Combined administration of Onconase and VCR yields enhanced cytotoxicity in vitro and in vivo against human colon carcinoma cells that overexpress the mdr1 gene.

One strategy to overcome multidrug resistance in neoplasia is to inhibit the gp170 glycoprotein (relative molecular mass, 170,000) that functions as a plasma membrane, energy-dependent, drug-efflux pump. The human colon cancer cell line HT-29, which grows as an ascitic tumor in athymic NCr-nu/nu nude mice, was made multidrug resistant by infection with an MDR1 (also known as PGY1) retrovirus. Referred to as HT-29mdr1, it was used to study reversal of drug resistance in vivo by the anti-P-glycoprotein monoclonal antibody MRK-16. Flow cytometry and radioimmunoassay demonstrated a marked increase in MRK-16 reactivity on HT-29mdr1 cells as compared with its reactivity on the parental, uninfected cell line (HT-29par). The 50% inhibitory concentrations (IC50) of vincristine on HT-29par and HT-29mdr1 cells were 2.5 and 15 ng/mL, respectively. The MRK-16 monoclonal antibody did not affect the vincristine sensitivity of the HT-29par cells. Pretreatment of HT-29mdr1 cells with 10 micrograms/mL MRK-16 in tissue culture partially restored the vincristine sensitivity (IC50 = 7 ng/mL). This modulation of vincristine sensitivity by MRK-16 was then tested in vivo. The median survival times of mice given intraperitoneal transplants of 5 x 10(6) HT-29par or HT-29mdr1 were 37 and 39 days, respectively. Treatment of mice with 1 mg/kg vincristine weekly for 3 weeks, beginning 10 days after tumor injection, resulted in a significant increase in the median survival time of the HT-29par tumor-bearing mice (68 days, P less than .0001), but it had no effect on the HT-29mdr1 tumor-bearing mice. However, treatment of mice bearing the HT-29mdr1 tumor with MRK-16 before vincristine therapy reversed the resistance to the drug (median survival time = 64 days, P less than .0001). The MRK-16 monoclonal antibody alone had no effect on the median survival time of mice given an injection of either HT-29par or HT-29mdr1 cells. These results suggest that strategies employing monoclonal antibody against gp170 may be clinically useful to reverse multidrug resistance.

MRK-16 used in combination with rHuIFN alpha-2a was significantly more effective than MRK-16 in overcoming multidrug resistance.

In patients with stage IIB-III disease, adjuvant high-dose interferon-alpha2b has shown clinical benefit, although metastatic melanoma is currently without any known survival-prolonging therapy. Angiogenesis has been considered important in melanoma progression, and endostatin is an angiogenesis inhibitor with antitumor activity that has shown promising results in murine model systems, prompting investigation of a formulation of rh-Endostatin (EntreMed, Rockville, Maryland, USA) alone and with interferon in metastatic melanoma. Patients were randomly assigned to receive interferon alpha2b (Schering-Plough) 10 million units/m(2) subcutaneously three times a week plus rh-Endostatin 45 mg/m(2) subcutaneously every 12 h (arm A) vs. rh-Endostatin alone (arm B). Twenty-one patients (age range 31-77 years, median age 54, 12 men and nine women, 17 cutaneous, and four ocular melanomas) were enrolled. No antitumor responses were observed, and no significant differences were noted in time to progression or overall survival. Two patients had stable disease enduring more than 30 weeks on treatment. Serum endostatin levels increased significantly 4 weeks after treatment in both groups. Basic fibroblast growth factor levels in urine were significantly lower following treatment in patients on arm B (P=0.043). The percentage of circulating endothelial cells was increased in five evaluable patients 4 weeks after treatment. Low titer (

The mechanisms that regulate the adhesion and migration of NK cells to and across endothelium have been studied under nonflow conditions; however, the involvement of these processes in vivo is poorly understood. The present studies investigated the potential vascular adhesion ligand interactions that determine the in vivo recruitment of NK cells to pulmonary and hepatic parenchyma, and s.c. tumor after treatment of mice with biologic response modifiers. Seventy-two hours after a single injection of the cytokine-inducing agent poly-L-lysine stabilized in carboxylmethyl cellulose (poly-ICLC), pulmonary NK cell lytic activity and N-alpha-carbobenzoxy-L-lysine thiobenzyl ester (BLT)-esterase were augmented 29- and 14-fold, respectively, and the number of lung-associated NK cells was increased from 2.3 x 10(5) to 7.4 x 10(5). Similar fold increases in NK cell number and activity were observed in the liver and s.c. B16 melanoma after poly-ICLC injection or in the lungs and liver of mice treated with IL-2. Concomitant treatment of mice with alpha-VCAM-1 or alpha-VLA-4 mAb, but not alpha-ICAM-1 or alpha-LFA-1, abrogated the poly-ICLC and IL-2-induced increase in organ-associated NK activity and percentage of tumor-associated NK cells, resulted in a 61 to 76% decrease in pulmonary and hepatic NK cell number, and was independent of T and/or B cells. The decrease in NK cell number in organ parenchyma and tumor lesions was correlated to an increase in the number of NK cells in peripheral blood, but not bone marrow. These results demonstrate that VCAM-1/VLA-4 interaction is critically involved in the infiltration of newly recruited NK cells in to lung, liver, and progressively growing tumor after mobilization from the bone marrow.