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In the opinion of the authors, good medical practice demands the avoidance of ineffective therapies and good cancer chemotherapy generally demands the avoidance of inactive drugs. The authors present their viewpoint that randomized trials are not required to prove that physicians should not administer inactive drugs and that existing cell culture assays are acceptably accurate in identifying inactive drugs. They describe and advocate the use of two such tests to aid in choosing between different forms of therapy that would otherwise be equally acceptable in the absence of test information. Strengths, weaknesses, and applications of the assays are discussed.

Xenogeneic immune RNA (I-RNA), extracted from the lymphoid organs of sheep or guinea pigs immunized with human tumor cells, mediated in vitro cytotoxic immune responses that were directed specifically against tumor-associated antigens of human tumor target cells. Normal human peripheral blood lymphocytes from healthy donors became markedly more cytotoxic for human tumor target cells after being incubated with I-RNA extracted from the lymphoid organs of animals that had been immunized with that particular tumor. Gastric carcinoma, malignant melanoma, and carcinoma of the breast were studied. Lymphocytes incubated with RNA from animals immunized with only complete Freund's adjuvant evidenced no increased cytotoxic activity. RNA extracted from the lymphoid organs of animals immunized with normal skin fibroblasts that were autologous to the immunizing tumor, when incubated with normal allogeneic lymphocytes, also mediated cytotoxic immune reactions against tumor target cells. These immune responses probably were directed principally against normal transplantation antigens. However, when lymphocytes that were autologous to the immunizing tumor and/or the tumor target cells were incubated with RNA from animals immunized with autologous normal fibroblasts, cytotoxicity did not increase. Only I-RNA extracted from donor animals specifically immunized with tumor cells mediated cytotoxic antitumor immune responses when incubated with autologous lymphocytes.

The immunologic effects of leukapheresis on cancer patients and three other groups of donors using the continuous-flow blood cell separator are presented according to the protocol described in the preceding article. Transient declines were noted in per cent T-lymphocytes of some, but not all, leukapheresed normal donors and cancer patients. These declines were comparable to the small declines observed in sham donors and the fluctuations in per cent T-lymphocytes noted in individuals who did not undergo leukapheresis. There were no changes in lymphocyte-mediated cytotoxicity to a melanoma cell line in 2 of 4 melanoma patients, while values in 2 patients fell by about one-half within 4 hours and returned to preleukapheresis levels by 24 hours. Release of macrophage migration inhibition factor by lymphocytes from all 4 cancer patients and 4 normal donors, in whom this parameter was studied, fell transiently and returned to preleukaphresis levels within 24 hours. Blastogenic responses of lymphocytes from cancer patients and normal donors to phytohemagglutinin (PHA) and in one way mixed lymphocyte reactions increased in several individuals and decreased slightly in others. There appears to be no significant immunosuppressive effects (within the parameters studied) of a single leukapheresis for lymphocytes on the blood cell separator, since changes in lymphocyte parameters were relatively minor, transient, and variable and, where studied, paralleled fluctuations observed in sham donors and individuals not undergoing leukapheresis.

Simple methods were developed for cloning human solid tumors; 68 percent of the tumors processed formed at least 30 colonies within two to four weeks. The accuracy of the clonogenic assay for predicting clinical response was determined in a prospective, correlative study. Eight-four patients had objectively measurable disease and had at least one course of chemotherapy. Tumor types included melanoma (33), lung (12), colon (7), breast (7), stomach (4), ovarian (12), sarcoma (7), and hepatoma (2). For patients whose tumors were sensitive in vitro to a particular drug, clinical response was seen in 21/25 cases (84 percent). Tumor resistance was found in 59 instances, and 54 patients (92 percent) had no clinical response to the same drugs. Associations between in vitro chemosensitivities and clinical course were highly significant.

