Intracellular targeting therapy of cisplatin-encapsulated transferrin-polyethylene glycol liposome on peritoneal dissemination of gastric cancer

Peritoneal dissemination in gastric cancer is a common fatal clinical condition with few effective therapies available. We studied the therapeutic effect of a tumor-targeting drug delivery system that uses cisplatin-encapsulated and Tf-conjugated PEG liposomes (Tf-PEG liposomes) in nude mice with peritoneal dissemination of human gastric cancer cells. Small unilamellar Tf-PEG, PEG or DSPC/CH liposomes (bare liposomes) encapsulating cisplatin were prepared by reverse-phase evaporation followed by extrusion. Electron microscopic studies revealed that Tf-PEG liposomes were internalized into tumor cells by receptor-mediated endocytosis. To examine the biodistribution of each liposome and cisplatin level, nude mice were inoculated i.p. with 10(7) MKN45P human gastric tumor cells. On the fourth day after tumor inoculation, (3)H-CHE-labeled and cisplatin-encapsulated Tf-PEG, PEG or bare liposome were inoculated i.p. The Tf-PEG liposome-administered group maintained high liposome and cisplatin levels in ascites and showed a prolonged residence time in the peripheral circulation. Uptake of Tf-PEG liposomes into the liver and spleen was significantly lower than that of bare liposomes. Uptake of Tf-PEG liposomes in disseminated tumor cells of ascites and the greater omentum was significantly higher than that of PEG or bare liposomes and a significant increase in cisplatin levels was observed in these tumor cells. Mice receiving Tf-PEG liposomes 1 and 4 days after the day of tumor inoculation showed significantly higher survival rates compared with those receiving PEG liposomes without Tf, bare liposomes or free cisplatin solution. These results suggest that cisplatin-encapsulated Tf-PEG liposomes may be useful as a new intracellular targeting carrier for treatment of gastric cancer with peritoneal dissemination.     

Pharmacokinetics of S-1 in patients with peritoneal dissemination of gastric cancer

The response of gastric cancer with peritoneal dissemination to systemic chemotherapy may be negatively affected by poor drug delivery due to the blood-peritoneal barrier. However, S-1 has been reported to be effective. We examined the pharmacokinetics of S-1 in 14 patients who had gastric cancer with peritoneal dissemination. S-1 was given from the morning of the day before surgery to the morning of surgery. Concentrations of 5-fluorouracil (5-FU) and gimeracil (CDHP) were measured in the serum, ascites, disseminated peritoneal nodes, and normal peritoneum. There was a strong correlation between 5-FU and CDHP concentrations in peritoneal tissues. The concentrations of 5-FU and CDHP in the serum were similar to those in ascites. The concentration of 5-FU was significantly higher in disseminated nodes than in the normal peritoneum. After administration of S-1 to gastric cancer patients with peritoneal dissemination, 5-FU and CDHP in the serum linearly pass through the peritoneum and enter the ascites. High concentrations of 5-FU selectively penetrate disseminated peritoneal cells.     

Pharmacodynamic behavior of liposomal antisense oligonucleotides targeting Her-2/neu and vascular endothelial growth factor in an ascitic MDA435/LCC6 human breast cancer model

The nature of anti-cancer therapeutics is currently undergoing a paradigm change, with biologic agents slowly being introduced into the therapeutic armory, displacing or complimenting the traditionally used cytotoxic agents. These new agents include monoclonal antibodies, recombinant DNA, antisense oligonucleotides (ASO) and others. To assess the new therapeutics, new predictive models are required. Utilizing the MDA435/LCC6 human breast cancer xenograft model, the pharmacokinetic behavior of antisense oligonucleotides targeted against vascular endothelial growth factor and HER-2/neu was assessed. For pharmacodynamic analysis, ASO in buffer or encapsulated in a liposomal formulation were injected intravenously or intraperitoneally into MDA435/LCC6 ascites tumor-bearing mice. Plasma antisense elimination, tissue distribution, total peritoneal antisense and peritoneal cell associated antisense levels were determined. Liposomal encapsulation led to significant decreases in the plasma elimination rate, as evidenced by an approximate 10-fold increase in mean AUC over 24 hours, as well as enhanced peritoneal cell delivery in mice bearing ascites tumors. Tissue distribution studies of both free and liposome encapsulated ASO indicated that ASO distribution was dictated primarily by the liposomal carrier when administered in liposomal form.     

