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That stimulates cell proliferation and often also promotes cell differentiation of specific target cells. Excluded from this class of agents are substances that are simply nutrients, such as glucose, essential amino acids, vitamins, and key minerals. The impetus for studies of growth factors largely derives from earlier observations that most mammalian cells growing in culture require the presence of animal serum to grow and proliferate. Numerous attempts have been made to isolate growth...

Validity of Tests for Carcinogenicity

There is quite a bit of debate among scientists and regulatory agencies about how to assess the carcinogenic hazards of chemicals, both man-made and natural, in our environment. Much of this debate has spilled over into the media, generating a sort of carcinogen-of-the-month club'' and much confusion among the public. Indeed, as one observer put it, ''Cancer news is a health hazard.''93 For many years, the prevailing view among cancer epidemiologists has been that 60 to 90 of human cancers are...

Description of Cancer

Cancer is a group of diseases of higher multicellular organisms. It is characterized by alterations in the expression of multiple genes, leading to dysregulation of the normal cellular program for cell division and cell differentiation. This results in an imbalance of cell replication and cell death that favors growth of a tumor cell population. The characteristics that delineate a malignant cancer from a benign tumor are the abilities to invade locally, to spread to regional lymph nodes, and...

Cancer Is a Global Problem

Cancer is clearly a worldwide problem. The incidence and mortality rates for various cancers are similar, though not identical, among developed countries. In the developing world, as countries become more westernized and their populations achieve longer life expectancy, cancer rates are increasing. Although there are differ ences among developing and developed countries in the incidence rates of certain cancers, lung cancer is the most common cancer among men in both regions of the world and...

Basic Facts About Cancer

Cancer is a complex family of diseases, and carcinogenesis, the events that turn a normal cell in the body into a cancer cell, is a complex multistep process. From a clinical point of view, cancer is a large group of diseases, perhaps up to a hundred or more, that vary in their age of onset, rate of growth, state of cellular differentiation, diagnostic detectability, invasiveness, metastatic potential, response to treatment, and prognosis. From a molecular and cell biological point of view,...

Biology Of Tumor Metastasis

The ''Classic'' Theory of Tumor Metastasis In humans, the earliest detectable malignant lesions are often referred to as in situ cancers Fig. 4-33 . These are small tumors usually only a few millimeters in diameter that are localized in tissues. They are usually detected only if they can be endoscopically or directly visualized, for instance, as in the case of carcinoma in situ of the uterine cervix, urinary bladder, or skin, or by examination of biopsy material, as for ductal carcinoma in situ...