Can tumorigenesis result from in vivo “transfection” of a normal cell with DNA escaped from disintegrating nontransformed cells?

In this paper I present a hypothetical step on the route to turmorigenesis which may be common to many of the tumorogenic events taking place in vivo. According to this hypothesis portions of DNA from normal nontransformed dying cells may escape degradation, “transfect” other cells and under appropriate conditions also induce transformation. When various high risk factors for carcinogenesis are examined this hypothesis may easily fit into each of them. In addition, recent reports of experimental “transfection” indirectly support this hypothesis. It could now be argued that aging, ionizing radiation, immunosuppressive drugs, genetic errors, defects in DNA repair, immunodeficiency states, chronic infections and chronic inflammatory diseases may all increase the availability of free DNA or the readiness of cells to accommodate “transfection” DNA, or both. Thus the risk of cancer associated with these situations may be explained by increased chance for “transfection” with DNA.It is suggested that the minimal requirements for cell transformation consist of a certain sequence of DNA which does not have to be integrated into the nucleus at once, it may instead accumulate piece by piece so that the first “transfection” of a cell may occur long before transformation takes place. If the “transfecting” DNA sequence does not fulfil the minimal requirements for maintaining a state of repetitive uncontrolled mitosis, then this cell may wait silently or remain a benign tumor until “boosted” with an ultimate complementary DNA sequence to develop into a fully fledged cancer.     

The energetic costs of tail autotomy to reproduction in the lizard Coleonyx brevis (Sauria: Gekkonidae)

Summary Energy reserve utilization and energy budgets were compared in tailed and tailless adult female Coleonyx brevis. Carcass, fat body and caudal energy reserves were used for vitellogenesis; mass and energy content (cal/mg and/or cal/reserve) of each were significantly lower at oviposition than at the initiation of vitellogenesis. Total energy reserves accounted for 53% of the reproductive energy investment in tailed females compared to 29% in tailless females. Tailed females had over twice as many reserve calories for egg production than tailless females. Caudal energy reserves represented 60% of the total reserves of tailed females and were one-third greater than the total energy reserves of tailless females. To produce a clutch of eggs both tailed and tailless females supplemented energy reserves with net metabolizable energy that was available after metabolic costs were paid. Tailless females had a significantly greater rate of food ingestion and more net metabolizable energy available for reproduction than tailed females, yet allocated significantly fewer calories/day to reproduction than tailed females, primarily because of the loss of caudal reserves. Reproductive efforts of tailed and tailless females were equivalent. However, the loss of caudal reserves resulted in the production of eggs that were significantly lower in mass and energy content (cal/mg and cal/egg) than when caudal reserves were used. Results empirically support the hypothesis that reproduction has energetic priority over tail regeneration in short-lived, iteroparous species with a low probability of future reproductive success.     

Long-term culture of human aortas

Summary Segments of human thoracic aorta were maintained in long-term explant culture for 18 weeks in serum-supplemented medium. The aortas were grossly normal in appearance, and random samples fixed for light microscopy prior to culture revealed a normal morphology. The intima contained no more than five layers of smooth muscle cells. After 7 days in culture, the intima was noticeably thicker than the uncultured segments. The increased thickness was due to proliferating smooth muscle cells and production of extracellular material. After several months in culture, extracellular material consisting of collagen and flocculent material was present in areas resembling atherosclerotic fibrous plaques. A peripheral growth, which formed around the explant, was composed of fibroblastlike cells and added to the overall thickness of the intima. However, aortic segment maintained for up to 2 months in serum-free culture medium showed no cellular proliferation. This study demonstrates that changes resembling early stages of atherosclerosis occur in human aortas maintained in explant culture using routine culture procedures. Supported in part by the Pangborn Fund and the Graduate School of the University of Maryland. This is publication 443 from the Cellular Pathobiology Laboratory.     

The effect of ecdysterone on nonhistone proteins in salivary gland chromosomes of Sciara coprophila.

Synthesis and transport of proteins to the cell nucleus during puff induction was studied in S. coprophila. Changes in grain distribution along chromosomes (L-methionine [35S] incorporation into protein) were correlated with puffs induced by ecdysterone in vitro; A pattern of specific labelling at the sites of incipient puffs was noted within 2 h after the addition of the hormone, i.e. grains on the chromosomes were in clusters, characteristic for this time point and not seen in the controls (where only non-specific labeling was noted 0-4 h). Characteristic chromosomal puffs appeared between 3-4 h after the addition of ecdysterone. It was concluded that during ecdysterone-induced puff formation in salivary gland chromosomes, proteins which had been previously synthesized were selectively transported from the cytoplasm to specific sites on the chromosomes.     