Gemcitabine suppresses malignant ascites of human pancreatic cancer: correlation with VEGF expression in ascites

It has been reported that vascular endothelial growth factor (VEGF) is a potent angiogenic factor that also has the ability to increase vascular permeability. VEGF plays an important role in the development of malignant ascites in various cancers. Gemcitabine has been prescribed for patients with inoperable human pancreatic ductal carcinoma as a first-line chemotherapy. However, the response rates of patients with malignant ascites who were undergoing systemic chemotherapy were extremely limited. In the present study, we investigated the role of VEGF and the effects of gemcitabine on malignant ascites of human pancreatic ductal carcinoma. As an in vitro assay, the human pancreatic cancer cell line (SUIT-2) was incubated in DMEM supplemented with serially diluted concentrations of gemcitabine for 24 h. The expression levels of VEGF in culture media were assayed using an enzyme-linked immunosorbent assay (ELISA). As an in vivo assay, a cell suspension (1 x 10(7) cells in 100 microliters PBS) was injected into the intraperitoneal region. The mice were randomly divided into two groups (control and treated with gemcitabine). The mice were sacrificed four weeks after inoculation, the ascites volume was measured, and the extent of peritoneal dissemination was examined. The expression levels of VEGF and CD31 in peritoneal nodules were examined by immunohistochemistry. In addition, secreted VEGF protein levels were quantified using ELISA. The results show that VEGF levels in the culture medium decreased in response to gemcitabine in a dose-dependent manner. The ascites formation and peritoneal dissemination within mice were suppressed by the treatment with gemcitabine. Immunohistochemical analysis suggested that expression of VEGF and CD31 in peritoneal nodules was suppressed by gemcitabine treatment, and the VEGF protein level in ascites was significantly decreased by gemcitabine (p<0.05). These results suggest that gemcitabine controls malignant ascites and peritoneal dissemination, either directly or indirectly, via VEGF. Moreover, intraperitoneal administration of gemcitabine may be a useful therapeutic approach for patients with malignant ascites in pancreatic carcinoma.     

A case of unresectable advanced pancreatic cancer with peritoneal dissemination responding to continuous dose S-1 monotherapy after chemo-radiation therapy

A 57-year-old woman with a pancreatic body tumor was admitted to our hospital. She was diagnosed with unresectable advanced pancreatic cancer (stage IVb) due to portal vein invasion, arterial invasion, retro peritoneal invasion and lymphnode metastases, so radiation therapy (50 Gy/25 Fr) with concurrent arterial infusion of gemcitabine (GEM) was carried out. After the chemo-radiation therapy, her arterial infusion treatment of GEM was continued in our outpatient clinic for 3 months until she was complicated with ascites due to peritoneal dissemination. Peritonitis carcinomatosa was controlled by S-1 oral administration with intraperitoneal infusion of MMC and CDDP. For 18 months after discharge, she has maintained good quality of life without any adverse effects by a continuous dose of S-1 at our outpatient clinic.     

Establishment and characterization of a new cell line (SKS) from neuroendocrine small cell carcinoma of the uterine cervix and its chemosensitivity.

