Findings from this study using a transplantable C3H mammary tumor failed to indicate interaction relative to growth parameters between two foci present in the same host. Whether they were growing alone or in the presence of a second focus, tumor growth rates were similar until the combined mass of multiple tumors approached that which was incompatible with survival. Only then was a difference in growth observed. Cytokinetic parameters, i.e. , labeling index, primer-dependent DNA polymerase index or growth fraction, DNA synthesis time, tumor doubling time, and cell cycle time, were also similar whether tumors grew alone or in the presence of a second focus. Following removal of a tumor, changes were observed within 24 hr in the kinetics of the residual focus. There was an increase in labeling index (duration ⋍ 10 days) and primer-dependent DNA polymerase index with a decrease in the tumor doubling time. Minimal change was noted in DNA synthesis time and cell cycle time. The kinetic changes observed were reflected in a measurable increase in tumor size ⋍ a week following tumor removal. Absence of an alteration in DNA synthesis time and cell cycle time indicates that the increase in tumor growth was probably due to a conversion of noncycling cells in Go phase into proliferation. Relationship of the findings to the use of adjuvant chemotherapy is considered.

https://cancerres.aacrjournals.org/content/canres/39/10/3861.full.pdf

Effect of Surgical Removal on the Growth and Kinetics of Residual Tumor

Ten permanent clones derived from a single biopsy specimen of an untreated human adenocarcinoma of the stomach were established and characterized in vitro. Tissue culture growth properties, doubling times, plating efficiencies, growth fractions, cell cycle phase distributions, DNA indices, modal chromosome numbers, and ploidies were determined. Growth fractions were nearly 100%, and doubling times ranged from 23 to 37 hr. The plating efficiencies were generally high for tumor cells in culture, ranging up to 70%. Modal chromosome numbers varied from 45 to 48, with a wider range of variability in about 25% of the cells studied in each clone. In addition, the parent cell line (from which the clones were isolated) was shown to grow in athymic mice and to have the same histochemical and cytological characteristics as the specimen taken from the patient. It is important to characterize human tumor cells in vitro in this detailed manner, since they serve as excellent model systems for other studies involving the heterogeneous responses to drugs and radiation. The identification of mechanisms of drug sensitivity and resistance and the testing of drug and radiation combination treatment schedules in such in vitro systems can provide valuable insight into the design of clinical protocols for treatment of stomach cancer in humans.

https://cancerres.aacrjournals.org/content/canres/43/4/1703.full.pdf

Establishment and characterization of an in vitro model system for human adenocarcinoma of the stomach

Cell proliferation kinetics in human solid tumors: relation to probability of metastatic dissemination and long-term survival.

It has been claimed that the commercially available Ki-67 monoclonal antibody recognizes a nuclear antigen which is solely expressed in cycling cells Therefore, at present, Ki-67 is increasingly used as a tool in evaluating growth fractions (GFs) of human tumors Here we describe specific patterns in the expression and topological distribution of this antigen during the cell cycle in MCF-7 human breast cancer cells Our results support earlier findings that the antigen belongs to a class of antigens associated with the structural organization of meta- and anaphase chromosomes, and proteins located near the cortical regions of prenucleolar bodies and nucleoli Using 5′-bromodeoxyuridine-labeling technology, we show that the expression may be undetectably low at the onset of DNA replication Comparison of Ki-67 fractions (KFs) and GFs as estimated from continuous 5′-bromodeoxyuridine-labeling curves revealed that KF was invariably higher than GF: in exponentially growing cov362c14 human ovary cancer cells, KF was only 35% higher than GF; in MCF-7 cells, 113 ± 46% In MCF-7 cultures either growing under suboptimal conditions or treated with 10-6m tamoxifen, the difference was more pronounced Furthermore, we evaluated the decrease of Ki-67-positive cells in nutritionally deprived and cell cycle-specific, drug-treated cultures Since the results indicate that nonproliferating cells may retain the antigen for a considerable period of time, KF may not always be a reliable indicator of GF

https://cancerres.aacrjournals.org/content/canres/49/11/2999.full.pdf

Nuclear distribution of the Ki-67 antigen during the cell cycle: comparison with growth fraction in human breast cancer cells.

We have established and studied a colony of mice with a unique trait of host resistance to both ascites and solid cancers induced by transplantable cells. One dramatic manifestation of this trait is age-dependent spontaneous regression of advanced cancers. This powerful resistance segregates as a single-locus dominant trait, is independent of tumor burden, and is effective against cell lines from multiple types of cancer. During spontaneous regression or immediately after exposure, cancer cells provoke a massive infiltration of host leukocytes, which form aggregates and rosettes with tumor cells. The cytolytic destruction of cancer cells by innate leukocytes is rapid and specific without apparent damage to normal cells. The mice are healthy and cancer-free and have a normal life span. These observations suggest a previously unrecognized mechanism of immune surveillance, which may have potential for therapy or prevention of cancer.

/pdf/spontaneous-regression-of-advanced-cancer-identification-of-wn3tbz05bv.pdf

Spontaneous regression of advanced cancer: identification of a unique genetically determined, age-dependent trait in mice.

