Effect of continuous regional vasoactive agent infusion on liver metastasis blood flow

Nanomedicine for drug targeting: strategies beyond the enhanced permeability and retention effect

The growing research interest in nanomedicine for the treatment of cancer and inflammatory-related pathologies is yielding encouraging results. Unfortunately, enthusiasm is tempered by the limited specificity of the enhanced permeability and retention effect. Factors such as lack of cellular specificity, low vascular density, and early release of active agents prior to reaching their target contribute to the limitations of the enhanced permeability and retention effect. However, improved nanomedicine designs are creating opportunities to overcome these problems. In this review, we present examples of the advances made in this field and endeavor to highlight the potential of these emerging technologies to improve targeting of nanomedicine to specific pathological cells and tissues.

Radiotherapy combined with transarterial infusion chemotherapy and concurrent infusion of a vasoconstrictor agent for nonresectable advanced hepatic hilar duct carcinoma

BACKGROUND

The treatment of patients with advanced hepatic hilar duct carcinoma is a challenging problem. The current study was performed to evaluate the outcome of patients with advanced hepatic hilar duct carcinoma who received external beam radiotherapy (EBRT) combined with transarterial chemotherapy and infusion of a vasoconstrictor.

METHODS

Between April 1993 and December 2002, 23 patients with histopathologically confirmed hilar duct carcinoma entered the study. The median total dose of EBRT was 41.4 grays (Gy). Transarterial chemotherapy was performed twice during EBRT. It was comprised of an infusion of a cocktail of 20 mg of epirubicin, 10 mg of mitomycin C, and 500 mg of 5-fluorouracil and was administered 1 minute after injection of epinephrine via a catheter introduced in the hepatic arteries. After the combined treatment, the patients underwent biliary endoprosthesis after evaluation of the initial response to treatment by percutaneous transhepatic cholangiography (PTC). The initial responses based on PTC were classified into four categories: CR, no stenosis; PR, relief of stenosis/obstruction; NC, no change; and PD, progressive stenosis/obstruction. The outcome parameters were survival rates and time, as well as frequency and type of complications.

RESULTS

Excluding 1 patient who discontinued the treatment, the initial responses of 22 patients were 1 CR (5%), 8 PR (36%), 11 NC (50%), and 2 PD (9%). The response rate was 41%. The overall survival rates at 1 year, 2 years, and 3 years after treatment were 59%, 36%, and 18%, respectively.

CONCLUSIONS

The combination of radiotherapy, transarterial infusion chemotherapy, and concurrent infusion of a vasoconstrictor can be delivered safely with good efficacy for patients with advanced hilar duct carcinoma.

Loss of function of vascular smooth muscle cells by nitric oxide-dependent and -independent interactions with tumorigenic cells

Little is known about the interaction of tumor cells with host vascular smooth muscle cells. In reconstitution experiments, tumorigenic cell lines (including the rat hepatocarcinoma Morris 7777 and human melanoma M-21) were cultured for 17 hr in the presence of rat aortic rings, subsequently evaluated in contractility assays (response to phenylephrine and KCl). An agonist-independent loss of contractility was observed in rings pre-incubated with either tumorigenic cell lines or their conditioned medium (CM). The depressing effect of Morris cells depends largely on the expression of inducible nitric oxide synthase (iNOS) in smooth muscle cells and was reversed by an inhibitor of this enzyme; iNOS immunoreactivity was verified in some muscular vessels at the periphery of tumors formed by the Morris cell line in rats. The M-21 melanoma produces cytotoxicity in rat aortic rings (presence of single stranded DNA, cleavage of PARP, in differentiated smooth muscle only), accounting for the irreversible loss of contractility. The cytotoxicity produced by M-21 CM is not dependent on NO. Gel filtration of CM suggests that both the iNOS- and cytotoxicity-inducing substances from Morris hepatoma cells or M-21 cells, respectively, are mainly of low molecular weight (1 kDa or less). Other cell lines derived from rat or human tumors produce minimal effects on the rat aorta smooth muscle (H4-II-E-C3) or an irreversible anergy (RBL, MDA-MB-231, HEP-3B, HEP G2). The results emphasize that inhibition of vascular smooth muscle is relevant to tumor biology both by modulation of tumoral hemodynamics and by influencing the state of vessel maturation.