A new cell line (SKS) established from ascites of a patient with neuroendocrine small cell carcinoma of the uterine cervix had a good tumorigenicity and caused marked peritoneal dissemination, and was also highly sensitive to gemcitabine in an in vitro chemosensitivity test. SKS cells were small round cells with a high nuclear/cytoplasmic (N/C) ratio and grew into colony-like aggregates, forming spherical aggregates of floating cells. The population doubling time was 44 h. The number of chromosomes ranged from 50 to 56. On examination of the ultrastructure, membrane-bound dense-core neurosecretory-type granules were observed in the cytoplasm. Neuron-specific enolase (NSE) was immunocytochemically positive in the cytoplasm, and 9.3 ng/ml of NSE was detected in the cell culture supernatant. Human papillomavirus was not detected. In the p53 gene, a 3-bp deletion, AAC (Asn), was detected at codon 131 in exon 5. SKS exhibited good tumorigenicity, and the tumor doubling time was 11 days. Intraperitoneal injection of the cells caused peritoneal dissemination, and marked ascites formation was observed. SKS was highly sensitive to gemcitabine, and the 50% growth inhibitory concentration was 30 nM. SKS cells are useful as a model of neuroendocrine small cell carcinoma of the cervix, and chemotherapy using gemcitabine may possibly be effective in this malignancy.     

Antitumor effect of nuclear factor‐κB decoy transfer by mannose‐modified bubble lipoplex into macrophages in mouse malignant ascites

Patients with malignant ascites (MAs) display several symptoms, such as dyspnea, nausea, pain, and abdominal tenderness, resulting in a significant reduction in their quality of life. Tumor‐associated macrophages (TAMs) play a crucial role in MA progression. Because TAMs have a tumor‐promoting M2 phenotype, conversion of the M2 phenotypic function of TAMs would be promising for MA treatment. Nuclear factor‐κB (NF‐κB) is a master regulator of macrophage polarization. Here, we developed targeted transfer of a NF‐κB decoy into TAMs by ultrasound (US)‐responsive, mannose‐modified liposome/NF‐κB decoy complexes (Man‐PEG bubble lipoplexes) in a mouse peritoneal dissemination model of Ehrlich ascites carcinoma. In addition, we investigated the effects of NF‐κB decoy transfection into TAMs on MA progression and mouse survival rates. Intraperitoneal injection of Man‐PEG bubble lipoplexes and US exposure transferred the NF‐κB decoy into TAMs effectively. When the NF‐κB decoy was delivered into TAMs by this method in the mouse peritoneal dissemination model, mRNA expression of the Th2 cytokine interleukin (IL)‐10 in TAMs was decreased significantly. In contrast, mRNA levels of Th1 cytokines (IL‐12, tumor necrosis factor‐α, and IL‐6) were increased significantly. Moreover, the expression level of vascular endothelial growth factor in ascites was suppressed significantly, and peritoneal angiogenesis showed a reduction. Furthermore, NF‐κB decoy transfer into TAMs significantly decreased the ascitic volume and number of Ehrlich ascites carcinoma cells in ascites, and prolonged mouse survival. In conclusion, we transferred a NF‐κB decoy efficiently by Man‐PEG bubble lipoplexes with US exposure into TAMs, which may be a novel approach for MA treatment.     

Novel immunotherapy for peritoneal dissemination of murine colon cancer with macrophage inflammatory protein-1beta mediated by a tumor-specific vector, HVJ cationic liposomes.

A critical issue for cancer treatment is control of metastatic or disseminated tumors. Although immune gene therapy has been considered as a possible strategy for treatment of such tumors, successful results have not yet been obtained. To evoke antitumor immunity more efficiently, macrophage inflammatory protein-1beta (MIP-1beta) was used for gene therapy of colon cancer in mice. Injection of hemagglutinating virus of Japan (HVJ) cationic liposomes-MIP-1beta into subcutaneous tumor masses resulted in local expression of MIP-1beta and local accumulation of CD4(+) T lymphocytes. Few studies of cancer gene therapies have targeted peritoneal dissemination. In a mouse model of peritoneal dissemination of colon tumor, we used a luciferase-based assay to demonstrate that HVJ cationic liposomes had high tumor specificity and were effective vectors for transfer of genes in peritoneal dissemination. When mice were treated by intraperitoneal injection of HVJ cationic liposomes containing the MIP-1beta gene, the survival periods of the MIP-1beta-treated mice were significantly longer than those of control mice. Therefore, this HVJ cationic liposome strategy may serve as a powerful tool against peritoneal disseminated cancer.     