The tumor growth fraction measured by the percentage labeled mitoses method has been determined in transplantable solid and ascites murine tumors, the latter being measured at different times after transplantation. These values were compared to an in vitro , autoradiographic assay that determines the fraction of cells in a given population (primer-available DNA-dependent DNA polymerase index) that have both nuclear DNA-dependent DNA polymerase and DNA capable of acting as primer-template. It appears that almost all cells with a short G1 phase duration (<19 hr) that are within the proliferative cycle are primer-available DNA-dependent DNA polymerase positive. The results of the comparison indicate that the primer-available DNA-dependent DNA polymerase index estimation of growth fraction is very nearly identical to the growth fraction measured by the percentage labeled mitoses method.

https://cancerres.aacrjournals.org/content/canres/36/7_Part_1/2415.full.pdf

Estimation of tumor growth fraction in murine tumors by the primer-available DNA-dependent DNA polymerase assay.

A technique has been developed allowing the autoradiographic detection of incorporation of 3H-thymidine-5′-triphosphate (3H-TTP) into nuclear DNA of smears of Sarcoma-180 (S-180) mouse ascites tumors under the direction of the cell's own nuclear DNA polymerase. Dried smears are dipped into an agar solution, which strips cytoplasm from the nuclei, and are then air dried and incubated with a buffered mixture containing four nucleotide triphosphates (one labeled), Mg++, and Ficoll, with the cell's own DNA acting as primer. The incorporation of 3H-TTP into the nuclei, like the cell free DNA polymerase assay, is largely dependent on the presence of all four nucleotide triphosphates and Mg++ and produces a product which is DNase sensitive and RNase resistant.



DNA polymerase activity, as studied in a cell free assay, decreases with tumor age. This correlates well with a decreasing 3H-TTP labeling index in autoradiographs of aging tumors. The 3H-TTP labeling index has also been shown to exceed but parallel the in vivo3H-thymidine (3H-TdR) pulse labeling index for all tumor ages examined.



In at least some cell systems DNA polymerase seems characteristic of cells in cycle. The autoradiographic detection of nuclei containing the enzyme offers a new tool for the study of tumor cytokinetics.

Autoradiographic detection of dna polymerase containing nuclei in sarcoma 180 ascites cells.

Summary C3HBA mammary tumors were irradiated with 3000 rads of 250-kVp X-rays or 1000 rads of 8-MeV neutrons, doses of radiation matched for producing equal growth delay. At 14 days postirradiation, tumors were regrowing at a reduced rate relative to controls. Cell kinetic parameters were examined using percentage of labeled mitoses techniques, and blood vessel spacing and tumor architecture were examined histologically to determine whether the mechanisms underlying growth rate changes were the same after neutron as after photon irradiation. The tumor volume-doubling time at 14 days posttreatment is similar in both irradiated groups ( T d = 117 hr for neutron-irradiated tumors, 132 hr for X-irradiated tumors) and is approximately twice as long as the doubling time of 61.4 hr in control tumors in the same size range. Control and X-irradiated tumors have median cell cycle durations of 19.3 and 18.5 hr, respectively; the more slowly growing X-irradiated tumors have a reduced growth fraction and increased cell loss factor. Regrowing neutron-irradiated tumors have a median cell cycle of 27.2 hr, with calculated growth fraction and cell loss factor values intermediate between those for control and X-irradiated tumors. Scatter in the percentage of labeled mitoses data makes it difficult to determine whether the cell cycle durations are significantly different. The average distance from tumor parenchymal interphase cells to the nearest recognizable blood vessel is nearly identical in the two irradiated groups and for both groups is significantly greater than interphase to vessel distance in controls. The average distance in irradiated tumors approaches the maximal distance for O 2 diffusion in mouse adenocarcinomas of a corded structure surrounding a central blood vessel. Both neutron- and X-irradiated tumors contain more necrosis and fewer viable-appearing parenchymal cells than do control tumors of the same size. The similar growth rate and growth delay in this tumor after 3000 rads of X-rays or 1000 rads of neutrons occur in the face of possibly different cell cycle durations and seem related to similar circulatory system inadequacies which limit growth and are expressed as greater average cell-to-blood-vessel distance and increased cell loss leading to necrosis, indicating oxygen or nutrient deprivation.

https://cancerres.aacrjournals.org/content/canres/36/2_Part_1/524.full.pdf

Mechanisms Underlying Reduced Growth Rate in C3HBA Mammary Adenocarcinomas Recurring after Single Doses of X-rays or Fast Neutrons

The cytokinetics of the S-180 mouse ascites tumor system was determined on Days 2, 4, 6 and 9 of growth. Studies included volume tumor growth, per cent labeled mitoses curves, and repeated injections of tritiated thymidine. It was possible to extrapolate the cytokinetic compartment values to Day 0 of growth. Results indicate that the growth fraction of the S-180 system remains close to 1 throughout its growth, with progressive lengthening of G1, S and G2 times. Cell loss is minimal through 6 days but becomes significant thereafter. A theoretical growth curve constructed from cytokinetic values is similar to the actual volume growth curve.

Janet S. R. Nelson

Papers

Estimation of tumor growth fraction in murine tumors by the primer-available DNA-dependent DNA polymerase assay.

Autoradiographic detection of dna polymerase containing nuclei in sarcoma 180 ascites cells.

Mechanisms Underlying Reduced Growth Rate in C3HBA Mammary Adenocarcinomas Recurring after Single Doses of X-rays or Fast Neutrons

Cytokinetics of the S-180 ascites tumor system.

Cycling Characteristics of Human Lymphocytes In Vitro