Characteristics of Tumor Cells

Tumor cells have special features compared to normal cells. The phenotype of a tumor cell is characterized by the following characteristics  

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Growth factors are paracrine or endocrine agents, peptides or proteins, released by one cell to regnlate proliferation in adjacent cells (chapter 12) (Table 21.4). Normal cell proliferation requires the presence of growth factors but proliferation of tumonr cells reqnires either no growth factors or much lower concentrations. There are several different characteristics of tumor cells that enable them to respond to very low concentrations of growth factors ... 

Over-Expression of A3AR Is a Characteristic of Tumor Cells... 

A great number of tissue-specific promoters has been isolated and characterized, and some of these have been used in experimental cancer gene therapy (see Table 1). Obviously, tissue-specific promoters are also active in the normal tissue from which the tumor originated. Unless the loss of these normal cells is acceptable (as in the case of melanocytes), additional specificity mechanisms need to be considered to make the resulting vector useful for a systemic delivery. This can be achieved, for example, by introducing an additional level of specificity, such as a specificity for proliferating cells or a selectivity for other conditions that are characteristic of tumor cells (see later). 

Since the uncontrolled proliferation is a peculiar characteristic of cancer cells, the proteins involved in DNA replication are attractive targets in modem chemotherapy. Several preclinical works showed in colorectal tumors, higher... 

Tumor heterogeneity refers to the existence of distinct subpopulations of tumor cells with specific characteristics within a single neoplasm. Breast cancer is a classic example of a heterogeneous disease. First, the term breast cancer does not itself refer to a single disease. Breast cancers include many different diseases including (but not limited to) adenomas, papillomas, invasive ductal carcinoma, ductal carcinoma in situ (DCIS), and lobular carcinoma in situ (LCIS) (6). 

The antibody-dependent lysis of tumor cells by PMNs exhibited some of the characteristics of damage mediated by products of the burst in the presence of tumor cells there was increased consumption of O2, increased formation of O and activation of the hexose monosphosphate shunt However, although a reduction in the concentration of O2 in the medium inhibited lysis neither catalase nor superoxide dismutase inhibited. The lack of effect on these enzymes was attributed to their inability to interpose themselves between the plasma membranes of the PMN and its target. Similar conclusions were reached by Clark, and Klebanoff whose data incriminated the products of the burst by the reduced killing of tumor cells by PMNs from patients with chronic granulomatous disease. Myeloperoxidase, however, appeared not to he required since neither azide or cyanide inhibited and killing by PMNs from patients with inherited deficiency of myeloperoxidase was normal. 

An important characteristic of cancer cells is their uncontrolled proliferation. They don t respond to the normal signals from adjacent cells that indicate that cell division should stop. Cancer cells also differ dramatically from those present in warts and other benign tumors and in psoriasis. These conditions also result in excessive proliferation of cells and partial derangement of normal regulatory processes. 

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