Indoleamine 2,3‐dioxygenase promotes peritoneal metastasis of ovarian cancer by inducing an immunosuppressive environment

Indoleamine 2,3‐dioxygenase (IDO) is a tryptophan‐catabolizing enzyme that has immunoregulatory functions. Our prior study showed that tumoral IDO overexpression is involved in disease progression and impaired patient survival in human ovarian cancer, although its mechanism remains unclear. The purpose of the present study is to clarify the role of IDO during the process of peritoneal dissemination of ovarian cancer. Indoleamine 2,3‐dioxygenase cDNA was transfected into the murine ovarian carcinoma cell line OV2944‐HM‐1, establishing stable clones of IDO‐overexpressing cells (HM‐1‐IDO). Then HM‐1‐IDO or control vector‐transfected cells (HM‐1‐mock) were i.p. transplanted into syngeneic immunocompetent mice. The HM‐1‐IDO‐transplanted mice showed significantly shortened survival compared with HM‐1‐mock‐transplanted (control) mice. On days 11 and 14 following transplantation, the tumor weight of peritoneal dissemination and ascites volume were significantly increased in HM‐1‐IDO‐transplanted mice compared with those of control mice. This tumor‐progressive effect was coincident with significantly reduced numbers of CD8⁺ T cells and natural killer cells within tumors as well as increased levels of transforming growth factor‐β and interleukin‐10 in ascites. Finally, treatment with the IDO inhibitor 1‐methyl‐tryptophan significantly suppressed tumor dissemination and ascites with reduced transforming growth factor‐β secretion. These findings showed that tumor‐derived IDO promotes the peritoneal dissemination of ovarian cancer through suppression of tumor‐infiltrating effector T cell and natural killer cell recruitment and reciprocal enhancement of immunosuppressive cytokines in ascites, creating an immunotolerogenic environment within the peritoneal cavity. Therefore, IDO may be a promising molecular target for the therapeutic strategy of ovarian cancer.     

A new temperature-sensitive liposome for use with mild hyperthermia: characterization and testing in a human tumor xenograft model

The single biggest challenge now facing drug delivery (for liposomes and indeed other carriers) is to initiate and produce release of the encapsulated drug only at the diseased site and at controllable rates. Our efforts have focused on developing a new thermal-sensitive drug delivery system, specifically for the local control of solid tumors. We describe here a new lipid formulation containing doxorubicin that has been optimized for both mild hyperthermic temperatures (39 degrees C to 40 degrees C) that are readily achievable in the clinic and rapid release times of drug (tens of seconds). This new liposome, in combination with mild hyperthermia, was found to be significantly more effective than free drug or current liposome formulations at reducing tumor growth in a human squamous cell carcinoma xenograft line (FaDu), producing 11 of 11 complete regressions lasting up to 60 days posttreatment.     

A case of advanced pancreatic cancer responding well to S-1/gemcitabine combination therapy after gemcitabine therapy

A 71-year-old male with unresectable pancreatic cancer treated with gemcitabine (GEM) by another doctor came to our hospital because of stenosis of duodenum and hydronephrosis. There was peritoneal dissemination in his abdominal cavity, and gastro-jejunostomy was performed. After surgery, GEM therapy was continued until he was judged as PD. The regimen was switched to S-1/GEM combination therapy. After that, the tumor marker was down to within normal range, and abdominal symptoms improved. He is now being treated as an outpatient. S-1/GEM combination therapy is effective for patients with unresectable advanced pancreatic cancer.     

Expression of vascular endothelial growth factor and E-cadherin in human ovarian cancer: association with ascites fluid accumulation and peritoneal dissemination in mouse ascites model.

