Period prevalence of uveitis in human T-lymphotropic virus 1 carriers versus noncarriers in a highly endemic area: The Nagasaki Islands Study.

The magnitude of the effect of human T-lymphotropic virus 1 (HTLV-1) infection on uveitis remains unclear. We conducted a cross-sectional study in a highly endemic area of HTLV-1 in Japan. The study included 4265 residents (men, 39.2%), mostly middle-aged and older individuals with a mean age of 69.9 years, who participated in our surveys between April 2016 and September 2022. We identified HTLV-1 carriers by screening using chemiluminescent enzyme immunoassays and confirmatory tests, and the proportion of carriers was 16.1%. Participants with uveitis were determined from the medical records of all hospitals and clinics where certified ophthalmologists practiced. We conducted logistic regression analyses in an age- and sex-adjusted model to compute the odds ratio (OR) and 95% confidence interval (CI) of uveitis according to HTLV-1 infection status. Thirty-two (0.8%) participants had uveitis. For HTLV-1 carriers, the age- and sex-adjusted OR (95% CI) of uveitis was 3.27 (1.57-6.72) compared with noncarriers. In conclusion, HTLV-1 infection was associated with a higher risk of uveitis among mostly middle-aged and older Japanese residents in a highly endemic HTLV-1 area. Our findings suggest that physicians who treat HTLV-1 carriers should assess ocular symptoms, and those who diagnose patients with uveitis should consider HTLV-1 infection.

The Challenge to Deliver Oxaliplatin (l-OHP) to Solid Tumors: Development of Liposomal l-OHP Formulations.

Oxaliplatin (l-OHP) is a third-generation platinum (Pt) agent approved for the treatment of patients with advanced colorectal cancer. Despite the fact that l-OHP has shown clinical therapeutic efficacy and better tolerability compared with other Pt agents, the use of l-OHP has been limited to clinical settings because of dose-limiting side effects such as cumulative neurotoxicity and acute dysesthesias, which can be severe. In preclinical and clinical studies, our group and several others have attempted the delivery of l-OHP to solid tumors via encapsulation in PEGylated liposomes. Herein, we review these attempts.

Liposomalization of Oxaliplatin Exacerbates the Non-Liposomal Formulation-Induced Decrease of Sweet Taste Sensitivity in Rats.

Here, we investigated whether or not the characteristics of the oxaliplatin-induced sweet taste sensitivity were altered by PEGylated liposomalization of oxaliplatin (liposomal oxaliplatin), which enhances its anticancer efficacy. Liposomal oxaliplatin and oxaliplatin were intravenously and intraperitoneally, respectively, administered to male Sprague-Dawley rats at the total dose of 8 mg/kg. A brief-access test for evaluation of sweet taste sensitivity on day 7 revealed that both liposomal oxaliplatin and oxaliplatin decreased the sensitivity of rats, the degree with the former being greater than in the case of the latter. Liposomalization of oxaliplatin increased the accumulation of platinum in lingual non-epithelial tissues, through which taste nerves passed. The lingual platinum accumulation induced by not only liposomal oxaliplatin but also oxaliplatin was decreased on cooling of the tongue during the administration. In the current study, we revealed that liposomalization of oxaliplatin exacerbated the oxaliplatin-induced decrease of sweet taste sensitivity by increasing the accumulation of platinum/oxaliplatin in lingual non-epithelial tissues. These findings may suggest that reduction of liposomal oxaliplatin distribution to the tongue on cooling during the administration prevents exacerbation of the decrease of sweet taste sensitivity, maintaining the quality of life and chemotherapeutic outcome in patients.

Long-term storage of PEGylated liposomal oxaliplatin with improved stability and long circulation times in vivo.

