Potential and problems with growth of breast cancer in a human tumor cloning system

Simultaneous soft agar cloning of ascites and solid tumor specimens from patients with ovarian cancer

Concurrent Cloning Efficiencies (CE) of both ascites and solid tumor samples from 36 patients with ovarian carcinoma were studied using the soft agar assay. The CE of both were highly variable (range, 0-1.234% and 0-0.802%, respectively). There was marked intrapatient and interpatient heterogeneity in the CE. Of the 36 tested, comparative CE were evaluable in 29. CE was 0 in both solid tumor and ascites in one patient. CE was 0 in four other ascites samples from four patients. In other 24, the relative CE of solid tumor/ascites from each patient ranged from 0.066 to 435. In the 29 patients with samples of ascites and a solid tumor evaluable for concurrent CE, the median colony counts of solid tumors was more than tenfold higher than ascites. The solid tumors obtained from 31 patients had a significantly higher CE than tumor cells obtained from ascites samples from 32 patients. Solid tumors were significantly better than ascites for in vitro testing based on the data that 75% (27/36) of solid tumors and only 31% (11/36) of ascites formed greater than or equal to 30 colonies. The drug sensitivity profiles of tumor cells from a solid tumor and ascites of the same patient appear similar. Based on these observations, it may be more cost and labor effective to do soft agar in vitro chemotherapy assays using a solid tumor than ascites in ovarian carcinoma.

Clonogenic in vitro growth and histologic grading of primary human breast tumors

We determined the relationship of clonogenic in vitro growth and histopathologic features of 31 primary human breast tumors. Well-differentiated primary tumors formed fewer colonies than poorly differentiated tumors, and the clonogenic in vitro growth of tumors correlated inversely with patient survival. The potential of the clonogenic assay to serve as a predictor of disease course should be explored further.

The human tumor stem cell assay revisited

The human tumor stem cell assay (HTSCA) is a bilayer soft agar system for growing fresh human tumor specimens in vitro to determine drug sensitivity and improve our understanding of tumor biology. Recent clinical correlations of 60% accuracy for predicting a positive clinical response and a 90% accuracy for predicting a lack of response to therapeutic agents suggest promising clinical usefulness. However, the clinician should be aware of the assay's inherent pitfalls, such as heterogeneity of the tumor specimen, inability to obtain pure single-cell suspensions, low cloning efficiency, unusual drug dose-dependent survival curves, uncertain validity of in vitro pharmacology, non-standardized criteria for in vitro sensitivity, and the variability of in vitro results. A brief summary of the concepts, potential, and limitations of this assay are discussed.

Disaggregation of human solid tumours by combined mechanical and enzymatic methods

Two combined mechanical and enzymatic disaggregation techniques and a simple mechanical disaggregation procedure were compared. The combined procedures involved a mechanical comminution of the tumour tissue followed by incubation in trypsin. In one method, the tissue was subjected to long-term trypsinization at 4 degrees C, and in the other procedure, repeated short-term trypsinization at 37 degrees C was applied. The results were compared in terms of the yield of viable cells, plating efficiency, the ability to produce tumours in nude mice, and DNA distribution as measured by flow cytometry. The combined techniques provided reproducible cell yields of 2-10 X 10(7) viable cells g-1 of tissue, whereas only a small number of tumour cells was produced by the mechanical method. DNA analysis demonstrated that only the long-term trypsinization procedure resulted in a representative cell yield from all the tumours tested.

Selective effects of insulin and hydrocortisone on colony formation and chemosensitivity of human tumors in soft agar

Because low plating efficiencies of most human cancers severely limit the number of successful chemosensitivity tests that can be performed, we studied the growth-enhancing effects of insulin and hydrocortisone on a variety of solid tumors. Colony formation in soft agar was significantly increased in 23/49 (47%) tumors treated with 3 U/ml insulin, whereas fewer colonies were observed in 7 (14%). These effects were highly selective for tumor type. Colony growth for ovarian, lung, and colon carcinomas increased by 123%, 37% and 28%, respectively. In contrast, insulin inhibited the growth of melanoma, kidney, and breast tumors. Hydrocortisone at 0.05 microgram/ml increased colony numbers in 23/45 (51%) tumors, while in 7 (16%) colony numbers were decreased. Growth of ovarian, lung, breast, and kidney carcinomas was increased by 136%, 126%, 78% and 69%, respectively, whereas melanomas, sarcomas, and colon tumors were inhibited by hydrocortisone. In vitro chemosensitivities were relatively unchanged by the hormones. In 168 (134 paired) drug/tumor tests, sensitivity to standard antineoplastic drugs in the presence or absence of hormones was concordant 82% of the time (correlation coefficient, 0.71). However, in 20 tests (15%), significant enhancement of chemosensitivity was observed. We concluded that cloning efficiencies of many common human tumor types can be improved with hormones, and that these growth-enhancing effects are selective for tumor type.

