DIFFUSE MESOTHELIOMA AND EXPOSURE TO ASBESTOS DUST IN THE MERSEYSIDE AREA

Synergistic anti-tumor effect of bullfrog sialic acid-binding lectin and pemetrexed in malignant mesothelioma

Malignant mesothelioma is an aggressive cancer with limited therapeutic options. Sialic acid-binding lectin isolated from Rana catesbeiana oocytes (cSBL) is a multifunctional protein with anti-cancer activity. The effects of pemetrexed, cisplatin, and cSBL were evaluated in mesothelioma and normal mesothelial cell lines. We evaluated cytotoxicity, apoptosis, caspase-3 cleavage and activation, cell proliferation, cell cycle arrest, and levels of cell cycle proteins in H28 cells treated with pemetrexed, cisplatin, and cSBL alone or in combination. Treatment with cSBL alone was cytotoxic to mesothelioma cells. The anti-cancer effect of cSBL was observed in a broader range of cell lines and exhibited greater cancer cell selectivity than pemetrexed or cisplatin. Combination treatment with pemetrexed + cSBL resulted in greater dose-dependent cytotoxicity than pemetrexed + cisplatin, the standard of care in mesothelioma. The synergistic effect of pemetrexed + cSBL was mediated by the cytostatic effect of pemetrexed and the cytotoxic effect of cSBL. It thus appears that cSBL has therapeutic potential for the treatment of mesothelioma.

History of asbestos related disease

The first medical article on the hazards of asbestos dust appeared in the British Medical Journal in 1924. Following inquiries by Edward Merewether and Charles Price, the British government introduced regulations to control dangerous dust emissions in UK asbestos factories. Until the 1960s these appeared to have addressed the problem effectively. Only then, with the discoveries that mesothelioma was an asbestos related disease and that workers other than those employed in the dustiest parts of asbestos factories were at risk, were the nature and scale of the hazard reassessed. In Britain, America, and elsewhere new and increasingly strict regulations were enacted.

A one-generation cluster of malignant mesothelioma within a family reveals exposure to asbestos-contaminated jute bags in Naples, Italy

Substantial evidence supports the role of asbestos in malignant mesothelioma. Clustering for this malignancy among relatives not only suggests genetic susceptibility as a relevant component but also provides a clue to investigate non-occupational sources of exposure. We identified five cases of malignant mesothelioma within one family with exposure to asbestos experienced during childhood, as 'next door' residents of a workshop recycling asbestos-contaminated jute sacks in Naples, Italy. This cluster discloses the health risk in the reuse of bags that previously had contained asbestos. Furthermore, it emphasizes the role of asbestos in the genetic-environmental interaction issue of malignant mesothelioma.

Radiological abnormalities among sheet-metal workers in the construction industry in the United States and Canada: relationship to asbestos exposure

We investigated the possible adverse health effects to sheet-metal workers who had past exposure to asbestos. A cross-sectional medical examination of 1,330 workers was conducted during 1986 and 1987 in seven cities in the United States and Canada. A total of 1,016 workers had been employed for at least 35 y in the industry, and the mean duration from onset of asbestos exposure was 39.5 y (SD = 7.41 y). Chest x-ray abnormalities were found in more than half of the group. Pleural fibrosis, the most frequently found abnormality, was present in 47.0% of the cases and was the only abnormality found in 27.8% of cases; parenchymal interstitial fibrosis, found in 33.1% of cases, was the only abnormality found in 16.2% of cases. Radiologic abnormalities increased as duration of exposure increased. A positive smoking history was associated with a higher prevalence of radiologically detectable parenchymal abnormalities, a finding confirmed by us and others. Dyspnea on exertion was graded by a Medical Research Council questionnaire, the examinee's self-assessment, and a more detailed 12-point scale questionnaire. Few persons had marked shortness of breath, and approximately one-third had slight dyspnea. Individuals who had radiologic abnormalities experienced more shortness of breath than did those who had no radiologic abnormalities. Cigarette smoking also resulted in a higher prevalence of dyspnea. The results indicate that during the past, construction sheet-metal workers have been significantly exposed to asbestos on the job. Every effort should be made to minimize the anticipated serious health consequences, and further asbestos exposure for those who continue in this trade should be avoided.