Ascites formation and peritoneal dissemination are critical problems in patients with advanced ovarian cancer. Vascular endothelial growth factor (VEGF), also known as angiogenic growth factor, is a potent mediator of peritoneal fluid accumulation and angiogenesis of tumors. E-Cadherin is an adhesion molecule that is important for cell-to-cell interaction. To elucidate the molecular mechanism of ascites formation and peritoneal dissemination of ovarian cancer, we examined the expression of VEGF and E-cadherin in different ovarian cancer cell lines and utilized nude mice to compare the biological characteristics of ovarian cancer cells. Three human ovarian cancer cell lines (AMOC-2, HNOA and HTBOA) were used in this study. Expression of genes was analyzed by northern blotting and RT-PCR methods. AMOC-2 expressed E-cadherin, but not VEGF. HNOA expressed VEGF without E-cadherin expression. HTBOA expressed both VEGF and E-cadherin. Each human ovarian cancer model revealed a specific feature. The AMOC-2 mouse had a single large peritoneal tumor without ascites or remarkable peritoneal dissemination. HTBOA and HNOA mice had bloody ascites and marked peritoneal dissemination. Introduction of VEGF antisense into HTBOA cells could inhibit the ascites formation. It is suggested that VEGF is important for the ascites formation via the increased vascular permeability effect. The deregulation of E-cadherin expression might be involved in the peritoneal dissemination. These molecules are important for the formation of specific features of advanced ovarian cancer. Ovarian cancer cell lines that had different gene expression patterns produced nude mouse human ovarian cancer models with different characteristics.     

Expression of Vascular Endothelial Growth Factor and E-Cadherin in Human Ovarian Cancer: Association with Ascites Fluid Accumulation and Peritoneal Dissemination in Mouse Ascites Model

Ascites formation and peritoneal dissemination are critical problems in patients with advanced ovarian cancer. Vascular endothelial growth factor (VEGF), also known as angiogenic growth factor, is a potent mediator of peritoneal fluid accumulation and angiogenesis of tumors. E-Cadherin is an adhesion molecule that is important for cell-to-cell interaction. To elucidate the molecular mechanism of ascites formation and peritoneal dissemination of ovarian cancer, we examined the expression of VEGF and E-cadherin in different ovarian cancer cell lines and utilized nude mice to compare the biological characteristics of ovarian cancer cells. Three human ovarian cancer cell lines (AMOC-2, HNOA and HTBOA) were used in this study. Expression of genes was analyzed by northern blotting and RT-PCR methods. AMOC-2 expressed E-cadherin, but not VEGF. HNOA expressed VEGF without E-cadherin expression. HTBOA expressed both VEGF and E-cadherin. Each human ovarian cancer model revealed a specific feature. The AMOC-2 mouse had a single large peritoneal tumor without ascites or remarkable peritoneal dissemination. HTBOA and HNOA mice had bloody ascites and marked peritoneal dissemination. Introduction of VEGF antisense into HTBOA cells could inhibit the ascites formation. It is suggested that VEGF is important for the ascites formation via the increased vascular permeability effect. The deregulation of E-cadherin expression might be involved in the peritoneal dissemination. These molecules are important for the formation of specific features of advanced ovarian cancer. Ovarian cancer cell lines that had different gene expression patterns produced nude mouse human ovarian cancer models with different characteristics.     

A case report of advanced gastric cancer with carcinomatous ascites successfully treated by outpatient chemotherapy

The patient was a 54-year-old male with peritoneal dissemination and carcinomatous ascites of advanced gastric cancer. Although 4 months of temporary partial responses were obtained by a combination chemotherapy with TS-1 and DOC, retention of ascites appeared. Second-line combination chemotherapy with 5-FU and PTX was not effective, and we attempted to use intraperitoneal chemotherapy of low-dose CDDP. After 100 mg of CDDP had been administered, ascites almost disappeared. Then,intraperitoneal injection of low-dose CDDP and intravenous injection of 5-FU were given. Tumor marker decreased remarkably, and CT revealed reduction of peritoneal dissemination. These regimens seem to be effective in ambulant patients with advanced gastric cancer with peritoneal dissemination and carcinomatous ascites.     

