For many compounds (neurotrophic factors, antibodies, growth factors, genetic vectors, enzymes) slow diffusion in the brain severely limits drug distribution and effect after direct drug admistration into brain parenchyma.We investigated convection as a means to enhance the distribution of the large and small molecules 51In-labeled trserrin (111In-Tf; Mr, 80,00)

Lysis of tumor cells by activated cytotoxic lymphocytes requires their recognition of antigens associated with major histocompatibility complex molecules. The authors studied the constitutive expression of Class I and Class II major histocompatibility complex antigens on mouse brain-tumor cells and the capacity of different cytokines and cytokine combinations to alter this expression in vitro. Cells from the murine glioma 26 (GL26), glioma 261 (GL261), and ependymoblastoma A (EpA) cell lines were established in monolayer culture and treated for 48 hours with either alpha interferon, gamma interferon, tumor necrosis factor alpha, tumor necrosis factor alpha plus gamma interferon, or interleukin-2. They were then analyzed by flow cytometry for baseline and cytokine-altered major histocompatibility complex expression. All cell lines had a similar constitutive major histocompatibility complex pattern with low Class I antigen expression and no detectable Class II antigen expression. Alpha interferon substantially induced and up-regulated Class I antigen expression, but had no effect on Class II antigen expression. Gamma interferon also stimulated up-regulation of Class I antigen expression, generally doubling the anti-Class I antigen fluorescence of treated cells. Its effect on Class II antigen expression was more extensive. In the GL26 and GL261 cell lines the expression of Class II antigen determinants increased to 12 x and 14 x control values and as many as 75% of cells that had no detectable constitutive expression of Class II antigen expressed this antigen after priming with gamma interferon. The addition of tumor necrosis factor alpha to gamma interferon further increased Class II antigen expression on EpA tumor cells only. Interleukin-2 and tumor necrosis factor alpha alone had no effect on Class I or Class II antigen expression of any cell lines. It is concluded that Class I and Class II antigen expression in mouse glioma cell lines is induced and enhanced after treatment with certain cytokines in vitro. Use of these cell lines to create in situ primary brain tumors in C57BL/6 mice should provide an excellent animal system to study major histocompatibility complex modulation in brain tumor cells and to examine the potential impact of major histocompatibility complex up-regulation on the response of brain tumors to immunotherapy.

Targeted protein toxins are a new class of reagents with the potential for great tumor selectivity and cytotoxic potency. Two such compounds were studied: 1) Tf-CRM107, a conjugate of human transferrin (Tf) and diphtheria toxin with a point mutation (CRM107); and 2) 454A12-rRA, a conjugate of a monoclonal antibody (454A12) to the human Tf receptor and recombinant ricin A chain (rRA). Both compounds are potent and specific in killing human glioblastoma cell lines in vitro. The authors investigated the activity of these reagents administered intratumorally against solid U251 MG human gliomas in vivo. Nude mice with established U251 MG flank tumors (0.5 to 1.0 cm in diameter) were randomly assigned to be treated with 100-microliters intratumoral injections of Tf-CRM107 (10 micrograms) or 454A12-rRA (10 micrograms), equimolar doses of CRM107 (4.3 micrograms), 454A12 antibody (7.5 micrograms), or rRA (1.5 micrograms), or phosphate-buffered saline (PBS) every 2 days for a total of four doses. Tumor volume and animal weight were assessed by a blinded observer before each treatment and biweekly for 30 days after initiating therapy. With Tf-CRM107 administration, tumor regression of greater than 95% occurred by Day 14 (p < 0.01) and tumors did not recur by Day 30. Treatment with 454A12-rRA caused a 30% decrease in tumor volume by Day 14 (p < 0.01). Treatment with equimolar doses of the unconjugated targeted protein toxin components CRM107, 454A12, or rRA caused significant U251 MG tumor growth inhibition, but the effects were less potent than the antitumor effects of the conjugates. This study also characterized the dose-response effect of Tf-CRM107 on tumor growth and tumor weight on Day 30. Nude mice with established U251 MG flank tumors (0.5 to 1.0 cm in diameter) were treated with 100-microliters intratumoral injections of 10, 1.0, or 0.1 microgram of Tf-CRM107 or PBS every 2 days for a total of four doses. All three doses of Tf-CRM107 significantly inhibited tumor growth by Day 14 (p < 0.01) and at Day 30 (p < 0.05), with a significant dose-response relationship. This study demonstrated in vivo efficacy of the targeted toxins Tf-CRM107 and 454A12-rRA against a human glioma. With intratumoral administration, the effect of Tf-CRM107 was tumor-specific and in some animals curative. Regional therapy with these potent tumor-specific agents using direct intratumoral infusion should limit systemic toxicity and may be efficacious against brain tumors.

(Folia Morphol 2013; 72, 4: 306-310)