Comment on ‘Predicting recurrence in axillary node negative breast cancer patients’, by Rosner and Lane

on behalf of the Nottingham Breast Unit     

Antigen processing and presentation by EBV-carrying cell lines: Cell-phenotype dependence and influence of the EBV-encoded LMP1

Burkitt's-lymphoma (BL) lines which have maintained in vitro the tumor-cell phenotype (group-1 BLs) are poor antigen- presenting cells (APC), in spite of a relatively high surface expression of MHC class II. In order to investigate the mechanism of this deficiency, we have compared group-1 BL lines, their sub-lines which have progressed in vitro towards an LCL-like phenotype (group-III BL), and EBV-transformed lymphoblastoid cell lines (LCLs), for their ability to bind and process tetanus toxoid (TT). The uptake and internalization of ¹²⁵I-labelled TT was equivalent in the 3 cell types. Only LCLs and group-III BL lines were able to process the IT,as shown by the identification of discrete proteolytic products after separation of whole-cell extracts in tricine-SDS-polyacrylamide gels, and by the recovery of TCA-soluble radioactivity in the culture supernatant. Processing of TT was induced by expression of the EBV- encoded membrane protein LMPI in transfected group-I BLs. The present findings suggest that the inability of group-I BLs to act as APC is due to their failure to process exogenous antigens. This function appears to be related to phenotypic properties that can be modulated by the expression of LMPI.     

Neural and musculoskeletal contributions to the development of stance balance control in typical children and in children with cerebral palsy

Studies on the development of automatic postural responses in both typically developing children and children with cerebral palsy were performed. With the appearance of "pull-to-stand" behavior, typically developing children first began to show muscle responses to platform movements in mainly the ankle muscles. With increased development, additional agonist muscles were added to the response pattern and a consistent distal to proximal sequence began to emerge. Well-organized responses were seen with the onset of independent stance and walking, along with the reduction of antagonist muscle co-activation. The older children with cerebral palsy who were pre-walkers had immature muscle activation patterns like those seen in the typically developing children at the pull-to- stand stage of development. These included disorganized muscle responses and increased frequency of coactivation of both proximal–distal and agonist–antagonist muscles. In order to determine if musculoskeletal constraints contributed to these response patterns, normal children were asked to stand in a crouched posture similar to that of children with CP. This caused postural muscle response patterns to more closely approximate those of children with spastic diplegia.     

Inhibitors of tyrosine kinases in the treatment of psoriasis

Psoriasis is a heterogenous skin disease, characterized by epidermal hyperproliferation, abnormal keratinization and inflammation. The heterogeneity of the disease results probably from the interaction of multiple gene abnormalities with environmental factors. The new approaches to drug design have become refocused to the emerging understanding of the role of signaling pathways in health and disease. Protein tyrosine kinases (PTKs) regulate cell proliferation, differentiation and immune processes. Uncontrolled signaling from receptor and intracellular tyrosine kinases can lead to numerous proliferative diseases: cancer, leukemia, restenosis and psoriasis. Identification of PTKs that play a key role in a defined disease can lead to a selective drug. The balance of signals which regulate the homeostasis of normal epidermis is altered in psoriasis. Several lines of evidence suggest a role for the EGF receptor system in this process. Therefore, blockers of the EGFR kinase were suggested as potent antipsoriasis agents. PTK inhibitors from the tyrphostin family were found to block EGF - dependent cell proliferation. AG 1571 (SU 5271) potently inhibits ligand-induced autophosphorylation of EGF-R, downstream signal transduction events, DNA replication and cell cycle progression at micromolar concentrations, as well as proliferation of keratinocytes isolated from psoriatic lesions in excellent correlation with its EGFR kinase inhibitory activity in these cells. AG 1571 (SU 5271) has been in clinical trials by SUGEN Inc. since early 1997. Overexpression of the EGFR is the hallmark of most epithelial cancers. Therefore one can view blockers of the EGFR kinase as becoming universal inhibitors. Tyrphostins are the first signal transduction agents to be used in the clinic. This article summarizes recent progress in the development of PTK inhibitors in the treatment of psoriasis.     

Differences in the immunogenicity of latent membrane protein 1 (LMP1) encoded by Epstein-Barr virus genomes derived from LMP1-positive and -negative nasopharyngeal carcinoma

We have previously shown that an EBV-encoded latent membrane protein 1 (LMP1) gene derived from a nude mouse-propagated nasopharyngeal carcinoma (NPC) tumor and expressed in nonimmunogenic murine mammary carcinoma S6C cells failed to convey immunogenicity (rejectability) in syngeneic mice, whereas the corresponding B-cell derived LMP1 gene made the mice highly immunogenic. This raised the question of whether LMPL-expressing NPCs have been selected for low immunogenicity at the viral gene expression level. If so, LMP1-negative tumors that carry highly methylated LMP1 regulatory sequences may not have been exposed to a similar immunoselection. In the present study, we have compared LMP1 genes derived from two LMP1-positive NPCs and two LMP1-negative NPCs. All four genes were expressed in S6C cells in parallel with the previously tested isolates from a B-cell (B95-8)-derived and a nude mouse-propagated NPC (Cao)-derived gene. As in the previous study, we have found that the B-cell-derived LMP1 isolate was highly immunogenic. LMP1-positive tumor-derived isolates were poorly immunogenic, whereas the isolates from the LMP1-negative NPC tumor had intermediate immunogenicity. Sequence data revealed that LMP1 genes from LMP1-expressing NPC had 16 amino acid substitutions, whereas LMP1 from non-LMP1-expressing NPC had only 9 amino acid changes in the coding region. Three of the changes were at shared sites, but with different modifications. The fact that the gene from non-LMP1-expressing NPC mutated at a low frequency but was more immunogenic than the LMP1 gene derived from LMP1-expressing NPC, which was highly mutated but less immunogenic, favors the idea that LMP1-positive tumors escape immunosurveillance in immunocompetent hosts by either a selective down-regulation of LMP1 expression, methylation in the LMP1 promoter sequence, or mutation of LMP1 in LMP1-expressing samples.