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Praetherapeutic sensitivity tests of human solid tumours based on incorporation studies of nucleic acid precursors have been described by various authors. This review intends to show that such tests may only be of rather limited value for the design of individual chemotherapeutic regimens. In many drugs, a correlation between biochemical and clinical effects has not yet been established. The reliability of praetherapeutic sensitivity tests is further impaired by general methodological difficulties of short-term cultures, individual pharmacology and toxicology of cytostatic agents as well as pharmacological and biochemical drug interactions in combination chemotherapy. Praetherapeutic testing with individual cytostatic drugs is discussed.

Acridine dyes inhibit the incorporation of 3H-thymidine and 3H-uridine in intact cells to the same extent as Actinomycin D. In contrast to Actinomycin D, RNA synthesis by DNA - dependent RNA polymerase in a cell-free system is inhibited at lo2 higher concentrations of acridine dyes, only. Possible differential effects on the cell membrane resulting in decreased intracellular pools of uridine and thymidine are discussed.

The utility of 4-hydro-peroxy-cyclophosphamide for testing the selectivity of human tumours cells against cyclophosphamide in vitro was studied. 4-hydro-peroxy-cyclophosphamide in aqueous solution spontaneously decomposes to 4-hydroxy-cyclophosphamide, the primary product of metabolic activation of cyclophosphamide thus representing a new form of "activated" cyclophosphamide. From 31 human tumours including 21 mammarian-, 4 ovarial-, 2 uterine-carcinomas, 2 seminomas, 1 hypernephroma and 1 rectum-carcinoma cell suspensions were made and the effect on the 3H-Uridine- and the 3H-Thymidine-incorporation into the nucleic acids after short time incubation with the effect of 4-hydro-peroxy-cyclophosphamide and 4-hydroxy-cyclophosphamide. 7 malignomas showed high sensitivity both against 4-hydro-peroxy-cyclophosphamide and against 4-hydroxy-cyclophosphamide. No additional inhibitory effect of the peroxyde function besides of that of the alkylating moiety of the molecule was found. Accordingly 4-hydro-peroxy-cyclophosphamide because of its better availibility and stability may be used as "activated" cyclophosphamide in screening tests for cyclophosphamide-sensivity of human tumours in vitro.

A new in vitro assay for screening the sensitivity of human tumour cells against Cyclophosphamide has been developed. While biologically activated Cyclophosphamide was unsuitable because of unpurities in the material, synthetic 4-Hydroxycyclophosphamide was shown to inhibit the incorporation of tritiated uridine and thymidine into the nucleic acids of human tumour cells in vitro. 29 tumours including 14 mammarial carcinomas, 8 ovarial carcinomas and 7 other malignant tumours were tested. While 12 tumours showed a significant and 5 only a slight inhibition of the 3H-uridine incorporation in vitro. 12 tumours showed no effect. Histologically none-differentiated tumours were more sensitive against 4-Hydroxycyclophosphamide as compared with the more differentiated ones. First observations point to 4-Hydroperoxycyclophosphamide instead of 4-Hydroxycyclophosphamide as a more suitable form of activated Cyclophosphamid for the in vitro assay of Cyclophosphamide sensitiveness because of the higher stability and better availability of this compound.

The evaluation of the nuclear morphology for the diagnostic cytology of the various types of goiters with special regard to thyroid malignancy was studied. The material for the light microscopy was obtained from the goiters by means of aspiration biopsy with thin needle and that for electrone microscopy from the excision at the operation. Both the patterns of the nucleoli were compared. The nucleolus of the thyroid cell, like in other cells, is a marker of the RNA synthetic activity. Secondary it signals the intensity of the proteosynthetic activity, that means of secretory or proliferative processes. In thyroid cells, the increased activity has a different nucleolar pattern. For that reason the study of the nucleoli is very useful in differential diagnosis of thyroid malignancy. The cytochemical examination of the nucleoli by means of toluidine blue staining is in accord with the electron microscopic pattern, where the mutual relation of the fibrillar and granular components of RNA can be evaluated.

