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A large series of samples obtained after surgical resection of intestinal mucosa of patients affected by intestinal carcinoma was examined in order to define possible relationships between levels of enzymes involved in the purine salvage pathway and clinical/biological parameters of aggressiveness and invasiveness. The results confirm our previous observation on a different pattern of purine salvage enzymes in tumor as compared to normal colon tissues (Camici et al., 1990). In fact, we observed in human colon tumor tissues a significant enhancement of the three enzymes involved in the synthesis of IMP, hypoxanthine guanine phosphoribosyltransferase (HGPRT), adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP). On the other hand, no variation was observed in the 5'-nucleotidase and alkaline phosphatase activities. While we could not find a significant correlation between HGPRT, ADA and PNP activities and histologic grading or biological parameters of tumor aggressiveness, the significant correlation with the extent of disease, as expressed by the Dukes' stage, would demonstrate at least for human colon tumors, a relationship between enzyme activity and tumor invasiveness.

The in vitro activity of elsamicin A (ELS) was investigated compared with that of doxorubicin (DX) on two sensitive breast cancer cell lines: one estrogen receptor-positive (ER+, MCF7) and one estrogen receptor-negative (ER-, MDA-MB-231) line, and on a DX-resistant subline (MCF7DX). The activity of the two drugs was also investigated on 19 clinical breast cancer specimens from untreated patients. The drugs were tested at pharamcologically relevant concentrations, as calculated from the area under the curve for a 3 h exposure to the lethal dose producing 10% mortality (LD10) in mice, and at 10- and 100-fold concentrations. In DX-sensitive lines, a greater inhibition of RNA and DNA precursor incorporation, as well as of cell proliferation, was caused by ELS than by DX. Moreover, the antiproliferative effect was 10-fold higher in the ER+ MCF7 than in the ER- MDA-MB-231 cell line (IC50: 0.25 versus 0.21 micrograms/ml). ELS was cross-resistant to DX in the MCF7DX subline. In clinical specimens, effects on DNA precursor incorporation were more often observed for ELS than for DX at the same drug concentrations. The in vitro sensitivity to ELS was more pronounced for ER+ than for ER- tumors: minimal inhibiting concentrations of the drug were 0.1 and 3.5 micrograms/ml, respectively, in the two groups. If confirmed in a larger series of human breast tumors, these in vitro results would indicate a promising role for ELS in clinical treatment, mainly of ER+ breast cancer patients.

Expression of P-glycoprotein was evaluated by C219 monoclonal antibody immunoblots in 34 previously untreated and 14 pretreated breast cancers and in benign breast lesions or histologically normal breast glands. P-glycoprotein was not detectable in the few cases of normal or benign tissue. P-glycoprotein was expressed in the 170 kD areas of 29% (10/34) of untreated and 64% (9/14) of previously treated tumours (P = 0.02). In treated tumours, high intensity expression was observed more frequently than in untreated breast cancer (40% vs. 9%). Moreover, there was a significant association between P-glycoprotein expression and in vitro resistance to doxorubicin and vincristine. Simultaneous resistance was observed in all of the P-glycoprotein positive and in only 56% of the P-glycoprotein negative tissues (P less than 0.01). Some aspects of the typical multidrug resistant phenotype, such as P-glycoprotein expression and simultaneous resistance to doxorubicin and vincristine, could be detected in small subsets of breast cancer patients. No relation between P-glycoprotein expression and the type of previous clinical treatment was observed.

The in vitro cytotoxic activity of azelaic acid was studied with 25 human melanoma primary cultures and with 5 established cell lines characterized by different contents of melanotic pigment. A dose-dependent antiproliferative effect was observed in both the experimental systems, even though cell lines displayed a slightly greater susceptibility to the compound, with ID50 values generally lower than those for fresh human tumors. Our results do not demonstrate a clear difference between melanotic and non-melanotic melanomas in sensitivity to azelaic acid. The early interference of azelaic acid on nucleic acid metabolism was investigated additionally with 15 human melanoma primary cultures. There were significant inhibitions of RNA and DNA synthesis in a remarkable percentage of tumors, at the highest concentrations of the compound. Moreover, cell proliferation of tumors that showed these antimetabolic effects was always significantly depressed by lower drug concentration as well as by the highest.

The enzymatic pattern of five enzymes involved in the purine salvage pathway, namely purine nucleoside phosphorylase (EC 2.4.2.1), adenosine deaminase (EC 3.5.4.4), 5'-nucleotidase (EC 3.1.3.5), alkaline phosphatase (EC 3.1.3.1), and hypoxanthine-guanine phosphoribosyltransferase (EC 2.4.2.8) has been evaluated both in human intestinal and breast carcinomas and compared to that of normal tissues. A higher level of hypoxanthine-guanine phosphoribosyltransferase was associated with tumor tissues. This metabolic alteration should lead to an elevated synthesis of nucleotides in cancer cells, might confer selective growth advantages to neoplastic tissues, and account, at least in part, for the difficulties encountered in the chemotherapy of human tumors, by using compounds affecting only the purine de novo biosynthesis.

A short-term antimetabolic assay based upon the inhibition of incorporation of nucleic acid precursors was used to compare the cytotoxicity of a new halogenated anthracycline, 4'-iodo-4'-deoxydoxorubicin (IDX), with that of its parent compound doxorubicin (DX) on human colo-rectal carcinoma specimens. IDX showed a marked dose-dependent effect, with frequencies of activity consistently greater than those of DX at all concentrations. The minimal dose required to induce a significant antimetabolic effect for IDX was 1/10 that for DX.

