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The Cytologic and Growth Characteristics of Tumor and Normal Clones of Picea glauca¹

Department of Biology, The Pennsylvania State University, McKeesport, Pennsylvania 15132

Comparative chromosomal, mitotic, and growth studies were made utilizing several series of tumor and normal clones of Picea glauca (white spruce) tissue grown in vitro. Both primary and secondary cloned lines, descending from one primary tumor explant, exhibited a much greater heterogeneity with respect to chromosome number, rate of cell division, and rate of growth, among themselves, than those yielded from one normal explant.

The establishment of clonal derivatives through single-cell isolations was found to be the most effective method of securing cell populations with homogenous genetic make-up. Clones with both normal and irregular chromosome numbers obtained from one primary explant of normal and one primary explant of tumor cells kept their chromosome complements for over thirty passages. Throughout this study highly significant correlations were found among growth rate, rate of cell division, and chromosome number in both the tumor and the normal clones. Clones with higher chromosome numbers exhibited higher rates of growth and higher rates of cell division. All types of tumor clones, including those with varying degrees of aneuploidy, appeared to be able to grow indefinitely.

It is postulated that, in the fully developed tumor cell, a series of biosynthetic systems are permanently accelerated and that the degree of acceleration determines the growth potentials, which can be predicted with a fair degree of accuracy from the cells' mitotic frequency or chromosomal alterations.

¹ Supported by Grants E-319 and E-319A from the American Cancer Society, by the NSF Institutional Fund for Research, and by a grant from The Society of the Sigma Xi and the Scientific Research Society of America.

Received 7/27/67. Accepted 11/26/67.