The molecular biology of radiation-induced carcinogenesis: thymic lymphoma, myeloid leukaemia and osteosarcoma

Reprint of: cancer "causation" by infections--individual contributions and synergistic networks

The search for infectious agents playing a role in human carcinogenesis and their identification remain important issues. This could provide clues for a broader spectrum of cancers preventable by vaccination and accessible to specific therapeutic regimens. Yet, the various ways of interacting among different factors functioning synergistically and their different modes of affecting individual cells should bring to question the validity of the term "causation". It also should put a word of caution into all attempts to summarize criteria for "causality" of infectious agents in cancer development. At least in the opinion of these authors, we would be much better off avoiding these terms, replacing "causal factor" by "risk factor" and grading them according to their contribution to an individual's cancer risk.

Cancer "causation" by infections--individual contributions and synergistic networks

The search for infectious agents playing a role in human carcinogenesis and their identification remain important issues. This could provide clues for a broader spectrum of cancers preventable by vaccination and accessible to specific therapeutic regimens. Yet, the various ways of interacting among different factors functioning synergistically and their different modes of affecting individual cells should bring to question the validity of the term "causation". It also should put a word of caution into all attempts to summarize criteria for "causality" of infectious agents in cancer development. At least in the opinion of these authors, we would be much better off avoiding these terms, replacing "causal factor" by "risk factor" and grading them according to their contribution to an individual's cancer risk.

Strain differences in carcinogenic and hematopoietic responses of mice after injection of plutonium citrate

The carcinogenicity of injected (239)Pu citrate was compared in female mice of the C3H, C57BL/6 and BC3F(1) hybrid strains with different spectra of spontaneous or radiation-induced tumors. A significant reduction in survival due to early death caused particularly by the induction of osteosarcomas was noted in each strain after injection of 500 Bq or more. The dose response of osteosarcomas appeared to have a similar pattern in each strain except for the differences in the skeletal dose ranges for the maximum induction. While the incidence of lymphoid tumors decreased as that of osteosarcomas increased sharply to the maximum at higher doses, their histological phenotypes were predominantly non-thymic, pre-B-cell leukemic lymphomas compared to the controls in each strain. Myeloid leukemias were not highly induced in any of the control and (239)Pu-injected mice, and solid tumors involving the other organs were reduced in each strain after injection of 500 Bq or more. To follow up the hematological kinetics related to alpha-particle irradiation of bone marrow stem cells, sequential examinations were done in mice of each strain within 1 year after injection of 5000 Bq. The numbers of peripheral white blood cells and bone marrow cells were consistently reduced in each strain from 90 days on, while spleen cells increased from 180 days on. Granulocyte-macrophage and macrophage colony-forming cells were also consistently reduced in the bone marrow, with a compensatory increase in the spleen from 90 days on. These findings indicate that the carcinogenic and hematopoietic responses were specific to alpha-particle irradiation and were independent of mouse strain after injection with (239)Pu citrate.

Clinicopathologic features and treatment of postirradiation sarcoma of bone and soft tissue

BACKGROUND AND OBJECTIVES

An analysis of the clinicopathologic features and treatment of patients with postirradiation sarcoma of bone and soft tissue was performed to guide modern evaluation and management.

METHODS

A retrospective analysis of 135 sarcomas in 130 patients was performed.

RESULTS

The mean age of the 130 patients was 48 years, and there was a female predominance because of irradiation for carcinomas of the breast and uterus. Indication for irradiation was a soft tissue lesion (such as lymphoma or breast cancer) in 58.5% of patients and a bone lesion (such as giant cell tumor or fibrous dysplasia) in 41.5%. The latent period (interval between irradiation and discovery of the sarcoma) ranged from 4-55 years (mean, 17 years). Of the lesions, 74% were stage IIB (high-grade extra-compartmental) and 24% were stage III (metastases). Ninety-four patients received their treatment at our institution. Of the 61 patients with resectable disease, 49 had amputations and 12 had limb salvage procedures. The 5-year cumulative survival rate was 68.2% for patients with peripheral (extremities, including proximal femur and hip) resectable lesions and 27.3% for patients with central (pelvis, head/neck, and ribs) resectable lesions. The local recurrence rate correlated with the surgical margin achieved: intralesional, 73%, marginal, 64%, and wide, 23%.

