Cancer genes and molecular oncology in the clinic

Gastric and colorectal cancer mortality in an urban and industrialized area of Brazil

PURPOSE

To study the gastric and colorectal cancer mortalities and their relation to the urban-industrialization in Baixada Santista, located in the southeastern region of Brazil.

METHODS

Selected from the registries of the State System of Data Analysis Foundation (SEADE) were 1105 deaths due to gastric cancer (ICD 153 - 154) and 690 due to colorectal cancer (ICD 151) that occurred from 1980 to 1993 in males, above 10 years of age, residing in Baixada Santista. For each of these types of cancer, the standardized mortality rates, age-adjusted by world population in the 1960s, for 4 industrialized and 4 non-industrialized urban communities in that region were calculated. The ratios among those rates were calculated in order to compare the mortality in the periods 1980 - 93, 1980 - 1986, and 1987 - 1993.

RESULTS

Standardized mortality rates for colorectal cancer were significantly higher in industrialized area, with ratios of 1.6 [95% CI 1.22 - 2.29], 1.6 [95% CI 1.2 - 2.0], and 1.6 [95% CI 1.3 - 2.0] in the periods 1980 - 86, 1987 - 1993 and 1980 - 93, respectively. Gastric cancer did not show any statistical difference between the industrialized and non-industrialized areas, but there was a significant decrease in BS from the period 1980 - 1986 to 1987 - 1993.

CONCLUSIONS

The significant elevation of colorectal cancer mortality in the industrialized area could be related to exposure to numerous carcinogens such as aromatic hydrocarbon, organic-chloride, metals, and industrial-port dust present in the region. Alternatively, the non-significant difference in gastric cancer between industrialized and non-industrialized areas and significant decrease in the last few years could be predominately reflecting the advances in the quality of life in urban areas. These results require further case-control studies that could help with the analysis of the associations among cancer and environmental factors (occupational, urban-industrial, habit, and life condition) and genetic susceptibility.

Induced genome instability as a potential screening test for cancer susceptibility?

The variety of mutations associated with carcinogenesis, along with variations in penetrance and environmental factors, complicate the genetic screening for cancer predisposition. It is proposed here that the detection of inherent genome instability as determined by increased mutagen susceptibility may enhance the identification of populations at risk for cancer. In support for this hypothesis, our analysis reveals a strong association between mutagen-induced chromosomal instability in peripheral blood lymphocytes and the propensity for cancers of oral cavity, pharynx, larynx, and lung. DNA instability in response to a variety of mutagens identifies patients with gastrointestinal, brain, endocrine, breast, skin, and hematologic tumors as well as individuals with cancer family syndromes. Induced genome instability therefore appears to be strongly linked to cancer predisposition, and prospective studies may yield a screening test utilizing a panel of mutagens to better identify populations at risk.

Molecular biology of pancreatic cancer; oncogenes, tumour suppressor genes, growth factors, and their receptors from a clinical perspective

Pancreatic cancer represents the fourth leading cause of cancer death in men and the fifth in women. Prognosis remains dismal, mainly because the diagnosis is made late in the clinical course of the disease. The need to improve the diagnosis, detection, and treatment of pancreatic cancer is great. It is in this type of cancer, in which the mortality is so great and the clinical detection so difficult that the recent advances of molecular biology may have a significant impact. Genetic alterations can be detected at different levels. These alterations include oncogene mutations (most commonly, K-ras mutations, which occur in 75% to more than 95% of pancreatic cancer tissues), tumour suppressor genes alterations (mainly, p53, p16, DCC, etc.), overexpression of growth factors (such as EGF, TGF alpha, TGF beta 1-3, aFGF, bTGF, etc.) and their receptors (i.e., EGF receptor, TGF beta receptor I-III, etc.). Insights into the molecular genetics of pancreatic carcinogenesis are beginning to form a genetic model for pancreatic cancer and its precursors. These improvements in our understanding of the molecular biology of pancreatic cancer are not simply of research interest, but may have clinical implications, such as risk assessment, early diagnosis, treatment, and prognosis evaluation.