A case of advanced gastric cancer with peritoneal dissemination responding remarkably to TS-1/CDDP combination chemotherapy

A 57-year-old woman visited a physician with complaints of anorexia and pollakiuria. Because a pelvic tumor and ascites were detected, she was referred to our department. Douglas pouch puncture revealed adenocarcinoma cells. Further examination showed an advanced gastric cancer with peritoneal dissemination. The cancer was judged to be unresectable. Chemotherapy with a combination of TS-1 and CDDP was performed before the operation. After 2 courses of the chemotherapy, her complaints disappeared, although abdominal CT confirmed remaining peritoneal dissemination. After 7 courses of chemotherapy, abdominal CT showed that the peritoneal dissemination had disappeared. Total gastrectomy and lymph node dissection were performed. Histological findings of the stomach revealed complete disappearance of cancer cells in the stomach and the regional lymph nodes. We confirmed that the TS-1/CDDP therapy resulted in a complete response to advanced gastric cancer and peritoneal dissemination. We recommend that chemotherapy be continued until the peritoneal dissemination disappears.     

Efficacy of oncolytic reovirus against human gastric cancer with peritoneal metastasis in experimental animal model

The prognosis of gastric cancer patients with peritoneal dissemination is extremely poor, and the development of an effective treatment is necessary. The aim of this study was to investigate the efficacy of oncolytic reovirus against peritoneal metastasis in human gastric cancer using an experimental animal model. Four human gastric cancer cell lines, including MKN45p, NUGC4, MKN7 and KatoIII, a normal NIH3T3 cell line as a control, and reovirus serotype 3, were used in this study. We evaluated the cytopathic effect of reovirus and the Ras activity in each gastric cancer cell line in vitro. To evaluate oncolytic efficacy in vivo, reovirus (1x10(8) PFU) was administered into the peritoneal cavity of nude mice on days 7, 8 and 9 after inoculation with MKN45p cells. Mean volume of ascites and the total number and weight of the peritoneal tumors were measured after sacrifice. After reovirus infection, cytopathic effect was observed in all four gastric cancer cell lines, but not in the control cells. Ras activation assay showed that Ras activity in all four gastric cancer cell lines increased to a higher level than that in the control cells. In the animal model experiments, mean volume of ascites and the total number and weight of the peritoneal tumors in the reovirus treatment group were significantly lower than those in the control group. In conclusions, intraperitoneal administration of reovirus could be useful as a new modality against peritoneal metastasis in gastric cancer.     

Tumor-targeting nanocomplex delivery of novel tumor suppressor RB94 chemosensitizes bladder carcinoma cells in vitro and in vivo.

PURPOSE: RB94, a truncated form of RB110, has enhanced tumor suppressor potency and activity against all tumor types tested to date including bladder carcinoma. However, efficient, systemic delivery of the gene encoding RB94 specifically to tumors, is an obstacle to clinical application as an anticancer therapeutic. We have developed a systemically given, nanosized liposome DNA delivery system that specifically targets primary and metastatic disease. The ability of RB94, delivered via this nanocomplex, to sensitize bladder carcinoma to chemotherapy in vitro and in vivo was assessed. EXPERIMENTAL DESIGN: The nanocomplex is an RB94 plasmid encapsulated by a cationic liposome, the surface of which is decorated with a tumor-targeting moiety, either transferrin (Tf/Lip/RB94) or an antitransferrin receptor single-chain antibody fragment (TfRScFv/Lip/RB94). The ability of the complex to sensitize human bladder carcinoma HTB-9 cells to chemotherapeutics was assessed in vitro by XTT assay. In vivo tumor specificity and efficacy were tested in mice carrying HTB-9 tumors by PCR and tumor growth inhibition, respectively. RESULTS: Transfection with Tf/Lip/RB94 significantly sensitized HTB-9 cells to chemotherapeutic agents in vitro. Tumor specificity of the complex was shown in an orthotopic bladder tumor model by immunohistochemistry and PCR. Moreover, in mice bearing subcutaneous HTB-9 tumors, the combination of systemically given Tf/Lip/RB94 or TfRScFv/Lip/RB94 plus gemcitabine resulted in significant (P<0.0005) tumor growth inhibition/regression and induction of apoptosis. CONCLUSIONS: Use of our tumor-targeting nanocomplex to specifically deliver the potent tumor suppressor RB94 efficiently to tumors has potential as a more effective treatment modality for genitourinary and other cancers.     