CONCLUSIONS

The prognosis for patients with peripheral resectable postirradiation sarcomas is good if a wide surgical margin can be achieved. This group of patients should be treated aggressively because they have a new cancer.

Targeted disruption of ATM leads to growth retardation, chromosomal fragmentation during meiosis, immune defects, and thymic lymphoma

ATM, the gene mutated in the inherited human disease ataxia-telangiectasia, is a member of a family of kinases involved in DNA metabolism and cell-cycle checkpoint control. To help clarify the physiological roles of the ATM protein, we disrupted the ATM gene in mice through homologous recombination. Initial evaluation of the ATM knockout animals indicates that inactivation of the mouse ATM gene recreates much of the phenotype of ataxia-telangiectasia. The homozygous mutant (ATM-/-) mice are viable, growth-retarded, and infertile. The infertility of ATM-/- mice results from meiotic failure. Meiosis is arrested at the zygotene/pachytene stage of prophase I as a result of abnormal chromosomal synapsis and subsequent chromosome fragmentation. Immune defects also are evident in ATM-/- mice, including reduced numbers of B220+CD43- pre-B cells, thymocytes, and peripheral T cells, as well as functional impairment of T-cell-dependent immune responses. The cerebella of ATM-/- mice appear normal by histologic examination at 3 to 4 months and the mice have no gross behavioral abnormalities. The majority of mutant mice rapidly develop thymic lymphomas and die before 4 months of age. These findings indicate that the ATM gene product plays an essential role in a diverse group of cellular processes, including meiosis, the normal growth of somatic tissues, immune development, and tumor suppression.

Biological significance of human endogenous retroviral sequences

Endogenous retroviruses (ERVs) have been known for many years to exist in numerous natural and laboratory animal species. In humans it has been demonstrated that at least 1% of the genome consists of retrovirus-related sequences. Involvement of ERVs in the development of neoplastic and autoimmune diseases in the mouse model implicated a potentially pathogenic role of ERVs for humans, too. The research in this field led to a number of results strongly suggesting that human endogenous retroviral sequences (HERVs) are biologically active, on the RNA and even on the protein level. Particle formation, regulation or dysregulation of cellular gene expression, and synthesis of potentially pathogenic viral proteins indicate the broad spectrum of mechanisms by which HERVs may obtain biological significance.

Brief chemotherapy, involved field radiation therapy, and central nervous system prophylaxis for paranasal sinus lymphoma

Lymphoma of the paranasal sinus is a rare tumor characterized by bulky local disease, early systemic dissemination, and a propensity for central nervous system (CNS) spread. Treatment with radiation alone generally has been disappointing. Based on previous encouraging reports of initial brief chemotherapy followed by involved field radiation therapy (IFRT) for localized large cell lymphoma, four consecutive patients with paranasal sinus lymphoma were treated with 6 weeks of chemotherapy followed by IFRT and CNS prophylaxis. All patients had bulky localized disease and diffuse large cell lymphoma. Complete response was seen in all patients, and none have had a relapse (minimum follow-up, 25 months; range, 25 to 32 months). Chemotherapy and radiation therapy were well tolerated. One patient developed an osteogenic sarcoma in the radiation field 32 months after completion of therapy. Administration of early frequent chemotherapy followed by IFRT and CNS prophylaxis appears to be an effective treatment strategy for patients with localized large cell lymphoma of the paranasal sinuses.

Is there a link between fluoridated water and osteosarcoma?

To test the hypothesis that fluoride is a risk factor for osteosarcoma, a case control study compared the complete residential fluoride histories of osteosarcoma patients with matched hospital-based controls. Fluoridation was not found to be a risk factor for osteosarcoma in the study population. The trend in the data from this small sample study suggests the hypothesis that a protective effect may exist against the formation of osteosarcoma for individuals consuming fluoridated water.