A rapid assay for in vitro chemosensitivity testing measuring [3H]thymidine incorporation has been developed. Results of this assay correlate highly with chemosensitivities determined by the soft-agar clonogenic assay. A correlative study was carried out on 219 solid tumor specimens to assess the ability of the rapid assay to predict clinical response to antineoplastic therapy. One hundred forty-two of 219 tumors (65%) yielded chemosensitivity data. Of these, 33 were evaluable for in vitro-in vivo correlations. In vitro sensitivity (greater than or equal to 80% inhibition of thymidine uptake) was associated with clinical response in 6 of 13 patients. In vitro resistance was associated with progressive disease in 20 of 20 patients. The rapid assay offers several advantages over the soft-agar clonogenic assay, including higher success rate, avoidance of clumping artifact, shorter time course (5 days), and very low false-negative rate. Further refinement may be necessary, but the rapid assay appears to have potential for individualizing solid tumor chemotherapy.

A phase I clinical trial of immunotherapy with "Immune" RNA was undertaken fifteen months ago. Twenty-six cancer patients were treated with RNA extracted from the lymphoid organs of sheep immunized with either autologous tumor cells or allogeneic tumor cells of the same histologic type. Eighteen patients had gross disease and eight had minimum residual disease. RNA was administered weekly, intradermally, at doses up to 9 mg/week without any significant local or systemic toxicity. Four patients improved, thirteen achieved stability of disease or possible improvement, seven were treatment failures, and two are indeterminate. Lymphocyte-mediated cytotoxicity to allogeneic tumor target cells of the same histologic type were monitored in eleven patients. In seven patients, cytotoxicity increased after "Immune" RNA therapy; no change was observed in three patients; a decrease was noted in one patient. There appeared to be a possible correlation between cytotoxicity assessed in vitro and clinical response. There is some evidence that these responses may be specific for the particular tumor used to immunize the RNA donor.

Two technological problems limit the usefulness of chemosensitivity assays: low success rates (generally 30-60%); and the requirement for large numbers of tumor cells (5 X 10(5)/dish). To solve these problems, we developed a miniaturized, improved, nucleic acid precursor incorporation assay (MINI-assay). In this new assay, 0.3-1.5 X 10(5) tumor cells were plated in double-layer agarose in 16-mm wells of a Costar (No. 3524) 24-well cluster dish. After 72 h of incubation, 5 microCi [3H]thymidine were added to each well. After an additional 24 h of incubation, the trichloroacetic acid-precipitable material was collected and counted by liquid scintillation. We found that 280 of 351 (80%) human solid tumors gave evaluable chemosensitivity results. Labeling efficiency was optimum when the plating density was between 1.5 and 3 X 10(4) cells/well. Radioisotope uptake was less efficient in 35-mm Petri dishes and in the 7-mm wells. The MINI-assay was particularly suitable for small specimens (less than 1 g) and for tumor types that usually yield small numbers of viable tumor cells (19 of 30 breast cancers and 56 of 71 sarcomas were evaluable). The artifacts of colony counting (cell clumps, debris, clots) were also eliminated with this assay. With high evaluability rates, the requirement of fewer cells, a short duration (5 days), and ease of quantitation, the MINI-assay is widely applicable to chemosensitivity testing in human tumors.

An improved method for testing human tumors against chemotherapeutic agents was developed. Drug effects were quantitated in the thymidine incorporation assay (TIA) by measuring inhibition of deoxyribonucleic acid (DNA) synthesis by the proliferating cell population following exposure to anticancer drugs. Results were obtained within five days. A total of 480 out of 568 tumors received were evaluable for an overall growth rate of 85 percent. Even small biopsy specimens could be successfully grown. In 126 correlations with clinical response, the TIA had a prediction accuracy for sensitivity of 51 percent and a prediction accuracy for resistance of 97 percent. Because it is rapid, has a high growth rate, and is not subject to clumping and other cellular artifacts, the TIA represents a significant improvement over colony counting assays for predicting drug effects in human tumors.

Allogeneic immune RNA (I-RNA), extracted from the peripheral blood lymphocytes of patients putatively cured of cancer, mediated cytotoxic immune reactions that apparently were directed specifically against human tumor-associated antigens. I-RNA was extracted from the peripheral blood lymphocytes of patients with various types of cancer. Patients selected had not been previously sensitized to HL-A or other normal transplantation antigens or to blood group antigens. Normal human peripheral blood lymphocytes were incubated with these allogeneic I-RNA preparations and tested for cytotoxicity against human target cells in vitro. Allogeneic I-RNA mediated cytotoxic immune reactions only against tumor target cells of the same histologic type as the I-RNA donor. I-RNA's extracted from peripheral blood lymphocytes of melanoma patients mediated cytotoxic immune reactions only against melanoma cells. Similarly, only I-RNA's extracted from the lymphocytes of patients with colon cancer mediated cytotoxic immune reactions against colon carcinoma cells, and only I-RNA's from the lymphocytes of breast cancer patients mediated immune reactions against breast cancer target cells. Allogeneic I-RNA extracted from peripheral blood lymphocytes of cancer patients possibly mediated specific cytotoxic immune reactions that were directed against common tumor-associated antigens shared by human tumors of similar histologic type.

