In vitro radiation resistance among cell lines established from patients with squamous cell carcinoma of the head and neck

Article Abstract:

Radiotherapy is an integral part of the therapy for cancer of the head and neck. Unfortunately, not all cancers are equally susceptible to the effects of radiation, and many such cancers recur after radiation treatment. Researchers have speculated that some cancers are more resistant to irradiation because of purely physical factors such as their size and location. Other factors, such as the ulceration of a tumor and its stage of development, also seem to be important. A key factor seems to be the adequacy of the blood supply of the tumor; tumors which are poorly supplied with oxygen may have a greater chance of surviving radiation than those which are well oxygenated. However, two tumors which appear to be the same are often entirely different in their susceptibility to radiation. Some researchers have suggested that this is due to differences in the ability of the cancer cells themselves to repair the damage which is inflicted by the radiation. One way to approach this problem is to obtain cells from the cancers of human patients and grow them in tissue culture dishes, where there are no differences in oxygen supply. In this way, the response of cells to radiation may be studied without the influence of such variables. For this reason, cells were cultured from tumor specimens removed from 20 patients with cancer of the head and neck. Some of the cell lines which were established were found to be resistant to radiation, and others were radiosensitive. Radioresistant cells were obtained both from patients who had previously received radiation treatment and patients who had not. Similarly, radiosensitive cells were obtained even from patients whose cancer had recurred after radiotherapy. However, when only the radioresistant cells were compared, the amount of radiation required to kill a specified proportion of the cells from the previously irradiated patients was significantly higher than the radiation dose required to kill a similar fraction of cells from the other patients. These results indicate that resistance to radiation appears to be, at least in part, an intrinsic characteristic of the cancer cells themselves, and is not due entirely to the physical characteristics of the patient's original tumor. The physiological basis for this radiation resistance has not yet been identified, however. (Consumer Summary produced by Reliance Medical Information, Inc.)

Research, Reports, Cancer cells, Cell research, Cytological research, Head and neck cancer

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DNA image cytometry: a prognostic tool in squamous cell carcinoma of the esophagus?

Article Abstract:

Historically, in the examination of a cancer, the most important features are the stage and grade. Stage refers to whether the cancer is at an earlier or more advanced point in its development. Grade refers to the appearance of the cancer tissue under the microscope (histopathology); low-grade tumors more closely resemble normal tissues, while high-grade tumors do not and are likely to be highly malignant (become cancerous). More recently, it has become possible to measure the DNA content of individual cells. The profile of the DNA content of cells in a tumor specimen has proved to be a useful prognostic indicator for many types of cancer. Many studies of the DNA content of tumor cells have used the flow cytometer. This instrument requires that the tumor be broken up into a suspension of individual cells which are then analyzed one-by-one as they trickle past an intricate optical device. This method can not distinguish between actual tumor cells and cells from blood vessels within the tumor, and other normal cells that might be complicating the specimen. These problems may be circumvented using image analysis. This method, which is essentially an automated microscope, offers the added advantage of differentiating contaminating blood cells from tumor cells and eliminates artifacts that may result from the tissue treatment, such as several cells sticking together and masquerading as a large single cell. This image analysis technique was used to measure the DNA content of esophageal cancer specimens from 45 patients. Patients with tumors having a diploid DNA content, that is, a normal complement of chromosomes, survived an average of 32 months. In contrast, the patients whose tumors' DNA content was abnormal, but less than 50 percent above normal, survived an average of 22 months. Patients whose tumors had DNA in excess of 50 percent above normal survived an average of only 6.5 months. No correlation was found between the DNA content and the more traditional prognostic indicators of stage and grade. This observation suggests that DNA content may be an effective way of identifying patients with a poor prognosis. In a group of patients with the same stage of esophageal cancer, the patients with the most normal DNA content in their tumors enjoy the best prognosis. (Consumer Summary produced by Reliance Medical Information, Inc.)

Methods, Cases, Measurement, Physiological aspects, DNA, Esophageal cancer, Photometry, Predictive value of tests, Predictive value of tests (Medical)

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Intraoral squamous cell carcinoma: epidemiological patterns in Connecticut from 1935 to 1985

Article Abstract:

The Connecticut State Tumor Registry recorded 6,181 cases of squamous cell carcinoma of the oral cavity between 1935 and 1985. The age-adjusted incidence rate rose for both men and women during this period. While the rate for men is higher, the rate for women increased more rapidly, and thus the ratio of men to women with this cancer has decreased. In the period from 1980 to 1985, intraoral squamous cell carcinoma had an incidence of 8.5 cases per 100,000 men and 3.3 cases per 100,000 women. Cancer of the oral cavity accounts for between 2 and 4 percent of all cancers in the United States, and about 2 percent of all cancer deaths among men and about 1 percent of all cancer deaths among women. It is well recognized that 90 percent of cancers within the oral cavity are squamous cell carcinomas. In the present study, the tongue was found to be the most common location of the cancer, with the floor of the mouth next most common. These results, which confirm previous reports, are consistent with the role of tobacco consumption as a major risk factor. The floor of the mouth is thought to be susceptible because it represents a collecting pool for saliva laden with cancer-causing substances. The over six-fold increase in intraoral squamous cell carcinoma among women is also consistent with tobacco use as a major risk factor, as the consequences of increased tobacco use among women, which began in the 1920s and 1930s, are taking effect. The peak incidence of intraoral squamous cell carcinoma occurs in the seventh decade of life. While tobacco and alcohol are statistically associated with increased incidence of oral cancer, further studies will be necessary to confirm a causative role. Furthermore, additional study will be required to determine if other, as yet unidentified, causes of intraoral cancer may be contributing to the increases observed in the present study. (Consumer Summary produced by Reliance Medical Information, Inc.)

Causes of, Demographic aspects, Mouth cancer, Throat cancer, Pharyngeal cancer

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