Continuous angiotensin II infusion increases tumour: normal blood flow ratio in colo-rectal liver metastases

Insufficient blood flow within colo-rectal hepatic metastases is a factor which may limit drug delivery to, and thus the response of, these tumours to regional chemotherapy. Loco-regional flow may be manipulated pharmacologically to enhance the tumour blood flow relative to that of the normal liver. However, as yet, only transient effects have been studied. Patients receiving regional chemotherapy for unresectable hepatic disease were given a 45 min regional infusion of the vasoconstrictor Angiotensin II. Intrahepatic blood flow distribution was assessed serially by Positron Emission Tomography (PET) imaging together with the trapping tracer copper(II) pyruvaldehyde bis(N-4-methylthiosemicarbazone) (Cu-PTSM) labelled using copper-62. Eleven lesions in nine patients were studied, with no adverse effects. Prior to Angiotensin II administration tumour blood flow was generally found to be greater than that of liver (10/11 lesions; 8/9 patients; median TNR 1.3, iqr 0.9-2.5). A significant increase in relative flow to tumour was seen in response to 10 min Angiotensin II infusion in most cases (7/11 lesions; 7/9 patients; median TNR 2.1, iqr 1.4-4.1; P = 0.008), which appeared to be sustained throughout the 45 min infusion period (median TNR 1.85, iqr 1.3-3.8; P = 0.03). These effects were accompanied by transient elevation of mean arterial pressure, but no change in pulse rate. These observations suggest that prolonged regional vasoconstrictor administration could prove useful in the management of unresectable colo-rectal hepatic metastases, and that further development of vascular manipulation to enhance tumour targeting and drug delivery is warranted.

Disparate responses of tumour vessels to angiotensin II: tumour volume-dependent effects on perfusion and oxygenation

Perfusion and oxygenation of experimental tumours were studied during angiotensin II (AT II) administration whereby the rate of the continuous AT II infusion was chosen to increase the mean arterial blood pressure (MABP) by 50-70 mmHg. In subcutaneous DS-sarcomas the red blood cell (RBC) flux was assessed using the laser Doppler technique and the mean tumour oxygen partial pressure (pO2) was measured polarographically using O2-sensitive catheter and needle electrodes. Changes in RBC flux with increasing MABP depended mainly on tumour size. In small tumours, RBC flux decreased with rising MABP whereas in larger tumours RBC flux increased parallel to the MABP. As a result of these volume-dependent effects on tumour blood flow, the impact of AT II on tumour pO2 was also mainly tumour volume-related. In small tumours oxygenation decreased with increasing MABP during AT II infusion, whereas in large tumours a positive relationship between blood pressure and O2 status was found. This disparate behaviour might be the result of the co-existence of two functionally distinct populations of tumour vessels. In small tumours, perfusion decreases presumably due to vasoconstriction of pre-existing host vessels feeding the tumour. In larger malignancies, newly formed tumour vessels predominate and seem not to have this vasoresponsive capability (lack of smooth muscle cells and/or AT receptors), resulting in an improvement of perfusion which is not tumour-related per se, but is due to the increased perfusion pressure.

Noradrenaline improves the tumour to normal blood flow ratio and drug delivery in a model of liver metastases

BACKGROUND

Vasopressors administered via the hepatic artery appear to increase drug delivery to colorectal liver metastases, but are limited by a short duration of action. This study measured their effect on blood flow and drug delivery during a prolonged infusion in a model of liver metastases.

METHODS

In Hooded Lister rats with liver metastases, blood flow in tumour and adjacent normal liver was measured using laser Doppler flowmetry during a 30-min hepatic arterial infusion of endothelin 1, angiotensin II, vasopressin, N-nitro-L-arginine methyl ester (L-NAME), noradrenaline or saline (n = 6 per group). The same agents were co-administered with radiolabelled 5-fluorouracil (5-FU) (n = 6 per group) and uptake in the tumour and normal liver was measured.

RESULTS

The mean(s.d.) duration of effect and resulting percentage changes in tumour to normal blood flow ratio of the vasopressors during this period were: noradrenaline, 2.9(0.4) min and 34(5) per cent (P < 0.05); angiotensin II, 4.2(0.2) min and 10(2) per cent (P < 0.05); vasopressin, 11.1(0.9) min and 7(2) per cent (P < 0.05); endothelin 1, 21.5(2.3) min and 14(5) per cent (P < 0.05); and L-NAME, 22.6(3.3) min and 2(1) per cent (P not significant). The mean(s.d.) uptake of radiolabelled 5-FU by the tumour in the groups studied was: saline, 5.1(3.2) x 10(5) c.p.m. per g tissue; angiotensin II, 5.1(1.4) x 10(5) c.p.m. per g; endothelin 1, 15.8(14.2) x 10(5) c.p.m. per g; L-NAME, 3.5(1.3) x 10(5) c.p.m. per g; and vasopressin, 6.8(3.5) x 10(5) c.p.m. per g. Significant improvements in 5-FU uptake only resulted from noradrenaline infusion (22.0(9.8) x 10(5) c.p.m. per g; P < 0.05).

CONCLUSION

These findings suggest that hepatic arterially infused noradrenaline might be used to improve drug delivery to liver metastases.