Liposomal anticancer drugs have been developed with improved clinical effects and reduced side effects. We have developed a PEGylated liposomal formulation of oxaliplatin that has anticancer effects in animal models of colorectal cancer with a favorable toxicity profile. To move this formulation into clinical development, a formulation that is stable during long term storage is needed, which has similar pharmacokinetics and therapeutic activity against solid tumors to the original formulation. In this study, we found that PEGylated liposomal oxaliplatin showed no changes in particle size after long term storage (12 months at 2-8 °C), but phospholipid degradation had occurred. Hence, the stored formulation had compromised membrane integrity, resulting in decreased in vivo circulation times of the liposomes. To improve the stability during long-term storage, a screening study to obtain an appropriate stabilizer was carried out. The buffer 2-morpholinoethansulfonic acid (MES) attenuated not only phospholipid degradation but also oxaliplatin degradation, unlike most other excipients. After 12 months storage at 2-8 °C in the presence of MES only slight degradation of phospholipids in PEGylated liposomal oxaliplatin occurred, resulting in similar in vivo pharmacokinetic profiles of the encapsulated oxaliplatin to the original formulation. Long term stability of PEGylated liposomal oxaliplatin was achieved by addition of MES, resulting in long circulation half-lives in vivo, a property which would be expected to lead to increased suppression of tumor growth and reduced side effects. Our formulation may now be suitable for clinical development.

Intratumoral Visualization of Oxaliplatin within a Liposomal Formulation Using X-ray Fluorescence Spectrometry.

Microsynchrotron radiation X-ray fluorescence spectrometry (µ-SR-XRF) is an X-ray procedure that utilizes synchrotron radiation as an excitation source. µ-SR-XRF is a rapid, nondestructive technique that allows mapping and quantification of metals and biologically important elements in cell or tissue samples. Generally, the intratumor distribution of nanocarrier-based therapeutics is assessed by tracing the distribution of a labeled nanocarrier within tumor tissue, rather than by tracing the encapsulated drug. Instead of targeting the delivery vehicle, we employed µ-SR-XRF to visualize the intratumoral microdistribution of oxaliplatin (l-OHP) encapsulated within PEGylated liposomes. Tumor-bearing mice were intravenously injected with either l-OHP-containing PEGylated liposomes (l-OHP liposomes) or free l-OHP. The intratumor distribution of l-OHP within tumor sections was determined by detecting the fluorescence of platinum atoms, which are the main elemental components of l-OHP. The l-OHP in the liposomal formulation was localized near the tumor vessels and accumulated in tumors at concentrations greater than those seen with the free form, which is consistent with the results of our previous study that focused on fluorescent labeling of PEGylated liposomes. In addition, repeated administration of l-OHP liposomes substantially enhanced the tumor accumulation and/or intratumor distribution of a subsequent dose of l-OHP liposomes, presumably via improvements in tumor vascular permeability, which is also consistent with our previous results. In conclusion, µ-SR-XRF imaging efficiently and directly traced the intratumor distribution of the active pharmaceutical ingredient l-OHP encapsulated in liposomes within tumor tissue. µ-SR-XRF imaging could be a powerful means for estimating tissue distribution and even predicting the pharmacological effect of nanocarrier-based anticancer metal compounds.

Liposomalization of oxaliplatin induces skin accumulation of it, but negligible skin toxicity.

Liposomalization causes alteration of the pharmacokinetics of encapsulated drugs, and allows delivery to tumor tissues through passive targeting via an enhanced permeation and retention (EPR) effect. PEGylated liposomal doxorubicin (Doxil®, Lipo-DXR), a representative liposomal drug, is well-known to reduce cardiotoxicity and increase the anti-tumor activity of DXR, but to induce the hand-foot syndrome (HFS) as a result of skin DXR accumulation, which is one of its severe adverse effects. We have developed a new liposomal preparation of oxaliplatin (l-OHP), an important anti-tumor drug for treatment of colorectal cancer, using PEGylated liposomes (Lipo-l-OHP), and showed that Lipo-l-OHP exhibits increased anti-tumor activity in tumor-bearing mice compared to the original preparation of l-OHP. However, whether Lipo-l-OHP causes HFS-like skin toxicity similar to Lipo-DXR remains to be determined. Administration of Lipo-l-OHP promoted accumulation of platinum in rat hind paws, however, it caused negligible morphological and histological alterations on the plantar surface of the paws. Administration of DiI-labeled empty PEGylated liposomes gave almost the same distribution profile of dyes into the dermis of hind paws with DXR as in the case of Lipo-DXR. Treatment with Lipo-l-OHP, Lipo-DXR, DiI-labeled empty PEGylated liposomes or empty PEGylated liposomes caused migration of CD68+ macrophages into the dermis of hind paws. These findings suggest that the skin toxicity on administration of liposomalized drugs is reflected in the proinflammatory characteristics of encapsulated drugs, and indicate that Lipo-l-OHP with a higher anti-cancer effect and no HFS may be an outstanding l-OHP preparation leading to an improved quality of life of cancer patients.