Concentration and time-dependent inter-relationships for antitumour drug cytotoxicities against tumour cells in vitro

Cryopreserved tumour cells obtained from the ascitic fluid of a patient with an ovarian carcinoma were employed to determine the effect on in vitro drug cytotoxicities of varying both drug concentration and exposure time. Four antitumour drugs, in common clinical usage, were selected for study. Tumour-cell survival following drug treatment was measured by colony-forming ability in the soft-agar developed by Courtenay et al. (1978). Treatment with cis-platinum, adriamycin or vinblastine generated exponential survival curves with increasing cell kill resulting from either increasing drug concentrations or prolonging exposure times. In contrast, no detectable cell kill was elicited by treatment with hydroxyurea for short exposure times of 1 or 6 h, even at concentrations as high as 1 mg/ml, although continuous drug exposure resulted in a steep exponential survival curve. These results, obtained directly from biopsy material, are in close agreement with data from parallel studies employing a continuous human tumour-cell line (COLO 205 derived from a colon carcinoma). Duration of exposure is therefore an important determinant of drug-induced cytotoxicity under these assay conditions. The results with hydroxyurea, however, imply that prolonged incubation times are necessary to evaluate the cytotoxicity of certain agents and so the routinely employed 1 h exposure in most current human tumour drug sensitivity tests is inadequate for such drugs. These data therefore provide evidence that employing a single set of standard conditions of drug exposure to evaluate all antitumour drugs may be inappropriate.

Human tumour clonogenicity in agar is improved by cell-free ascites

Replacement of enriched CMRL 1066 medium by cell-free ascites from tumour patients in the human tumour clonogenic assay described by Hamburger and Salmon (1977) increased plating efficiency for ovarian cancer cells by a median of 8-fold (range 0.4-1012 fold). In 40 experiments, two cases had a lower plating efficiency when cultured in cell-free ascites, 10 grew neither in standard medium nor in cell-free ascites and in two cases, growth was only observed in cell-free ascites. With standard medium, we observed 53% growth (greater than 5 colonies/dish) and 41% evaluable for chemosensitivity testing (greater than 30 colonies/dish). With cell-free ascites as culture medium, these figures were 71% and 63%, respectively. While under standard conditions the highest plating efficiency obtained was 0.25%, in 21% of the experiments done with cell-free ascites a plating efficiency higher than 1% was reached. We conclude that cell-free ascites is able to stimulate proliferation of ovarian cancer cells in agar and that the use of it extends the applicability of the clonogenic assay.

Direct cloning of human breast cancer in soft agar culture

A human tumor cloning system has been utilized to grow human breast carcinoma. A total of 225 specimens have been placed in culture. One hundred thirty-two were from primary chest cancer specimens and 93 were from metastatic lesions. Of these, 71% of the primary breast carcinomas and 75% of metastases formed greater than or equal to 5 colonies per 500,000 cells plated. Forty-five percent of the primary breast carcinomas and 52% of the metastases formed enough colonies (greater than or equal to 30 colonies per 500,000 cells plated) to perform meaningful in vitro drug testing. Estrogen receptor status did not influence the percentage of tumors which formed colonies in vitro. Histologic and nude mouse studies provided confirmatory evidence the colonies were composed of breast cancer cells. In 176 in vitro chemotherapeutic drug tests, the anticancer agents commonly used clinically for treatment of breast cancer, i.e., Adriamycin, 5-fluorouracil, etc., showed some in vitro activity. This activity was not as dramatic as is seen in the clinic with these conventional agents. Future work should concentrate on improving the number of colonies which form from breast cancer specimens and on prospective use of the system for screening for new agents for the treatment of human breast cancer.