Types of Cancers

It may also be noted, as per an Encyclopedia Britannica article, subsequently to be cited, that retroviruses are often defective and require the assistance of other, nondefective helper retroviruses. (In retroviruses, which are commonly associated with cancer, the RNA provides the cellular instructions rather than the DNA.) Usually, these helper viruses are involved in transforming fibroblastic cells, as in connective tissue, and the result is malignant sarcomas. Otherwise, without assistance, the defective retroviruses will act to transform blood cell precursors, and the end result is leukemia. 

It may be added that melanomas, which may or may not become malignant, constitute still another category, with the differences in chemotherapeutical 

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Another monoterpene used as a starting material for taxol analogues is camphor (43), which is readily available naturally or can be produced synthetically (201,202). Total synthesis of taxol analogues may be the answer toward finding new compounds for the treatment of many types of cancer. 

When the data as a whole are reviewed for studies on humans exposed to ethylene oxide, no conclusion can be made that there is an increase in mortahty associated with those exposed to ethylene oxide. Two Swedish studies (247,248) indicated an increase in leukemia for workers exposed to multiple chemicals including ethylene oxide however, in a recent larger Swedish study (249) of workers exposed to only ethylene oxide, there was no association of any type of cancer increase for these workers. In a recent study sponsored by NIOSH, there was no significant increase in mortahty observed for cancer when all types are combined or for certain individual types of cancer, even for those people who worked the longest and were observed the longest. However, a statistically significant increase in mortahty from certain types of lymphoma was observed for male workers. This is contrary to the results observed for female workers. In addition, four other cohort studies of ethylene oxide-exposed workers have been pubhshed (250—253), but no unequivocal increase in the risk of cancer was observed. 

In recent year s, clinical studies on the role of uiinai y luodified nucleosides as the biochemical mai kers of various types of cancer have been actively undertaken. Most of the urinai y modified nucleosides ai e piimai ily originated by methylation of either the base part, the sugar hydroxyl par t, or in some cases, both par ts of the course of biodegradation of tRNA molecules. Hence, their isolation and identification plays a major role in biochemical analysis. 

Chemical-mediated immune suppression has been identified from the experimental study of several wildlife species. Harbour seals fed either chemically contaminated fish from the Wadden Sea or imcontaminated fish were found to have differing immune responses, with the exposed group showing lowered immune response to microbial infections and certain types of cancer. "" Mink fed fish taken from below a discharge point for bleached Kraft pulp mill effluent have also shown impaired immune function, " showing that the non-accnmillative chemicals in this effluent can actively disrupt endocrine associated functions. 

An alkene, sometimes caJled an olefin, is a hydrocarbon that contains a carbon-carbon double bond. Alkenes occur abundantly in nature. Ethylene, for instance, is a plant hormone that induces ripening in fruit, and o-pinene is the major component of turpentine. Life itself would be impossible without such alkenes as /3-carotene, a compound that contains 11 double bonds. An orange pigment responsible for the color of carrots, /3-carotene is a valuable dietary source of vitamin A and is thought to offer some protection against certain types of cancer. 

Diethylstilbestrol (DES) has estrogenic activity even though it is structurally unrelated to steroids. Once used as an additive in animal feed, DES has been implicated as a causative agent in several types of cancer. Show how DES can be drawn so that it is sterically similar to estradiol. 

There is considerable evidence to suggest that selenium compounds are anticarcinogens. For one thing, tests with laboratory animals show that the incidence and size of malignant tumors are reduced when a solution containing Na2Se03 is injected at the part per million level. Beyond that evidence, statistical studies show an inverse correlation between selenium levels in the soil and the incidence of certain types of cancer. 

The list of MoAb or fusion proteins used in treatment of every type of cancer is continually growing as research identifies more cancer-associated antigens. MoAb targeting a tumor-specific antigen is used... 

A large and rapidly growing number of clinical trials (phase I and phase II) evaluating the potential of DNA vaccines to treat and prevent a variety of human diseases are currently being performed ( http // clinicaltrials.gov) however, there is yet no licensed DNA vaccine product available for use in humans. The clinical trials include the treatment of various types of cancers (e.g., melanoma, breast, renal, lymphoma, prostate, and pancreas) and also the prevention and therapy of infectious diseases (e.g., HIV/ABDS, malaria, Hepatitis B vims, Influenza vims, and Dengue vims). So far, no principally adverse effects have been reported from these trials. The main challenge for the development of DNA vaccines for use in humans is to improve the rather weak potency. DNA vaccines are already commercially available for veterinary medicine for prevention of West Nile Vims infections in horses and Infectious Hematopoetic Necrosis Vims in Salmon. 