Modulation of antitumor immunity contributes to the enhanced therapeutic efficacy of liposomal oxaliplatin in mouse model.

Immune modulation of the tumor microenvironment has been reported to participate in the therapeutic efficacy of many chemotherapeutic agents. Recently, we reported that liposomal encapsulation of oxaliplatin (l-OHP) within PEGylated liposomes conferred a superior antitumor efficacy to free l-OHP in murine colorectal carcinoma-bearing mice through permitting preferential accumulation of the encapsulated drug within tumor tissue. However, the contribution of the immune-modulatory properties of liposomal l-OHP and/or free l-OHP to the overall antitumor efficacy was not elucidated. In the present study, therefore, we investigated the effect of liposomal encapsulation of l-OHP within PEGylated liposomes on the antitumor immunity in both immunocompetent and immunodeficient mice. Liposomal l-OHP significantly suppressed the growth of tumors implanted in immunocompetent mice, but not in immunodeficient mice. In immunocompetent mice, liposomal l-OHP increased the tumor MHC-1 level and preserved antitumor immunity through decreasing the number of immune suppressor cells, including regulatory T cells, myeloid-derived suppressor cells, and tumor-associated macrophages, which collectively suppress CD8+ T cell-mediated tumor cells killing. In contrast, free l-OHP ruined antitumor immunity. These results suggest that the antitumor efficacy of liposomal l-OHP is attributed, on the one hand, to its immunomodulatory effect on tumor immune microenvironment that is superior to that of free l-OHP, and on the other hand, to its direct cytotoxic effect on tumor cells.

Improvement of intratumor microdistribution of PEGylated liposome via tumor priming by metronomic S-1 dosing.

The efficient delivery of nanocarrier-based cancer therapeutics into tumor tissue is problematic. Structural abnormalities, tumor vasculature heterogeneity, and elevated intratumor pressure impose barriers against the preferential accumulation of nanocarrier-based cancer therapeutics within tumor tissues and, consequently, compromise their therapeutic efficacy. Recently, we have reported that metronomic S-1, orally available tegafur formulation, dosing synergistically augmented the therapeutic efficacy of oxaliplatin (l-OHP)-containing PEGylated liposome without increasing the toxicity in animal model. However, the exact mechanism behind such synergistic effect was not fully elucidated. In this study, therefore, we tried to shed the light on the contributions of metronomic S-1 dosing to the enhanced accumulation and/or spatial distribution of PEGylated liposome within tumor tissue. Tumor priming with metronomic S-1 treatment induced a potent apoptotic response against both angiogenic endothelial cells and tumor cells adjacent to tumor blood vessels, resulting in enhanced tumor blood flow via transient normalization of tumor vasculature, along with alleviation of intratumor pressure. Such a change in the tumor microenvironment imparted by S-1 treatment allows efficient delivery of PEGylated liposome to tumor tissue and permits their deep penetration/distribution into the tumor mass. Such a priming effect of S-1 dosing can be exploited as a promising strategy to enhance the therapeutic efficacy of nanocarrier-based cancer therapeutics suffering from inadequate/heterogeneous delivery to tumor tissues.

Sequential treatment of oxaliplatin-containing PEGylated liposome together with S-1 improves intratumor distribution of subsequent doses of oxaliplatin-containing PEGylated liposome.

We recently reported that combination therapy with metronomic S-1 dosing and oxaliplatin (l-OHP)-containing PEGylated liposomes improved antitumor activity in a murine colorectal tumor model. However, little is known about the mechanism underlying such improved therapeutic efficacy. Here we investigated the impact of combined treatment on biodistribution, tumor accumulation and intratumor distribution of test PEGylated liposomes and on the structure of tumor vasculature in a solid tumor. The combined treatment clearly enhanced tumor accumulation and intratumor distribution of a subsequent test dose of PEGylated liposome as a result of on the one hand prolonging blood circulation of test liposome and on the other hand the alteration in tumor microenvironment. The l-OHP-containing PEGylated liposomes contributed predominantly to the enhanced tumor accumulation and altered tumor distribution of test liposome. On the other hand, metronomic S-1 dosing contributed to the altered tumor distribution but not the tumor accumulation of test liposome. The antitumor effect of the combined treatment, reflected by the proportion of apoptotic cells in the tumor, was approximately equally accounted for by each of the two treatments, leading to a roughly additive effect. In conclusion, 1-OHP-containing PEGylated liposome together with S-1 enhanced intratumor influx, leading to improved antitumor activity of subsequently injected 1-OHP-containing PEGylated liposomes and/or S-1. This strategy we propose, which is clinically applicable, may overcome the problems related to the use of EPR effect-based nanocarrier systems.