Silicon in rat liver organelles: Electron probe microanalysis

Summary Electron probe microanalysis of unfixed freeze-substituted rat liver tissue embedded in Spurr's low viscosity epoxy resin demonstrated the occurrence of Si as well as P, S, and Cl in the nucleus, nucleolus, mitochondria, and rough endoplasmic reticulum. Chemical analysis confirmed that the Si in the organelles did not originate from instrumental contaminants. This suggests that Si may be involved in the biochemistry of these subcellular organelles.Supported by Grant GM-08229-12-13 from the National Institutes of Health, USPHS.We are grateful to the Kevex Corporation and Mr. Glenn W. Meyer, Sales Engineer, for the use of the Kevex X-ray spectrometer; we wish to thank as well the Perkin-Elmer Corporation and their Western Branch Manager, Mr. Michael E. Mullen and Senior Microscopist, Mr. Minoru Shinorhara, for use of and assistance with the Hitachi HU 12 A transmission electron microscope. We also wish to acknowledge Mary Louise Chiappino for her technical assistance in preparing the thin sections, the final micrographs and the X-ray photographs, and Darlene Lum for technical assistance in the laboratory.     

Strain distribution and linkage relationship of a mouse embryonic hemoglobin variant

Search for structural variants of three globin chains (x, y, z), synthesized only during mouse embryonic hematopoiesis, was carried out by electrophoretic analysis of blood from 12-day embryos, all with C57BL/6 mothers, and fathers from 115 inbred stocks selected for their diverse genetic origins. Structure of the -chains of adult hemoglobins differed among the tested strains, with 57 carrying the Hbb ^sallele, 56 the Hbb ^dallele, and two the Hbb ^pallele. The search revealed no x- or z-chain variants but confirmed and extended knowledge of a previously described y-chain variant. Blood of all embryos sired by males from the 57 Hbb ^sstrains contained only y¹-chains, while blood of all embryos sired by Hbb ^dor Hbb ^pmales contained y2-chains as well as the y¹-chains inherited from their C57 BL/6 mother. The locus controlling structure of the y-chain of mouse embryonic hemoglobins is thus extremely closely linked to the locus controlling structure of adult hemoglobin -chain, with maximum possible recombination frequency less than 0.019.This work was supported in part by Grants CA-01074 from the National Cancer Institute, USPHS, and GM 18684 from the National Institute of General Medical Sciences, in part by Grant ACS-VC58 from The American Cancer Society, in part by grants to the Jackson Laboratory from the Bushrod H. Campbell and Adah F. Hall Charity Fund and the Robert Sterling Clark Foundation, and in part by the Jackson Laboratory Endowment Fund. The Jackson Laboratory is fully accredited by the American Association for Accreditation of Laboratory Animal Care.     

Local Recurrence of Soft Tissue Sarcoma Revisited: Is there a Role for “Selective” Radiation?

BackgroundRadiation therapy (RT) is often utilized in cases of high-grade soft tissue sarcoma (STS), but there remain situations where treatment is with surgical excision alone. Our goals were to determine (1) the local recurrence (LR) rate with and without perioperative RT and (2) associations between local recurrence, patient, tumor, and treatment variables.MethodsWe performed a retrospective review of 165 consecutive STS patients. A Cox proportional hazards model was used to investigate variables associated with local recurrence.ResultsLR occurred in 15/78 (19%) without RT, 4/29 (14%) with postoperative RT, and 0/58 with preoperative RT (p=0.002). We found increased rates of local recurrence at 24 months for myxofibrosarcoma (p=0.001) and no-RT (p=0.003). Myxofibrosarcoma accounted for 33 (20%) of the study patients and 12 (63%) of the local recurrences.ConclusionThe LR rate in patients treated with surgery alone was disproportionately attributable to myxofibrosarcoma (11/23 cases, 48%). Other subtypes demonstrated a lower rate of LR in the absence of RT (4/55 cases, 7%), and no LR occurred when final margins were >2 mm. In certain circumstances treatment with a negative margin surgical resection followed by close observation is justifiable. RT is effective and should continue to be considered routinely in myxofibrosarcoma or when surgical margins are inadequate. Level of Evidence: III