On the basis of results showing that the extent and direction of protein biosynthesis essential for cell growth and cell differentiation can be regulated, aside from the transcription level, also on the level of ribosomes (translation), the main results of various properties of ribosomes from normal and tumor tissues are described. The main established difference between the two tissues concerns the organization and localization of the ribosomes within the cell. In tumors, polysomes and inactive dimers and monomeric particles are encountered in considerable amounts freely in the cytosol, i.e. not attached to the membranes. Furthermore, the polysomal profile of tumor cells compared with the normal tissue is characterized by a shift towards fractions with lower sedimentation coefficients. Monomeric ribosomes were not found to differ in physical and chemical properties. In smaller oligonucleotide fragments of ribosomal RNA, differences in the frequency of certain dinucleotides appear likely. Hybridization-competition experiments with DNA do suggest, however, that the ribosomal RNA from tumors is being synthesized at the same cistrons as ribosomal RNA from normal tissues, thus proving its overall sequence homology. Electrophoretic and immunologic methods have not so far revealed any clear differences in the properties of ribosomal proteins from normal and tumor tissues. In in-vitro systems, ribosomes from various tumors show approximately the same incorporation rates for amino acids as ribosomes from normal tissues. The enhanced protein synthesis of the cells, on the basis of data obtained from in-vitro experiments with cell free systems, is to be attributed mainly to the increased content of translation factors in the cytosol.

Lymphoblastoid cells were subjected to Western Blot analysis for detection of Interferon-alpha-binding proteins. JOK-1 cells--a human hairy cell leukemia line--revealed three proteins with apparent molecular weights of 120, 100 and 32 kD, respectively. Down-regulation of the receptor was observed. A differential binding pattern of two proteins (100 and 85 kD) was observed in T-CLL, whereas no signal detection was achieved in B-CLL. Mononuclear cells from 6 patients with hairy cell leukemia and 6 patients with CLL were found to differ significantly in terms of nucleic acid precursor incorporation.

An in vitro short term incubation of human tumors with different cytostatic agents and their corresponding radioactive precursors of cell metabolism allows detection of those drugs which are inefficacious on the examined tumor. The pretherapeutical knowledge of those substances keeps the patient from unnecessary and damaging cytotoxic treatment. The in vitro and in vivo correlation of this technique was tested on 3 different groups of tumor patients: 1. Chemotherapeutically treated tumor patients with primary or secondary induced resistance against the applied cytostatic agents: all substances which clinically did not influence the tumor growth at the moment of the test also were inefficient in the in vitro test system. 2. Tumor patients who were treated according to a clinical therapy regimen contrary to the results of the in vitro testing: corresponding to the test, no influence on tumor growth was seen. 3. Tumor patients who were treated according to the results of the resistance test: after 8 weeks observation none of these patients had any signs of tumor progression.

Etoposide is a semisynthetic podophyllotoxin derivative with a broad spectrum of antitumor activity and a relatively high therapeutic index. The synergism in animal with cis-platinum, cyclophosphamide, BCNU, and cytosinarabinoside is interesting for combination regimen. Mechanisms of action are inhibition of nucleoside transfer and of DNA and RNA synthesis, single stranded breaks, inhibition of protein synthesis and of microtubular assembly. While in lower concentrations etoposide is acting cell-cycle-dependent with accumulation of cells in the G2-phase it has, in high concentrations, also a cellcycle-phase-unspecific lethal effect. Most suitable is the oral and i.v. application of etoposide in fractionated doses of 80--120 mg/m2 on 3--5 consecutive days and repetition after 21 [14--28] days. Side effects are dose-limiting bone marrow toxicity, nausea, vomiting, fever, hypotension, phlebitis, mucositis, neuropathy, cardiotoxicity, alopecia. Etoposide is one of the most active single agents in small-cell bronchus carcinoma with a remission rate of 37% (10% CR), and is very active in NHL (36%), testicular carcinoma (37%), AMML (35%), choriocarcinoma (35%), and neuroblastoma (29%). The role of etoposide in combination with other active drugs in these tumors is currently investigated in bronchus and testicular carcinoma and NHL, where etoposide will belong to the drugs of the first choice in the future.

