Differential lysis of melanoma clones by autologous recombinant interleukin 2‐activated lymphocytes. Relationship with spontaneous resistance to doxorubicin (Dx)

Abstract
To investigate whether human melanoma cells intrinsically resistant to autologous LAKs do exist, and whether a relationship between the level of lysis of LAKs and spontaneous drug resistance can be identified at the clonal level, we studied 44 clones obtained from a metastatic melanoma lesion. The antigenic phenotype of clones revealed a marked heterogeneity in the expression of HLA antigens of classes I and II. The clones were subsequently tested for sensitivity to autologous LAK and for spontaneous resistance to Dx. No clone resistant to autologous LAK was found, although a considerable range of lysis was noted with a normal frequency distribution. Growth in agar of the 2 clones in which lysis was least pronounced (6 and 26) was completely inhibited after co‐culture with LAKs, indicating a lack of absolute resistance to these effectors, Spontaneous resistance to Dx, evaluated as ID50, revealed instead that the majority of clones had a low ID50. The frequency distribution of clones showed a left‐skewed curve. The percentage of specific 51Cr‐release and the ID50 for Dx could be correlated in 25 clones by linear regression. Sensitivity to LAK did not correlate with HLA classes I or II or melanoma‐associated antigen expression. These results support the contention that increased LAK sensitivity of tumor cells is associated with drug resistance.

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