Low-dose gemcitabine concurrent with radiation therapy for locally advanced pancreatic carcinoma

We evaluated the efficacy and feasibility of low-dose gemcitabine concurrent with radiation as adjuvant therapy. Nine cases of locally far advanced unresectable pancreatic cancer were enrolled in this study. Intraoperative radiation was carried out in every case using eight or ten centimeter cones with a radiation dose of twenty to twenty five Gy. Postoperative radiation was two Gy per day on weekdays for five weeks. Low-dose gemcitabine (40 mg/m2) once a week was administered prior to radiation. A grade 3 adverse event occurred in three cases. CA19-9 decreased 60.1% and DUPAN-2, 52.6%. CT scan confirmed a necrotic change and a decrease of the tumor size. Average survival time was ten months. Peritoneal dissemination was the recurrence pattern. In conclusion, low-dose gemcitabine concurrent with radiation therapy may contribute to local control of the disease. However, peritoneal dissemination must be overcome to prolong survival.     

Liver metastasis from sigmoid colon cancer with peritoneal dissemination showed a complete response to TS-1

A 64-year-old man with unresectable sigmoid adenocarcinoma due to peritoneal dissemination (P3) and liver metastasis (H2) treated with TS-1, showed a complete response. TS-1 is an oral anticancer drug that produces biochemical modulation. It is composed of tegafur, gimestat and ostat potassium in a molar ratio of 1:0.4:1 to increase the effect of 5-FU and to decrease toxicity in the digestive canal. Treatment with TS-1 requires no hospitalization and can enhance the quality of life of the patient. TS-1 is expected to be an effective agent for the treatment of colon cancer with liver metastasis and peritoneal dissemination.     

Determination and modeling of kinetics of cancer cell killing by doxorubicin and doxorubicin encapsulated in targeted liposomes

Various mathematical approaches have been devised to relate the cytotoxic effect of drugs in cell culture to the drug concentration added to the cell culture medium. Such approaches can satisfactorily account for drug response when the drugs are free in solution, but the approach becomes problematic when the drug is delivered in a drug delivery system, such as a liposome. To address this problem, we have developed a simple model that assumes that the cytotoxic potency of a drug is a function of the intracellular drug level in a critical compartment. Upon exposure to drug, cell death commences after a lag time, and the cell kill rate is dependent on the amount of drug in the critical intracellular compartment. The computed number of cells in culture, at any time after exposure to the drug, takes into account the cell proliferation rate, the cell kill rate, the average intracellular drug concentration, and a lag time for cell killing. We have applied this model to compare the cytotoxic effect of doxorubicin (DOX), or DOX encapsulated in a liposome that is targeted to CD44 on B16F10 melanoma cells in culture. CD44 is the surface receptor that binds to hyaluronan and is overexpressed on various cancer cells, including B16F10. We have shown previously that the drug encapsulated in hyaluronan-targeted liposomes was more potent than was the free drug. The model required the determination of the cell-associated DOX after the cells were incubated with various concentrations of the free or the encapsulated drug for 3 h, and the quantification of cell number at various times after exposure to the drug. The uptake of encapsulated drug was greater than that of the free drug, and the ratio of cell association of encapsulated:free drug was 1.3 at 0.5 micro g/ml and increased to 3.3 at 20 micro g/ml DOX. The results demonstrate that the enhanced potency of the encapsulated drug could stem from its enhanced uptake. However, in certain cases, where larger amounts of the free drug were added, such that the intracellular amounts of drug exceeded those obtained from the encapsulated drug, the numbers of viable cells were still significantly smaller for the encapsulated drug. This finding demonstrates that for given amounts of intracellular DOX, the encapsulated form was more efficient in killing B16F10 cells than the free drug. The outcome was expressed in the kinetic model as a 5-6-fold larger rate constant of cell killing potency for the encapsulated drug versus the free drug. The model provides a quantitative framework for comparing the cytotoxic effect in cultured cells when applying the drug in the free form or in a delivery system.