Tumor-type-dependent vascular permeability constitutes a potential impediment to the therapeutic efficacy of liposomal oxaliplatin.

The delivery of anticancer agents to solid tumors is problematic. Nanomolecular drug carriers represent an attractive alternative strategy for efficient anticancer drug delivery to tumor tissue, because they appear to target tumors and have limited toxicity in normal tissue. However, inadequate and heterogeneous distribution of nanocarriers in tumor tissue is a major impediment for their efficient use in clinical cancer therapy. In the present study, we examined the effect of tumor type on the intratumor accumulation and distribution of polyethylene glycol (PEG)-coated liposomes using in vivo mouse models of three cancer cell lines: colon adenocarcinoma (C26), Lewis lung carcinoma (LLC), and B16BL6 melanoma (B16BL6). The tumor growth inhibition and the apoptotic response of oxaliplatin (l-OHP) encapsulated in the PEG-coated liposomes were tumor type dependent and correlated with a tendency toward tumor accumulation and intratumor distribution of PEG-coated liposome, in contrast to in vitro cytotoxicity of l-OHP. A potent antitumor effect observed in both C26 and LLC tumor-bearing mice was attributed to the enhanced extravasation with subsequent preferential accumulation of PEG-coated liposomes through tumor vasculature with high permeability. Our results suggest that the permeability of tumor vasculature constitutes a potential impediment to tumor localization and thereby to the antitumor efficacy of PEG-coated liposomal anticancer drugs.

Combination therapy with metronomic S-1 dosing and oxaliplatin-containing PEG-coated cationic liposomes in a murine colorectal tumor model: synergy or antagonism?

Combination therapy with 2 or more drugs with different mechanisms of action has been considered a promising strategy for the effective treatment of advanced and metastatic cancers. However, the rational design of combination therapy represents a potential prerequisite for its effectiveness. Recently, we showed that the combination of oral metronomic S-1 dosing with oxaliplatin (l-OHP)-containing PEG-coated "neutral" liposomes exerted excellent antitumor activity. In addition, we recently designed a PEG-coated "cationic" liposome for dual-targeting delivery of l-OHP to tumor endothelial cells and tumor cells in a solid tumor. This targeted liposomal l-OHP formulation showed efficient antitumor activity in a murine tumor model, compared with l-OHP-containing PEG-coated "neutral" liposomes. In the present study, we investigated the issue of whether metronomic S-1 dosing with l-OHP-containing PEG-coated "cationic" liposomes creates synergy. Unfortunately, metronomic S-1 dosing resulted in impaired delivery of PEG-coated "cationic" liposomes into tumor tissue, presumably by decreasing the binding sites on tumor blood vessels available for the liposomes. The anticipated cytotoxic synergistic effect of the combination treatment was not achieved. Instead, the combination treatment showed lower antitumor efficacy than l-OHP-containing PEG-coated "cationic" liposomes alone. These results suggest that the combined treatment of S-1 and l-OHP-containing PEG-coated "cationic" liposomes seems to be antagonistic rather than synergistic.

Improved intratumoral delivery of PEG-coated siRNA-lipoplexes by combination with metronomic S-1 dosing in a murine solid tumor model.

