Simultaneous cytokinetic measurement of aneuploid tumors and associated diploid cells following continuous labelling with chlorodeoxyuridine

S-phase cells of the lymphoplasmocytic compartment in hyperdiploid multiple myeloma are diploid cells

In vivo S-phase cell labeling with iododexoyuridine (IdUrd) was performed in six multiple myeloma (MM) patients. Myeloma cells from four patients were hyperploid. In three out of four patients, DNA/IdUrd flow cytometry revealed that most of the labeled cells, which had divided during the period, elapsed between flash labeling and sampling, had returned to the diploid G0/G1 compartment and not to the hyperdiploid peak. To eliminate contaminating cells belonging to the normal hematopoiesis, plasmocytic and lymphocytic cells were fractionated and analyzed separately. Cell enrichment was performed with use of murine monoclonal antibodies (MoAbs) against plasmocytic and lymphocytic cell markers and subsequent magnetic activated cell sorting with immunobeads, i.e., polysterene magnetic particles coated with sheep anti-mouse IgG. The purified plasmocytic cells were mainly hyperdiploid and largely unlabeled. The lymphocytic cells appeared to belong chiefly to the diploid cell population. The IdUrd-labeled cells were predominantly lymphocytic cells, returning after mitosis to the diploid G0/G1 peak. Although this pattern of S-phase cells in hyperdiploid MM, belonging to the diploid cell compartment, was observed in three out of four hyperploid cases and although the number of observations is small, S-phase cells may demonstrate an aspect of tumor cell kinetics in hyperploid MM, which has been debated for many years and which indicates the existence of a non-plasmocytic stem cell compartment that feeds the plasmocytoma. The behavior of the labeled cells as observed in a few cases of MM provides another, hitherto undescribed, argument that, at least in some MM patients, a part of the proliferating tumor cells may be diploid lymphocytic (precursor) cells. These findings should be considered when targeting and monitoring treatment of MM and also in purging procedures of bone marrow in patients to be treated by ablative cytotoxic therapy and autologous bone marrow transplantation.

Cellular kinetics in rectal cancer

Measurements of dynamic tumour cell kinetic parameters, particularly the potential doubling time (Tpot) may have potential as predictive assays for treatment outcome after radiotherapy. This paper details the distributions of Tpot and other kinetic and DNA content parameters measured in rectal cancers. Biopsies were taken from 119 patients approximately 6 h after infusion of 200 mg m-2 bromodeoxyuridine (BrdUrd). The samples were analysed by bivariate DNA/BrdUrd flow cytometry. The primary purpose of the study was to measure the kinetic parameters of labelling index (LI), duration of S-phase (TS) and Tpot. Secondarily, tumour DNA ploidy (DNA index) and S-phase fractions (SPFs) were also estimated from the univariate DNA histograms. The 101 evaluable patients were classified according to clinical stage as T2 (n = 12), T3 (n = 53), T4 (n = 28) or recurrent tumours (n = 8). Of the evaluable tumours, 73 were DNA aneuploid. The median LI, TS, and Tpot of the aneuploid tumours were 21%, 20 h and 3.3 days respectively. The calculated LI, TS, and Tpot of diploid tumours were subject to uncertainties because of the contribution of normal cells. The LI and SPF of all tumours were, however, significantly (P < 0.001) correlated, having a correlation coefficient of only 0.76. The wide distributions of values for LI (quartiles 13.5%, 26.9%) and Tpot (quartiles 2.4, 5.6 days) that were found are necessary baseline information if these parameters are to be useful in individual treatment selection or as predictors of treatment outcome.

Tumor cell kinetics in mixed populations

The delayed biopsy, relative movement method provides a rapid estimate of in situ potential doubling times in human tumors. The accuracy of the estimate, however, can be adversely influenced by normal diploid cells that are present in tumor biopsy specimens and have DNA profiles that overlap their tumor cell counterparts. Interference with the measurement of tumor cell kinetic parameters can result, the magnitude of which depends upon the DNA index and the proportion and labeling index of these normal cells. Two approaches that address this problem were explored in vitro: (1) A normal cell subtraction method was developed in which adjacent normal tissue and tumor are biopsied concurrently and are separately processed for flow cytometric analysis. Results are integrated to allow an approximate correction for the normal, diploid population's perturbation of the measurement of tumor labeling index and relative movement. This approach was examined in this present study through extensive testing in mixtures of various proportions of two in vitro cell lines. (2) The percent S phase method, developed by Durand, was examined in these same population mixtures, as well as separately in each population. Both methods provide reliable estimates of kinetics in mixed in vitro populations. The relative advantages and disadvantages of each, as well as the potential limitations if extended to in vivo measurements, are discussed.