial L-PGDS deficiency resulted in functional changes of tumor ECs such as accelerated vascular hyperpermeability, angiogenesis, and endothelial-to-mesenchymal transition (EndMT) in tumors, which in turn reduced tumor cell apoptosis. These observations suggest that tumor cell-derived inflammatory cytokines increase L-PGDS expression and subsequent PGD₂ production in the tumor ECs. This PGD₂ acts as a negative regulator of the tumorigenic changes in tumor ECs. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Avastin® in combination with gemcitabine and cisplatin significantly inhibits tumor angiogenesis and increases the survival rate of human A549 tumor-bearing mice

The aim of this study was to investigate the effect of Avastin® in combination with gemcitabine and cisplatin (GP) on the tumor growth of A549 tumor-bearing mice and the potential anti-tumor mechanism. A total of 30 human A549 tumor-bearing nude mice were randomly divided into the Avastin, chemotherapy and combined treatment groups for treatment with an intraperitoneal injection of Avastin (5 mg/kg) (Avastin group); an intraperitoneal injection of gemcitabine (4 mg/kg) and cisplatin (4 mg/kg) (chemotherapy group); or intraperitoneal injections of Avastin and GP (combined treatment group). The mice were observed for 30 days and the tumor growth, survival and body weight of the mice in the three groups were analyzed. The protein level of vascular endothelial growth factor (VEGF) in the tumor tissues was analyzed by ELISA. The vascular density and structural changes of the tumor were analyzed using immunohistochemistry. Compared with the Avastin and chemotherapy groups, the tumor growth of mice in the combined treatment group was significantly inhibited, and the survival rate of the mice was increased significantly. No difference in body weight was observed among the three groups of mice (P>0.05). The levels of VEGF in the combined treatment group tumor tissues were significantly reduced compared with those in the chemotherapy group tumor tissues (P<0.05). Furthermore, the vessel density of the tumor tissue in the combined treatment group was significantly reduced compared with that in the chemotherapy group (P<0.05), and the number of normal vessels in the combined treatment group tumors was significantly higher than that in the chemotherapy group tumors after 7 days of treatment (P<0.05). In conclusion, Avastin can significantly decrease the level of VEGF in tumor tissue, inhibit tumor angiogenesis and promote the normalization of tumor vascular structure, which may explain the enhanced efficacy of Avastin in combination with chemotherapy.

Vaccination with vascular progenitor cells derived from induced pluripotent stem cells elicits antitumor immunity targeting vascular and tumor cells

Vaccination of BALB/c mice with dendritic cells (DCs) loaded with the lysate of induced vascular progenitor (iVP) cells derived from murine-induced pluripotent stem (iPS) cells significantly suppressed the tumor of CMS-4 fibrosarcomas and prolonged the survival of CMS-4-inoculated mice. This prophylactic antitumor activity was more potent than that of immunization with DCs loaded with iPS cells or CMS-4 tumor cells. Tumors developed slowly in mice vaccinated with DCs loaded with iVP cells (DC/iVP) and exhibited a limited vascular bed. Immunohistochemistry and a tomato-lectin perfusion study demonstrated that the tumors that developed in the iVP-immunized mice showed a marked decrease in tumor vasculature. Immunization with DC/iVP induced a potent suppressive effect on vascular-rich CMS-4 tumors, a weaker effect on BNL tumors with moderate vasculature, and nearly no effect on C26 tumors with poor vasculature. Treatment of DC/iVP-immunized mice with a monoclonal antibody against CD4 or CD8, but not anti-asialo GM1, inhibited the antitumor activity. CD8(+) T cells from DC/iVP-vaccinated mice showed significant cytotoxic activity against murine endothelial cells and CMS-4 cells, whereas CD8(+) T cells from DC/iPS-vaccinated mice did not. DNA microarray analysis showed that the products of 29 vasculature-associated genes shared between genes upregulated by differentiation from iPS cells into iVP cells and genes shared by iVP cells and isolated Flk-1(+) vascular cells in CMS-4 tumor tissue might be possible targets in the immune response. These results suggest that iVP cells from iPS cells could be used as a cancer vaccine targeting tumor vascular cells and tumor cells.

Evaluation of antivascular and antimitotic effects of tubulin binding agents in solid tumor therapy

Tubulin binding agents (TBAs) reduce tumor perfusion and inhibit mitosis of tumor cells in solid tumors, but it is not clear which effects contribute to the suppression of solid tumor growth. We evaluated the antivascular and antimitotic effects of several TBAs, combretastatin A-4 (CS A-4) phosphate, AC-7700, a novel CS A-4 derivative, colchicine, E7010, and vinblastine, on subcutaneous (s.c.) murine colon26 adenocarcinoma (c26). Tolerable doses of vinblastine and E7010) strongly inhibited tumor growth and induced mitotic arrest of tumor cells without affecting tumor perfusion. Colchicine had no effect on tumor growth and perfusion. When the injected dose was increased to the lethal range, however, these drugs markedly reduced tumor perfusion and caused necrosis of tumor tissue. Within the tolerable dose range, AC-7700 both strongly suppressed tumor growth and reduced tumor perfusion, and CS A-4 phosphate also exhibited a moderate antivascular effect. To evaluate the contribution of antivascular activity of TBAs to tumor growth suppression, excluding their direct cytotoxic effect on tumor cells, we established c26/acr, which is resistant to TBAs in vitro. Although E7010 showed a reduced suppressive effect on s.c. c26/acr tumor growth as compared with its effect on wild-type c26, AC-7700 remained potent against both cell lines. These results indicate that TBAs exert antivascular and antimitotic effects on solid tumors with marked differently effective dose ranges from agent to agent, and that the antivascular effect of TBAs inhibits solid tumor growth independently of the direct cytotoxic effect on tumor cells.