Changing attitudes and opinions regarding asbestos and cancer 1934-1965

Literature published in the years 1934-1965 was reviewed to determine attitudes and opinions of scientists as to whether asbestos is a cause of cancer. In Germany, the issue was decided in 1943 when the government decreed that lung cancer, when associated with asbestosis (of any degree), was an occupational disease. In the United States, however, there was no consensus on the issue until 1964. Opinions of scientists over a 22 year period are shown and the contributions of various cultural, social, economic and political factors to these opinions are discussed. A lack of experimental and epidemiological evidence played a major role in delaying a consensus. Other important factors included a rejection of science conducted outside of the U.S. during this period, particularly a rejection of German scientific thought during and after WWII, and a rejection of clinical evidence in favor of epidemiological investigations. Individual writers rarely changed their minds on the subject of asbestos as a cause of cancer.

Dysphagia complicating malignant mesothelioma

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Relationship between occupations and asbestos-fibre content of the lungs in patients with pleural mesothelioma, lung cancer, and other diseases

Whitwell, F., Scott, Jean, and Grimshaw, Myra (1977).Thorax, 32, 377-386. Relationship between occupations and asbestos-fibre content of the lungs in patients with pleural mesothelioma, lung cancer, and other diseases. The light-visible asbestos-fibre content of 300 lung specimens has been measured using a potash-digestion and phase-contrast microscopy technique, and the results have been correlated with the occupations of the patients.

Among 100 pleural mesothelioma specimens were 88 where the patients had been exposed to asbestos, and in 73 of these (83%) the lung tissue contained over 100 000 asbestos fibres per gram of dried lung, and only one specimen showed less than 20 000 fibres per gram. When asbestosis was present, the lungs nearly always showed over 3 million fibres per gram.

In 100 control lungs (those without industrial disease or lung cancer) there were less than 20 000 fibres per gram of dried lung in 71% of specimens. Lungs from 100 patients with lung cancer but no industrial disease contained less than 20 000 fibres per gram of dried lung in 80% of cases. Patients with parietal pleural plaques nearly all had over 20 000 fibres per gram in their lungs.

The number of asbestos fibres found in the lungs was closely related to the occupations of the patients but not to their home environment. Patients who had lived near likely sources of atmospheric asbestos pollution did not have higher asbestos fibre counts than the rest of the patients.

It is concluded that there is a definite dose relationship between asbestos exposure and mesothelioma formation but that' `sub-asbestosis' levels of asbestos exposure do not contribute to the formation of lung cancer in those not subjected to industrial asbestos exposure.

Malignant mesothelioma invading the spinal canal

A case of diffuse malignant pleural mesothelioma presenting as acute paraplegia is described. Autopsy revealed the presence of metastatic tumour within the spinal cord. An alveolar cell carcinoma coexisting with the mesothelioma and giving a distinct histological pattern was also present. There was no histological evidence of asbestos exposure.

Diffuse malignant pleural mesothelioma and asbestos exposure

Pleural mesothelioma has been diagnosed in 52 patients in three hospitals on Merseyside between 1955 and 1970, 60% being diagnosed from operation specimens and the rest from postmortem tissues. Necropsies eventually held on nearly half the operation cases confirmed the diagnosis, giving a necropsy rate of 70% for the series. The morbid anatomy conformed to earlier descriptions except that widespread metastases were much commoner than has usually been described. Histological findings agreed with previous accounts of the tumour, except that, in our hands, special acid mucopolysaccharide staining was less reliable than Southgate's mucicarmine, which was of value in differential diagnosis. Association with asbestos was confirmed from industrial histories in 80% of cases, the commonest industries involved being shipbuilding and repairing in men and sackware repairing in women. Lungs of industrial mesothelioma cases showed basal asbestosis in 17% and excessive asbestos bodies in almost all the rest. Quantitative comparison of asbestos bodies in lung smears from mesothelioma cases compared with lung smears from other Merseyside adults showed much higher counts in the mesothelioma cases. The interval from first exposure to asbestos until appearance of mesothelioma ranged between 13 and 63 years, with a mean of 42 years. We think the incidence of mesothelioma will continue to rise with the increased use of asbestos until about 40 years after adequate protective measures have been taken.

Pathological aspects of asbestosis

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