CHROMOSOMES AND THE LEUKAEMIC PROCESS 105 



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DISCUSSION 



mole: I would draw the opposite conclusion. If, in fact each leukaemia is in any sense 

 unique, then you woiildn't expect the chromosomes to be the same. I would expect that 

 something that was aetiologically important should in fact be different in each leukaemic 

 line so that the fact that each individual leukaemia appears to be unique karyotjT)icaUy 

 seems to me to be sensible. That doesn't obviate your objection — a perfectly real one — 

 that all the chromosomal changes could be epiphenomenal. But I think it's wrong to 

 expect that one should get a consistent change. Recent evidence confirms that the 

 Philadelphia chromosome is not in fact a consistent findmg m chronic myeloid leukaemia. 

 Last week the Edinburgh people reported two cases of ankylosuag spondylitics with 

 chronic myeloid leukaemia without the PhUadelpliia cliromosome in either of them. One 

 could perhaps say that if the Philadelphia chromosome was a consistent finding in 

 chronic myeloid leukaemia, this would be evidence that chronic myeloid leukaemia was 

 not itself neoplastic. It only became neoplastic with the acute myeloid transformation 

 with wliich it so often terminates, and then you do get karyotypic multiformity. 

 koller: Each case must really be judged on its own. I consider that to make such a 

 sweeping statement as "every leukaemia arises from a cliromosomal abnormahty" is 

 quite illogical. 



ilbery: May I resolve this apparent conflict? Does it matter if there are cells with a mode 

 greater than 40 present? Surely the point is that there are abnormal cells present at all. 

 Cells with greater chromosome numbers can't be without influence on adjacent normal 

 cells. 



ALEXANDER: I have been working with a murine leukaemia which was originally pro- 

 duced by Law many years ago and carried in tissue culture subsequently for 5 or 6 years. 

 Smgle cells are sufficient for transplantation of this tumour. Clones can be origmated in 

 tissue culture from single ceUs and thus one can start off with a geneticaUy pure line. Dr. 

 Davies has looked at these for us and he tells us that they are strictly diploid — I think 

 something like 90% diploid in spite of the fact that they've been in tissue culture for so 

 many years. We now have a number of mutants with different characteristics, e.g. 

 different radiosensitivities, yet they have still 40 cliromosomes. Certauily Prof. KoUer's 

 conclusion that one cannot say that leiikaemia is invariably associated with changes in 

 chromosome number seems to be very weU exemplified here. 



lajvierton: May I ask whether with trisomies you have much variation in the morpho- 

 logy of one or more of the cliromosomes? If you don't, it's a bit difficult to see why you 



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