Efficient systemic siRNA delivery to cells in the target tissue is a current critical challenge in the drug delivery field. Several studies have demonstrated that nanoparticles such as polyethylene glycol (PEG)-coated siRNA-lipoplexes may enhance the systemic delivery of siRNA to tumor. However, the disordered tumor microenvironment still poses a potential impediment with respect to the efficient delivery of PEG-coated siRNA-lipoplexes. Recently, we showed that metronomic S-1 dosing (daily oral administration) enhanced the accumulation of PEG-coated siBcl-2-lipoplex in DLD-1 solid tumor mouse model. In this study, to extend our work, we investigated the effect of metronomic S-1 dosing on the intratumoral accumulation and, thereby, therapeutic efficacy of PEG-coated siAgo2-lipoplex in Lewis lung carcinoma cells (LLCC) solid tumor mouse model. Also, we tried to elucidate the probable mechanism of the enhanced intratumoral accumulation of PEG-coated siRNA-lipoplexes induced by S-1 combination therapy. Results showed that metronomic S-1 dosing improved systemic delivery of intravenously injected PEG-coated siAgo2-lipoplexes into a LLCC solid tumor. In addition, the combined therapy of S-1 and PEG-coated siRNA-lipoplexes resulted in potent tumor growth suppression. These findings offer proof-of-concept for the improved systemic delivery of PEG-coated siRNA-lipoplexes by metronomic S-1 dosing in whatever tumor model used, and this may pose a promising therapeutic strategy to conquer cancer progression.

A double-modulation strategy in cancer treatment with a chemotherapeutic agent and siRNA.

5-Fluorouracil (5-FU) is broadly considered the drug of choice for treating human colorectal cancer (CRC). However, 5-FU resistance, mainly caused by the overexpression of antiapoptotic proteins such as Bcl-2, often leads ultimately to treatment failure. We here investigated the effect of Bcl-2 gene silencing, using small interfering RNA (siRNA) (siBcl-2), on the efficacy of 5-FU in CRC. Transfection of siBcl-2 by a Lipofectamine2000/siRNA lipoplex effectively downregulated Bcl-2 expression in the DLD-1 cell line (a CRC), resulting in significant cell growth inhibition in vitro upon treatment with 5-FU. For in vivo treatments, S-1, an oral formulation of Tegafur (TF), a prodrug of 5-FU, was used to mimic 5-FU infusion. The combined treatment of polyethylene glycol (PEG)-coated siBcl-2-lipoplex and S-1 showed superior tumor growth suppression in a DLD-1 xenograft model, compared to each single treatment. Surprisingly, daily S-1 treatment enhanced the accumulation of PEG-coated siBcl-2-lipoplex in tumor tissue. We propose a novel double modulation strategy in cancer treatment, in which chemotherapy enhances intratumoral siRNA delivery and the delivered siRNA enhances the chemosensitivity of tumors. Combination of siRNA-containing nanocarriers with chemotherapy may compensate for the limited delivery of siRNA to tumor tissue. In addition, such modulation strategy may be considered a promising therapeutic approach to successfully managing 5-FU-resistant tumors.

Immunoliposomal drug-delivery system targeting lectin-like oxidized low-density lipoprotein receptor-1 for carotid plaque lesions in rats.

OBJECT: Targeted drug delivery with immunoliposomes has been applied to various in vivo animal models and is newly focused as a novel therapeutic target. Lectin-like oxidized low-density lipoprotein receptor-1 (LOX1) is a potent regulator of systemic atherosclerosis, and the authors focused on its effect on carotid plaques. The authors developed a LOX1-targeted liposomal rho-kinase inhibitor and examined the therapeutic effect on carotid intimal hypertrophy in rats. METHODS: LOX1-targeted rho-kinase inhibitor fasudil-containing liposomes, composed of hydrogenated soy phosphatidylcholine/cholesterol/PEG(2000)-DSPE, were prepared by conjugating anti-LOX1 antibodies on the surface and by remote loading of fasudil. Carotid intimal hypertrophy was induced by balloon injury, and the drugs were intravenously administered on Day 3 postinjury. The rats were divided into 4 groups: nontreatment, treatment with intravenous fasudil (2 mg), treatment with liposomal fasudil (2 mg), and treatment with LOX1-targeted liposomal fasudil (2 mg). The authors compared intimal hypertrophy, atherosclerotic factor, and matrix metalloproteinase-9 expression among groups. RESULTS: DiI-labeled LOX1-targeted liposomes were prominently observed in the lesions on Day 7 after the surgery. The intimal thickness was significantly reduced in the LOX1-targeted liposomal fasudil-treated group (mean 81.6 ± 13.9 µm) compared with the other groups (no treatment 105.4 ± 16.8 µm; fasudil treatment 102.4 ± 20.0 µm; and liposomal fasudil treatment 102.8 ± 22.2 µm; p = 0.046). Matrix metalloproteinase-9 expression was also significantly reduced in the LOX1-targeted liposomal fasudil group. CONCLUSIONS: Liposomes conjugated with anti-LOX1 antibody effectively reached carotid artery lesions, and liposomal rho-kinase significantly inhibited intimal hypertrophy. The new liposomal drug delivery system targeting LOX1 may become a therapeutic strategy for atherosclerotic diseases.