A short-term antimetabolic assay, which considers the interference with [3H]thymidine incorporation as an indicator of drug effect, has been used to comparatively assess the chemosensitivity of different tumor lesions from the same patient. The analysis was performed on primary tumors and their synchronous metastases from 67 patients with breast, ovarian, gastrointestinal and germ cell testicular tumors. A remarkable difference in sensitivity to cytostatic drugs was observed between the two lesions. In contrast, a strong association in chemosensitivity (81.7% agreement rate; p less than 0.01) was observed between two synchronous metastases from 17 patients with breast, ovarian, germ cell testicular tumors or malignant melanoma. In addition, the predictive relevance of the antimetabolic assay on clinical response to chemotherapy was analyzed in relation to the type of tumor lesion tested in vitro in a retrospective correlative study on 57 patients with advanced ovarian and germ cell testicular tumors. The objective clinical response was significantly correlated to the in vitro sensitivity of metastases (83.7% agreement rate; p less than 0.01), but not to that of the primary tumor.

The stimulation of RNA synthesis induced by estradiol has been studied on 60 breast cancers in short-term cultures. In the same tumors the estrogen receptor (ER) assay was carried out. In 35% of the cases studied the stimulating effect by estradiol in vitro was observed. The frequency of response to in vitro hormone treatment was higher (42%) in ER+ cancers and lower (25%) in ER- cancers. The specificity of the in vitro test was assessed by the use of tamoxifen.

A membrane purification procedure and an immunoblotting assay have been designed to allow screening of human solid tumors for overexpression of the GP170 glycoprotein without employing a disaggregation method to obtain cell suspensions. The electrophoresed membrane proteins were probed, after Western Blotting, with the C219 monoclonal antibody and iodinated Protein A. The labeling intensity of the bands on the autoradioimmunoblots were quantified by densitometry. To test for the presence of GP170, we used membranes from the UV 2237 fibrosarcoma line and its adriamycin-resistant variant ADMR, grown in vitro or as solid tumor in mice. Membranes of human normal and tumor tissues obtained from previously untreated patients were also tested. An immunoreaction was observed in the adriamycin-resistant UV 2237 lines grown in vitro or in vivo. Quantitatively, the binding of the resistant cell line grown in vitro was higher than that observed in cells grown in mice. Bands in the GP 170 region were observed in 4/7 normal and in 7/7 tumor colon tissues and in the normal medulla from 2 patients with cancer of the renal cortex. No reaction could be found in samples from normal tissue, primary tumor or nodal metastasis from 7 patients with breast cancer.

The activity of some alkylating agents widely used in clinical practice was studied by an in vitro antimetabolic assay, which evaluates the interference of drugs on the incorporation of 3H-thymidine and 3H-uridine in short-term cultures of human tumors. The effect of CCNU, chlorambucil, cisplatin, melphalan, prednimustine, procarbazine and the pro-active derivatives of cyclophosphamide and ifosfamide, 4-hydroperoxycyclophosphamide and 4-hydroperoxyifosfamide, was tested on non-Hodgkin lymphomas, germ cell testicular tumors, breast and ovarian cancers. Similar effects were generally produced by the drugs on both DNA and RNA precursor incorporation, and the in vitro response rates were similar to those clinically obtained for the same tumor types by using the same drugs in monochemotherapy. The effects of different alkylating agents on the individual tumors were not significantly associated, except for the analogues 4-hydroperoxycyclophosphamide and 4-hydroperoxyifosfamide, for which a significant agreement rate was observed. No evidence of acquired resistance to 4-hydroperoxycyclophosphamide and cisplatin after clinical treatment with the same drug was found in samples from ovarian cancer and non-Hodgkin lymphoma, but there was a definite trend in germ cell testicular tumors to lower sensitivity to cisplatin in previously treated patients.

An in vitro chemosensitivity test is described for the quantitative determination of the interference of antitumoral drugs on nucleic acid metabolism in short-term cultures of non-Hodgkin's malignant lymphomas. Preliminary biochemical studies have defined the optimal culture conditions and have guaranteed the reliability and the reproducibility of the test. Our results for adriamycin and prednisone are in agreement with those obtained on experimental systems with other techniques.

An in vitro assay, which evaluates the effect of drugs on labelled DNA precursor incorporation into fresh specimens after 3 h of in vitro treatment, was used for a prospective study. Drugs were used as monochemotherapy or in different combinations according to their in vitro activities for salvage or palliation treatment of 16 patients with germ cell testicular tumors, for a total of 21 correlations between in vitro and clinical results. In 11 instances, drugs active in vitro were used; in 10 instances, because no drug was active in vitro, patients were treated with inactive drugs. There was a significant correlation between in vitro and clinical activity (p = 0.02), with a very high true-negative rate (90%) and a lower true-positive rate (54%). No patient treated with drugs inactive in vitro survived 2 years, whereas freedom from progression and overall survival for patients treated with drugs active in vitro were 27.3 and 36.4%, respectively (active vs. inactive, p = 0.007). The overall response in the group of patients treated prospectively was comparable to that observed in a group of 9 patients treated in the same period of time with drugs of unknown in vitro activity (33 vs. 11% objective and long-term responses, respectively, p = n.s.) notwithstanding the high percentage of patients treated with drugs inactive in vitro in the former group.