The human tumor colony-forming assay was used to compare chemosensitivity among tumor cells within a primary tumor, between primary tumor and metastases, and between different metastases. No significant differences in cloning efficiency were found in any of the three comparison studies. However, considerable differences in chemosensitivities were observed between different parts of the same tumor and between the primary tumor and metastases. Two different parts of the same tumor were comparably assayed for nine primary tumors. In nine paired samples which allowed in vitro drug sensitivity testing, there was no satisfactory correlation of sensitivity to cytostatic drugs. Cell suspensions were prepared from 28 primary tumors and from metastases taken from the same patient. In 14 paired samples which formed sufficient colonies for determination of drug effect, the data showed no satisfactory correlation of chemosensitivity between a primary tumor and its metastases. Both tumor samples from different metastatic sites of the same patient formed sufficient colonies in seven of eight instances. In the seven paired samples, there was strong association of chemosensitivity (p less than 0.005). The results indicate that the reported discrepancies of in vitro and in vivo results in clinical trials using the tumor colony-forming assay for predicting resistance or sensitivity to cytostatic drugs may be due to therapeutic heterogeneity among tumor colony-forming units within a primary tumor and between a primary tumor and its metastases.

Ribonucleic acids extracted from specifically sensitized lymphoid cells (I-RNA) have been shown to transfer specific immunoreactivity to normal non-immune lymphoid cells. Evidence for the transfer by I-RNA, of immune responses to tumor-associated antigens of animal and human neoplasms, in vivo and in vitro, is reviewed. Results obtained in our laboratory and in other laboratories indicate that xenogeneic, allogeneic and syngeneic I-RNA extracts mediate specific cytotoxicity to tumor cells, in vitro, and mediate transplantation resistance and tumor rejection responses in vivo. Our results suggest that I-RNA preparations fail to elicit immune responses directed against "self" antigens. By contrast, I-RNA's directed against "non-self" tumor-associated antigens appear to induce lymphocytes to effect specific anti-tumor immune responses. The mechanisms responsible for the failure of I-RNA to initiate immune responses against "self" antigens are not known at present and demand investigation. Preliminary results of a clinical Phase I trial of immunotherapy with xenogeneic I-RNA in selected cancer patients are reviewed. I-RNA might offer promise as a new modality for the immunotherapy of human cancer.

The clinical usefulness of the soft agar colony-formation assay of in vitro chemosensitivity developed by Hamburger and Salmon is limited by long turnaround time (2-3 weeks), low success rate for small specimens, and clumping artifacts that can lead to erroneous predictions of resistance (false-negative errors). An improved technique was developed for measuring in vitro growth by incorporation of tritiated thymidine that can be performed in 5 days. With this rapid assay, 819 tumors were processed, with an overall success rate of 59.3%. This result compared favorably to the overall success rate of 58.2% for 1591 colony-formation assays because more small specimens could be submitted for the rapid assay. Melanoma and ovarian cancer specimens grew particularly well (76% and 75% successful, respectfully). Sixty-five correlations of in vitro and in vivo responses are available to date. None of 30 tumors, predicted to be resistant in vitro responded to chemotherapy clinically. Patients whose tumors were predicted to be sensitive in vitro had a 43% clinical response rate. The assay appears to be particularly accurate for predicting clinical resistance to chemotherapy, possibly because clumping artifacts do not occur in this system and peak achievable plasma concentrations of chemotherapeutic agents can be used. Optimal in vitro drug concentrations and culture conditions are still being defined, and improved success rates are being seen with more recent specimens. The introduction of this technique underscores the fact that in vitro chemosensitivity tests must continuously evolve to maximize their clinical application.