The epidermal growth factor receptor 2 (HER-2) is a protein found on the surface of cells. Heterodimerization of HER-2 activates the enzyme tyrosine kinase, triggering reactions that cause the cells to grow and multiply. HER-2 is found at abnormally high levels on the surface of many types of cancer cells, which may divide excessively. Antibodies targeting HER-2 (e.g., trastuzumab) are used as antineoplastic agents. 

Despite recent developments, effectiveness of chemotherapy is still rather limited for most types of cancer, including tumors of the colon, lung, kidney, pancreas, and liver. Why some cancers respond better than others may be explained by factors relating to the anatomy and physiology of the cancer-ridden organ or... 

PTEN Cowden disease, Bannayan-Riley-Ruvalcaba syndrome, Proteus syndrome, Lhermitte-Duclos disease overgrowths of various organs, hamartomas of the skin, mucosa, cerebellar cortex high risk of developing several types of cancer. Spontaneous pten mutations found frequently in human cancers... 

More TKIs directed against other tyrosine kinases, like c-Met, IGF1R, Flt-3, FGFRs, Tie-2, Axl or Ron are at earlier stages of development with the most advanced candidates having entered phase II studies in different types of cancers. 

OTRs are mainly expressed in myoepithelial cells of the galactiferus channels and the myometrium. The OTRs in vascular endothelial cells, renal epithelial cells (macula densa, proximal tubule) and cardiomyocytes induce the production of NO (vasodilation), natriuresis and release of ANP, respectively. The endometrium, ovary, amnion, testis, epididymis, prostate and thymus also express the OTR supporting a paracrine role of this peptide. Osteoblasts, osteoclasts, pancreatic islets cells, adipocytes, and several types of cancer cells also express OTRs. More over, expression of the OTR... 

An interesting application of the photodynamic properties of porphyrins is their possible use in the treatment of certain types of cancer, a procedure called cancer phototherapy. Tumors often take up more porphyrins than do normal tissues. Thus, hematopor-phyrin or other related compounds are administered to a patient with an appropriate mmor. The mmor is then exposed to an argon laser, which excites the porphyrins, producing cytotoxic effects. 

Certain drugs bind to microtubules and thus interfere with their assembly or disassembly. These include colchicine (used for treatment of acute gouty arthritis), vinblastine (a vinca alkaloid used for treating certain types of cancer), paclitaxel (Taxol) (effective against ovarian cancer), and griseoflilvin (an antifungal agent). 

A developing application of DNA technology uses a DNA chip that contains many small segments of bases of known sequence. Such DNA chips are being used to attack cancers. Cancers occur when defective genes cause cells to divide uncontrollably, but usually the process of protein synthesis also is modified. Different types of cancer result in different modifications to protein synthesis, depending on how the DNA... 

Some laboratory studies with rats and mice have linked trichloroethylene exposure to various types of cancers. Several of these studies, however, should be viewed cautiously, since the tumorigenic activity might be influenced by the presence of direct-acting compounds, namely the epoxides (e.g., epichlorohydrin) added as stabilizers in trichloroethylene. Epoxides are known to be very reactive, and some, such as epichlorohydrin, are potent carcinogens themselves. 

The discovery that, in industrialised societies, diets deficient in fruits and vegetables can effectively double the risk of developing many different types of cancer has focused renewed attention on the beneficial properties of these foods (Block e/a/., 1992 Patterson ef a/., 1990 Southon and Faulks, 2002). As we have seen, plant foods are rich in micronutrients, but they also contain an immense variety of biologically active secondary metabolites providing colour, flavour and natural toxicity to pests and sometimes humans (Johnson et ah, 1994). The chemistry and classification of such substances is still a matter for much research and debate, but this has not prevented attempts to isolate and exploit substances that have variously been termed protective factors , phytoprotectants , phytochemicals and nutraceuticals . Phytochemical compounds include ... 

Between 1900 and 1950, gastric cancer was one of the major types of cancer in the United States. Its incidence and mortality have decreased sharply since 1950 (41), and the concepts presented in this paper account for this decline. In other parts of the world, including Japan, the mountainous interior regions of Central and Western Latin America, and in Northern and Eastern Europe, as well as in Iceland, gastric cancer remains one of the major cancers. There is a North-South gradient, or South-North in the Southern hemisphere, with greater incidence in more frigid zones. 

Many epidemiological studies have analyzed the correlations between different carotenoids and the various forms of cancer and a lot of conclusions converge toward protective effects of carotenoids. Many studies were carried out with (i-carotene. The SUVIMAX study, a primary intervention trial of the health effects of antioxidant vitamins and minerals, revealed that a supplementation of p-carotene (6 mg/day) was inversely correlated with total cancer risk. Intervention studies investigating the association between carotenoids and different types of cancers and cardiovascular diseases are reported in Table 3.1.2 and Table 3.1.3. 

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