Two siblings with acute T-cell lymphocytic leukemia

Tumour-induced host stromal-cell transformation: induction of mouse spindle-cell fibrosarcoma not mediated by gene transfer

Tumour-induced host-cell transformation has been addressed by examining human tumours in situ and following xenograft to nude mice. We have found evidence for the transformation of host stromal fibroblasts both in vivo and following the introduction of the tumours to in vitro culture. The in vitro culture of one such xenograft--derived from a human prostatic adenocarcinoma--resulted in the outgrowth of a transformed aneuploid mouse cell line. This transformed line was tumourigenic both in BALB/c nu/nu (nude) mice and in heterozygous nu/+mice, with the morphology of a spindle-cell sarcoma. The cell line did not express human isozymes or human histocompatibility antigens, nor were human chromosomes present. Moreover, human DNA sequences were not detected by human Alu repeat sequence element probing in the transformed cell line grown either in vitro or in vivo. The line contained retroviral long terminal repeat sequences but there was no evidence of proviral activation. These findings indicate that tumour cells may cause transformation of neighbouring stromal cells; that this transformation may proceed in the absence of DNA transfer or activation of endogenous proviruses; and that the means of this observed transformation may involve humoral factors elaborated by the tumour cells.

Evidence for HLA-linked susceptibility factors in childhood leukemia

To test the hypothesis that susceptibility to leukemia can be governed by (a) recessive gene(s) associated with the major histocompatibility complex (MHC) in man, we performed an analysis of the inheritance of HLA antigens in 55 families in which one of the children developed ALL. We found among the parents of affected children a highly significant increased compatibility at the DR locus (p = 0.003). A similar increase was observed in sharing HLA antigens of the B locus (p = 0.02). The observed number of homozygotes among the patients was twice the expected value in families where the parents shared a B and a DR antigen. In segregation analysis, heterozygotes for the shared parental HLA antigen were significantly more prevalent among the healthy siblings. Our genetical analysis indicates that mating of certain shared alleles of the HLA system (especially of the DR locus) is associated with the risk for the offspring to develop ALL in childhood. This situation favors the expression of recessive genes associated with the MHC, and presumably those involved in the susceptibility to acute leukemia. Because familial leukemia is a rare event, the susceptibility to childhood ALL must also implicate genes outside the MHC and important environmental factors.