Composite tissue allotransplantation in chimeric hosts: part I. Prevention of graft-versus-host disease

BACKGROUND: Mixed allogeneic chimerism (MAC) has been shown to induce tolerance to composite tissue allografts (CTA). However, transplantation of unmanipulated donor-specific limbs results in severe graft-versus-host disease (GVHD). This suggests that nontolerant mature donor-derived cells in the CTA may affect the stability of chimerism, potentially resulting in GVHD. The aim of this study was to develop an approach to study and prevent GVHD in a mixed chimeric-rat hind-limb transplantation model. METHODS: [ACI-->WF] chimeras received a limb from Wistar Furth (WF) (syngeneic), Fisher (third-party), or ACI (irradiated [1,050 cGy] or nonirradiated) rats. In vitro tolerance was assessed using mixed lymphocyte reactivity (MLR) assays at the time the animals were killed. RESULTS:[ACI-->WF] chimeras with greater than 85% chimerism exhibited rejection-free survival of donor-specific hind limbs. However, 100% of these animals developed lethal GVHD 22.4+/-2.8 days after limb transplantation. [ACI-->WF] chimeras that underwent transplantation with irradiated ACI or syngeneic WF limbs showed no signs of rejection or GVHD at 5 months. Nonchimeric and third-party controls rejected limbs within 10 days. CONCLUSIONS: Conditioning of the host WF rats with 950 cGy of irradiation (sublethal, myeloablative) led to high levels of MAC without GVHD. The mature T-cell content of nonirradiated donor (ACI) limbs was sufficient to induce lethal GVHD in 100% of tolerant mixed chimeric [ACI-->WF] hosts. Irradiation of donor limbs before transplantation resulted in long-term donor-specific tolerance and prevented GVHD. These data demonstrate that (1) established chimeras could be susceptible to GVHD caused by immunocompetent donor cells transferred with the hind limb, and (2) inactivating these cells with irradiation prevents GVHD and destabilization of chimerism, and permits rejection-free graft acceptance.     

A new targeting approach for breast cancer gene therapy using the heparanase promoter

Gene therapy with adenoviral (Ad) vectors is a promising new approach in the treatment of cancer. Strategies to restrict adenoviral-mediated transgene expression are important to avoid gene transfer into normal cells. Heparanase (HPR) is overexpressed in breast cancer but downregulated in differentiated normal tissue. Expression of the HPR gene was evaluated in breast cancer cells. Biodistribution and liver tropism was evaluated in a mouse model. HPR is highly expressed in breast cancer tissue. The HPR promoter retained its fidelity in an adenovirus context and was activated in breast cancer cells but showed low activity in normal breast cells and the murine liver. We conclude that the HPR pathway is a promising target for the development of breast cancer directed gene therapy strategies.     

Current developments in adenovirus-based cancer gene therapy

Adenovirus (Ad)-based cancer gene therapy is a promising, novel approach for treating cancer resistant to established treatment modalities. Unfortunately, the efficacy of nonreplicative first generation Ads was low and data from clinical trials were disappointing. To address this problem, conditionally replicating Ads have been constructed. Infection of tumor cells with conditionally replicating Ads results in tumor-specific replication, subsequent oncolysis and release of the virus progeny. Recently, it has been suggested that the low expression of the coxsackie-Ad receptor is the rate-limiting factor for infectivity with serotype 5 (Ad5). Unfortunately, coxsackie-Ad receptor expression is highly variable and often low on many tumor types. Consequently, molecular strategies have been applied for the development of coxsackie-Ad receptor-independent oncolytic Ads. This review describes recent developments of Ad-based cancer gene therapy, including novel engineering techniques of the Ad capsid for efficient tumor targeting, as well as targeting techniques, to restrict transgene expression to cancer cells.     

Individual variation of cortical surface area asymmetries

Asymmetries in the size of cortical regions are regularly associated with functional lateralization. Assessment of cortical asymmetry is often confounded by measurement artifact and a lack of information about the normal variance of asymmetry in regions that are functionally symmetric. In order to measure hemispheric asymmetries in the surface area of cortical gyri, magnetic resonance (MR) images were acquired from 10 normal, right-handed males. Computer representations of the cortical surface in all 20 hemispheres were reconstructed from the images by first creating a white matter model and then 'inflating' it to approximate the cortical surface. The advantage of this approach is that it accurately models the deep sulci as well as the cortical surface. Surface area measurements of the whole hemisphere, the postcentral and the cingulate gyrus were collected from each subject. For each region an asymmetry score was computed based on the difference in the surface area of the left and right regions. Many subjects showed asymmetries in these two gyri; however, the mean asymmetry scores were never significantly asymmetric. The large variability of individual asymmetry scores indicates that cortical asymmetries may be present even in the absence of clear functional asymmetry. An understanding of the degree of asymmetry in structures that do not show clear functional lateralization is critical for interpreting data gathered from cortical regions that are functionally asymmetric.      

Carcinoma of the colon: irradiation by delayed split whole-abdominal technique

Locally advanced and recurrent colon cancer was treated by irradiating first the pelvis and two hours later the upper abdomen. Curative treatment consisted of 4,000-5,000 rad (40-50 Gy) in 200-rad (2-Gy) fractions to the pelvis and 3,000 rad (30 Gy) in 150-rad (1.5-Gy) fractions to the upper abdomen. Palliative treatment consisted of 2,100 rad (21 Gy) in 300-rad (3-Gy) fractions to the liver, 3,000 rad (30 Gy) in 150-rad (1.5-Gy) fractions to the upper abdomen, and 4,000-5,000 rad (40-50 Gy) in 200-rad (2-Gy) fractions to the pelvis. Treatment was tolerated well, and acute toxicity was limited. Seven of the 11 patients treated curatively remain free of abdominal disease after 10-35 months; median survival among 9 patients treated palliatively was 9 months.