Combination therapy of metronomic S-1 dosing with oxaliplatin-containing polyethylene glycol-coated liposome improves antitumor activity in a murine colorectal tumor model.

Metronomic chemotherapy has been advocated recently as a novel chemotherapeutic regimen. Polyethylene glycol (PEG)-coated liposomes are well known to accumulate in solid tumors by virtue of the highly permeable angiogenic blood vessels characteristic for growing tumor tissue, the so-called "enhanced permeability and retention (EPR) effect". To expand the range of applications and investigate the clinical value of the combination strategy, the therapeutic benefit of metronomic S-1 dosing in combination with oxaliplatin (l-OHP)-containing PEG-coated liposomes was evaluated in a murine colon carcinoma-bearing mice model. S-1 is an oral fluoropyrimidine formulation and metronomic S-1 dosing is a promising alternative to infused 5-FU in colorectal cancer therapy. Therefore, the combination of S-1 with l-OHP may be an alternative to FOLFOX (infusional 5-FU/leucovorin (LV) in combination with l-OHP), which is a first-line therapeutic regimen of a colorectal carcinoma. The combination of oral metronomic S-1 dosing with intravenous administration of liposomal l-OHP formulation exerted excellent antitumor activity without severe overlapping side-effects, compared with either metronomic S-1 dosing, free l-OHP or liposomal l-OHP formulation alone or metronomic S-1 dosing plus free l-OHP. We confirmed that the synergistic antitumor effect is due to prolonged retention of l-OHP in the tumor on account of the PEG-coated liposomes, presumably via alteration of the tumor microenvironment caused by the metronomic S-1 treatment. The combination regimen proposed here may be a breakthrough in treatment of intractable solid tumors and an alternative to FOLFOX in advanced colorectal cancer therapy with acceptable tolerance and preservation of quality of life (QOL).

Sequential administration with oxaliplatin-containing PEG-coated cationic liposomes promotes a significant delivery of subsequent dose into murine solid tumor.

Recently, we designed a PEG-coated cationic liposome to achieve dual targeting delivery of l-OHP to both tumor endothelial cells and tumor cells in a solid tumor. The targeted liposomal l-OHP formulation showed an efficient antitumor activity in a murine tumor model after three sequential liposomal l-OHP injections. This led us to assume that prior dosing with liposomes might enhance the intra-tumoral accumulation of a subsequent dose, and hence improve the therapeutic efficacy of entrapped l-OHP. The present study shows that while a single liposomal l-OHP injection does not enhance tumor accumulation of subsequent test-PEG-coated cationic liposomes, two sequential injections of liposomal l-OHP do. Cumulative cytotoxic effects of l-OHP delivered by PEG-coated cationic liposomes led to deep diffusion of a subsequent dose of liposomal l-OHP in solid tumor presumably as a result of the enlarged intra-tumoral interstitial space. Our study suggests that sequential injections of a targeted liposomal anticancer drug is of significant clinical and practical importance in enhancing the delivery of adequate quantities of anticancer agents into intractable solid tumors, and thereby may achieve a significant anticancer efficacy.

Oxaliplatin encapsulated in PEG-coated cationic liposomes induces significant tumor growth suppression via a dual-targeting approach in a murine solid tumor model.

