Evidence of particle-associated RNA-directed DNA polymerase and high molecular weight RNA in human gastrointestinal and lung malignancies

Selected Milestones in Antiviral Drug Development

This review article will describe the (wide) variety of approaches that I envisaged to develop a specific therapy for viral infections: (i) interferon and its inducers, (ii) HSV, VZV and CMV inhibitors, (iii) NRTIs (nucleoside reverse transcriptase inhibitors), NtRTIs (nucleotide reverse transcriptase inhibitors) and NNRTIs (non-nucleoside reverse transcriptase inhibitors) as HIV inhibitors, (iv) NtRTIs as HBV inhibitors, and finally, (v) the transition of an HIV inhibitor to a stem cell mobilizer, as exemplified by AMD-3100 (Mozobil®).

Molecular evidence of viral-like biochemical activities in human genitourinary malignancies

We have demonstrated previously that core structures of urine samples from patients with genitourinary malignancies contain ribonucleic acid-directed deoxyribonucleic acid polymerase and a high molecular weight ribonucleic acid. If these particles originated from the existing genitourinary malignancies then the malignancies should contain similar characteristics. We examined 13 prostatic carcinomas, 4 bladder carcinomas, 1 urethral carcinoma and 1 hypernephroma. Positive reactions were noted in 10 of the 13 prostatic carcinomas (77 per cent), all 4 bladder carcinomas, the 1 urethral carcinoma and the hypernephroma with the simultaneous detection assay. The control samples consisted of 7 tissues of benign prostatic hypertrophy, and tissue from 2 normal bladders and 1 normal kidney. None of these tissues showed a positive response. Tritium labeled deoxyribonucleic acid probes synthesized from the malignant tissues hybridized to the polysomal ribonucleic acids but not to the corresponding normal tissues. Particles derived from the probes have a density of 1,1620 in sucrose gradient. No sequence homology could be demonstrated with various known oncogenic ribonucleic acid viruses nor with malignancies arising from other organs.

Tumor-specific DNA sequences in human gliomas

Utilizing the technique of hydroxyapatite chromatography, normal cellular DNAs were used to recycle off the repeat or normal sequences found in [3H]DNA copied off 70S RNA from malignant astrocytomas. The recycled [3H]DNA were then used to hybridize against DNAs from normal human brain tissues and DNAs from malignant astrocytomas or Grade IV astrocytomas. The results indicated the presence of tumor-specific DNA sequences in malignant astrocytomas, absent in normal brain tissues. The percentages were 88% and 7%, respectively. When recycled medulloblastoma 70S[3H]DNA probes were utilized against DNA'S FROM Grade IV astrocytomas and from normal brain, similar results were obtained. The respective percentages of hybridization were 67% and 7%. Thus it would appear that malignant gliomas contain tumor-specific DNA sequences which are not found in normal brain tissues.

Particles from mouse melanoma B16 containing reverse transcriptase and 70S RNA related to human melanoma cytoplasmic RNA

The mouse melanoma B16 contains particles encapsulating high molecular weight RNA of 60--70S size associated with a reverse transcriptase. The [3H]DNA synthesized by these particles possesses homology with RNA isolated from a hamster melanoma and from three human malignant melanomas.

Biochemical evidence for viral-like characteristics in cerebrospinal fluids of brain tumor patients

Previous work done in this laboratory has shown that human Central Nervous System tumors possess attributes in common with those found in RNA tumor viruses. Because of the intimate physical relationship between the circulating cerebro-spinal fluid and the Central Nervous System, particles derived from tumors in this system may very well be shedded into the surrounding fluid system thus displaying similar biochemical attributes. Twenty samples of cerebro-spinal fluids were examined. Fifteen were from patients with various types of tumors in various location of the Central Nervous System. Five were from patients with unrelated diseases. Eleven or 74% of those from tumor patients were found to be positive when simultaneous detection assays were done on their core structures. None of the control was positive. The [3H]DNA synthesized from core structures hybridized readily to polysomal RNAs from a solid tumor. Particles from them were found to have a density of 1.867 g/ml sucrose gradient.

Oncornaviruslike particles in human malignancies

Mesenchymal and epithelial human malignancies were examined in the simultaneous detection test for the presence of particles with 70 S RNA and reverse transcriptase. Out of the 23 tumors tested 14 were found to be positive (61%). The finding that 2 uterine cancers contained 70 S RNA and reverse transcriptase indicates that uterine cancers may belong to the list of malignancies where the involvement of oncornaviruses is suspected. Out of the 10 human sarcomas examined in this study 4 were shown to contain particles with properties of oncornaviruses.

Molecular evidence for a viral etiology of human CNS tumors

The newer methods of molecular virology, including molecular hybridization and the "simultaneous detection test," were used to examine human brain tumors for evidence of RNA tumor viruses. It was found that they contained 70S RNA and RNA-directed DNA polymerase, both encapsulated in a particle possessing a density of 1.17 g/ml. These particles therefore satisfy the three diagnostic features that characterize the animal RNA tumor viruses. Of 26 of the most malignant (glioblastoma and medullo blastoma) brain tumors examined, 24 (92%) contained these virus-like entities. The possible usefulness of these particles as aids in diagnosis and monitoring therapy is briefly discussed.

Reverse transcriptase in leukocytes of leukemic patients in remission

A cytoplasmic particulate fraction from human leukemic cells has been shown to contain reverse transcriptase and its associated high-molecular weight RHA template. We attempted to detect the reverse-transcriptase-template complex in morphologically normal peripheral blood leukocytes from patients with acute leukemia in complete remission. Our assay system consisted of a velocity glycerol gradient and cesium sulfate equilibrium gradient analysis of the endogenous reverse transcriptase reaction product. Three of nine patients in remission had positive reactions determined by glycerol gradient analysis, and eight of 10 patients in remission had positive reactions by cesium sulfate gradient analysis. We were unable to detect the template complex in leukocytes of normal persons. Thus, normal-appearing leukocytes in the peripheral blood of some leukemia patients in remission seem to retain a number of biochemical characteristics, possibly viral related, associated with leukemic cells.

Purification of RNA-instructed DNA polymerase from human leukemic spleens

Particles possessing a density of 1.16 g/ml and encapsulating a 70S RNA and a RNA-instructed DNA polymerase (reverse transcriptase) have been prepared from the spleen of a patient with chronic lymphocytic leukemia. These particles have been converted to cores with a density of 1.26 g/ml and containing the enzyme-RNA complex, in complete analogy to the known RNA tumor viruses of avian and murine origin. The reverse transcriptase was purified from the cores by column chromatography to a stage showing a single major protein band of 70,000 daltons in a gel electrophoresis. The enzyme was capable of transcribing heteropolymeric RNA into DNA complements as demonstrated by specific back hybridization to template RNA. The leukemic spleen would appear to represent an important source of this enzyme, as well as other potentially important leukemia-specific reagents.

Oncornavirus-like particles in human skin cancers

A high-molecular-weight RNA encapsulated with an RNA-instructed DNA polymerase in particles possessing the density characteristic of the RNA tumor viruses has been detected in 13 out of 14 human malignant melanomas. The [3H]DNA synthesized by these particles in an endogenous reaction hybridizes to RNA extracted from the human melanoma particulate structures, but not to RNA from normal skin. Similar particles containing RNA and enzyme have been found in basal cell and squamous cell carcinomas of the skin. The RNA of the melanoma particles is easily distinguishable by hybridization from the RNAs found in the particles of the basal and squamous cell carcinomas.