Antitumor effects due to irreversible stoppage of tumor tissue blood flow: evaluation of a novel combretastatin A-4 derivative, AC7700

The relation between tumor tissue blood flow (tBF) reduction and antitumor effects was investigated. Changes in tBF of normal tissues (liver, kidney cortex, bone marrow and brain cortex) and tumors (Yoshida sarcoma subline, LY80 and Sato lung carcinoma, SLC) due to i.v. administration of AC7700 (1, 3, 10 mg/kg), one of the combretastatin A-4 derivatives, were measured with the hydrogen clearance method. The change in blood flow in tumor microfoci was also observed directly using a rat transparent chamber. Chemotherapy against the solid tumors (LY80, SLC) was performed by administering AC7700 7 times at intervals of 3 days and the effect on the tumor growth, the histological effect, the effect on lymph node metastasis and the survival rate were investigated. Tumor tBF showed a dose-dependent response to AC7700. Although tumor tBF decreased markedly at a dose of 1 mg/kg, it tended to recover partly within several hours. At 10 mg/kg, however, tumor tBF completely stopped within approximately 30 min and never recovered in many regions. The irreversible stoppage of tumor tBF was observed in large s.c. tumors and in microfoci as well. On the other hand, in normal tissues, tBF changes due to AC7700 were not uniform. In the liver, although tBF decreased by approximately 50% at 10 mg/kg AC7700, it recovered within 8 h. In the brain, although the mean maximum reduction was 35%, the blood flow recovered to the original level within 24 h. The blood flow in the kidney cortex did not change at all. In the bone marrow, tBF decreased by approximately 80%. Generally, the blood flow reduction in normal tissues tended to be reversible. The effect on tumor growth and the histological effect were also dependent on the dose of AC7700. The tumor growth was markedly inhibited by 10 mg/ kg AC7700 and extensive necrosis was induced. Lymph node metastases were significantly inhibited and survival was prolonged significantly. In the control group, all 8 SLC tumor-bearing rats died of cancer, the presence of which was verified by gross and microscopic evaluation, within 45 days after tumor implantation. On the other hand, in the treated group, 2 of 8 rats recovered completely and survived. No obvious side effects such as body weight loss, anemia or diarrhea were observed at the dose used in this experiment. From these results, we conclude that strong antitumor effects are obtained by stopping tumor tBF irreversibly and by shutting off the nutritional supply into tumor tissue. AC7700 has been demonstrated to be a promising anticancer compound which has such an action.

Comparison of the effects of intravenously bolus-administered endothelin-1 and infused angiotensin II on the subcutaneous tumor blood flow in anesthetized rats

To evaluate the effects of endothelin-1 (ET-1) on tumor blood flow, the authors measured the mean arterial blood pressure (MABP) of enflurane-anesthetized male Donryu rats and the tissue blood flow of subcutaneously implanted tumor (Yoshida rat ascites hepatoma LY-80) by using a hydrogen clearance method. The tumor blood flow was evaluated in terms of the ratio to the maximum blood flow, which was defined as the largest flow in the same position during successive measurements. After bolus intravenous administration of ET-1 (1.0 nmol/kg), MABP reached approximately 140 mmHg (at 5-30 min), diminishing gradually to the baseline level over 2 h. The tumor blood flow increased from 36.7 +/- 20.6 to 59.5 +/- 30.2% (n = 32, P less than 0.001, at 2 min), returning to the baseline level at 10 min. On the other hand, at 2 min after the beginning of continuous intravenous infusion of [Asp1, Ile5]-angiotensin II (AII; the dose was determined by a blood pressure control system for keeping MABP at approximately 150 mmHg, consequently 0.26 micrograms/kg/min on the average), the tumor blood flow increased from 42.3 +/- 21.6 to 76.4 +/- 22.6% (n = 32, P less than 0.001), which was significantly larger than the flow after ET-1. The results indicate that hypertension induced by systemic ET-1 injection is less effective than hypertension induced by continuous systemic AII infusion in increasing tumor blood flow; AII is probably a suitable agent as a safe and effective enhancer of tumor blood flow. Moreover, ET-1 appears to constrict arterial vessels in the microcirculation time-dependently, while AII constricts probably only normal peripheral arterioles.

In vivo analysis of tumor vascularization in the rat

By using transparent chambers in rats, we have directly observed tumor-induced neovascularization in the early stage and the formation of intricate networks in Yoshida rat ascites hepatoma AH109A and Sato lung carcinoma at high magnification. We counted branching point numbers per unit area in the microvascular network with and without tumors in order to clarify the sites from which new vascular sprouts originate. Branching point number per unit area in normal tissue was 13.6 +/- 7.4/0.1 mm2 in the field near a terminal arteriole, and 12.9 +/- 7.3/0.1 mm2 in the field distant from a terminal arteriole. There was no significant difference between these two fields in the normal vascular network. On the other hand, in the tumor vascular network, the branching point number in the field near a terminal arteriole was 50.4 +/- 12.6/0.1 mm2, and 30.1 +/- 11.5/0.1 mm2 in the field distant from a terminal arteriole. The difference is highly significant (P less than 0.001). The frequency with which new capillaries originated from veins and venules was very low. We concluded from these results that the position from which tumor vessels originated was usually the terminal portion of a terminal arteriole.