Influence of Benzenecarboxylic Acids, Particularly Mellitic Acid, on Biological in vitro Systems. In a first part of the present paper influences of mellitic acid and some other benzenecarboxylic acids on reduplication of Ehrlich ascites tumor cells cultured in vitro are reported. Mellitic acid in the concentration range between 1 and 5 mmol/l caused an increase, in concentrations of 10 mmol/l and above an inhibition of cell multiplication. Benzoic acid, phthalic acid, hemimellitic acid and pyromellitic acid showed in concentrations above 6 to 10 mmol/l inhibitory effects on cell multiplication. The second part reports studies on potential influences of mellitic acid on growth and mesenchymal metabolism of explanted murine fetal tibiae cultured in vitro for six days. Mellitic acid effected in concentrations between 0.5 and 15 mmol/l as compared with control cultures a concentration dependent inhibition of calcification and in concentrations above 2 mmol/l significant increases of the glycosaminoglycan content and growth of the explants, whereas DNA-, total protein- and hydroxyprolin content were not significantly influenced by concentrations up to 10 mmol/l.

On the basis of animal experiments it is shown that the results of tumor chemotherapy can be predicted with the aid of in-vitro test systems. In investigations carried out on human tumors, the correlations obtained between in-vitro test results and response to therapy are promising. However, definitive proof of a correlation can only be provided by planned, statistically supported clinical studies. Two types of information can already be obtained from the in-vitro tests: data concerning the rate of proliferation of the tumor, on which the activity of cytostatic agents depends, and data on certain types of resistance to cytostatics.

When incubated for 30 min in vitro, 4-hydroxyalkenals in a 5 x 10-3 M solution react with SH-groups of soluble cytoplasmic and nuclear proteins (ProtL-SH) of Morris hepatomas 9618 A and 5123 tc, and of Ehrlich ascites tumor (EAT) cells. The extent of the reaction strongly increases with decreasing doubling time of the respective tumors. Former experiments with EAT cells have shown that the reaction with cytoplasmic ProtL-SH causes inhibition of respiration, glycolysis, and probably of other SH-controlled processes associated with cell division. The intranuclear reaction leads to an inhibition of DNA- and RNA-synthesis. In a 2 x 10-4 M solution of hydroxyalkenals, however, the reaction with cytoplasmic ProtL-SH diminishes almost completely so that no measurable inhibition of respiration and only 3% inhibition of glycolysis are observed, while 20 to 30 percent of the nuclear ProtL-SH are still blocked. This corresponds well with a previous observation that a 2 x 10-4 M solution of hydroxypentenal inhibits DNA-synthesis by 90 percent.

The activity of Mg2+-activated enzymes shows a bell shaped pMg dependency, with a pMg optimum at 3. Intracellular Mg2+ concentrations, determined by different methods, are about 10(-3) mol/1. Thus Mg2+-dependent enzymes are optimally activated, or nearly so, with Mg2+. If the substrates of an enzyme form complexes with Mg2+ of different stabilities, and if free substrate and the substrate-Mg2+ complex react differently with the enzyme, the equilibrium will change with the concentration of Mg2+. When the extracellular concentration of Mg2+ is increased, Mg2+ becomes bound practically exclusively to the cell membrane. In Mg2+ deficiency, the intracellular concentrations of Na+, K+, Ca2+ and cycl. AMP are changed, and the rates of synthesis of DNA, RNA and protein are decreased.

N-Methyl-N-beta-chloroethyl-hydrazine and its bezaldehydhydrazone inhibit the synthesis of DNA and RNA in ascites cells in vitro faster and stronger than N,N-Dimethylhydrazine and procarbazina does. The benzaldehydhydrzone essentially inhibits influx and phosphorylation of nucleosides whereas N-Methyl-N-beta-chloroethylhydrazine acts directly on DNA synthesis.