We recently designed a PEG-coated cationic liposome targeted to angiogenic vessels and showed, in a murine dorsal air sac model, potent anti-angiogenic activity of an oxaliplatin (l-OHP) formulation of this liposome. In the present study, we extended the l-OHP formulation to a murine tumor-xenograft model. Following three injections, l-OHP containing PEG-coated cationic liposomes showed substantial tumor growth suppression and increased survival time of tumor-bearing mice without apparent side effects, compared with other l-OHP containing PEG-coated neutral liposomes and free l-OHP. In vivo imaging showed a preferential tumor accumulation and a broader distribution of PEG-coated cationic liposomes, compared with PEG-coated neutral liposomes. In addition, PEG-coated cationic liposomes delivered larger amounts of l-OHP into the tumor tissue than other l-OHP formulations, correlating with its antitumor efficiency. In vitro studies indicated that PEG-coated cationic liposomes were internalized not only by tumor cells but also by endothelial cells, and consequently its l-OHP formulation displayed higher cytotoxicity towards both cell types as compared with l-OHP containing PEG-coated neutral liposomes. In summary, l-OHP containing PEG-coated cationic liposomes induced significant tumor growth suppression, presumably by delivering encapsulated l-OHP into both tumor endothelial cells and tumor cells. Such dual targeting approach, i.e. vascular-targeting and tumor-targeting with a single liposomal l-OHP formulation, may have great potential for overcoming some major limitations in conventional chemotherapy.

Oxaliplatin targeting to angiogenic vessels by PEGylated cationic liposomes suppresses the angiogenesis in a dorsal air sac mouse model.

Oxaliplatin (trans-l-diaminocyclohexane oxalatoplatinum, l-OHP) is a third-generation platinum analogue with proven anti-tumor activity against many tumor cell lines, however it does not show sufficient anti-tumor activity in vivo when used alone. In order to overcome this problem and to achieve an anti-angiogenic therapy with l-OHP, the drug was encapsulated into PEG-coated cationic liposomes, which were designed to target the newly formed vessels, and its anti-angiogenic activity was evaluated in an in vivo mouse dorsal air sac (DAS) assay. For the DAS assay, chambers filled with tumor cells were implanted underneath the dorsal skin. l-OHP encapsulated in PEG-coated cationic liposomes (5 mg/kg mice) was intravenously injected once on day 1, 2, 3 or 4 after chamber implantation. On the fifth day after chamber implantation, animals were sacrificed and tumor-angiogenesis was evaluated. Liposome-encapsulated l-OHP completely suppressed angiogenesis in the skin when it was administered day 3 after chamber implantation. Under similar experimental conditions, neither l-OHP encapsulated in PEG-coated neutral liposomes, nor free l-OHP, nor "empty" (no drug containing) PEG-coated cationic liposomes showed such strong suppressive effect. The present study suggests that the liposomal formulation of l-OHP, which targeted to angiogenic vessels, has a remarkable in vivo anti-angiogenic activity and the formulation may become a promising novel approach to achieve anti-angiogenic therapy.

Quantitative analysis of isolated and clustered DNA damage induced by gamma-rays, carbon ion beams, and iron ion beams.

Ionizing radiation induces multiple damaged sites (clustered damage) together with isolated lesions in DNA. Clustered damage consists of closely spaced lesions within a few helical turns of DNA and is considered to be crucial for understanding the biological consequences of ionizing radiation. In the present study, two types of DNA, supercoiled plasmid DNA and linear lambda DNA, were irradiated with gamma-rays, carbon ion beams, and iron ion beams, and the spectra and yield of isolated DNA damage and bistranded clustered DNA damage were fully analyzed. Despite using different methods for damage analysis, the experiments with plasmid and lambda DNA gave largely consistent results. The spectra of both isolated and clustered damage were essentially independent of the quality of the ionizing radiation used for irradiation. The yields of clustered damage as well as of isolated damage decreased with the different radiation beams in the order gamma> C > Fe, thus exhibiting an inverse correlation with LET [gamma (0.2 keV/microm) < C (13 keV/microm) < Fe (200 keV/microm)]. Consistent with in vitro data, the yield of chromosomal DNA DSBs decreased with increasing LET in Chinese hamster cells irradiated with carbon ion beams with different LETs, suggesting that the decrease in the yield of clustered damage with increasing LET is not peculiar to in vitro irradiation of DNA, but is common for both in vitro and in vivo irradiation. These results suggest that the adverse biological effect of the ionizing radiation is not simply accounted for by the yield of clustered DNA damage, and that the complexity of the clustered damage needs to be considered to understand the biological consequences of ionizing radiation.