New insights into the causes of cancer

JL, Cypriano M, Angel A, Toledo S. Diferenças clínicas, epidemiológicas e biológicas entre o câncer na criança e no adulto

O câncer representa hoje a primeira causa de morte por doença entre a população de faixa etária compreendida entre 1 e 21 anos nos Estados Unidos e em outros países economicamente desenvolvidos. No Brasil, esta doença figura como a terceira causa de morte por doença entre a população de faixa etária compreendida entre 1 e 14 anos, sendo já a primeira causa de óbito no município e no estado de São Paulo no grupo etário compreendido entre 5 e 14 anos, excluindo-se acidentes e causas externas. O objetivo deste artigo é informar a classe médica, principalmente a pediátrica, das particularidades do câncer infantil e de suas diferenças com as formas dos adultos, mais conhecidas e frequentes. Graças à moderna abordagem multidisciplinar, o câncer infantil pode atingir índices de cura de 60% a 70%, mas, para tal, é imprescindível o diagnóstico precoce. Portanto, é importante que toda a comunidade pediátrica mostre-se motivada e informada sobre os sinais e sintomas das neoplasias pediátricas, já que não dispomos de métodos de “screening” tão úteis e eficazes como para o controle do câncer do adulto.

Immunological implications of alterations in the c-Ki-ras and p53 genes in the stepwise progression of colorectal cancer: indications for the improvement of prognosis, biotherapy treatment and tumor biology understanding

Alterations in gene structure and functions involving the c-Ki-ras and p53 genes have been shown to play an important role in the various stages of human colorectal carcinogenesis. However, how these gene alterations cooperate with tumoral mechanisms at an immunological level is not known. To this aim an immunological study of a group of healthy subjects, patients with p53 gene deletions (53D), with c-Ki-ras mutations (KrM) and no gene alterations (53D-KrM-) have made. In a previous study we found that a disregulation between TH1/Th2 cell functions seems to be implicated in the establishment and progression of colorectal cancer disease and that soluble interleukin (IL)-2Receptor (sIL-2R) serum level is involved in this. On this basis we investigated the immunological implications of p53 and c.Ki-ras gene alterations, evaluating the relationhips in the immune network between sIL-2R levels in the serum and immunological parameters (IL-2, IL-4 serum levels; CD3, CD16 and CD19 expression on the surface of peripheral blood mononuclear cells--PBMC). Our results suggest that, in the stepwise progression of colorectal cancer, the c-Ki-ras gene alteration is involved in a switch of the host immune response to a suppressive type which, as we have previously reported, may be a determining or concurrent cause of malignant transformation. Alteration in the p53 gene does not appear to ulteriorly impair the patients' immunological response. Our data supports the role of c-Ki-ras gene mutations and p53 deletions as prognostic markers in the passage of normal tissue to adenoma and adenoma to carcinoma respectively. Moreover, the evaluation of the mechanisms involved in the alterations of c-Ki-ras gene seems to be more important than that of p53 suppressor gene for the improvement of prevention, biotherapy treatment and tumor biology understanding.

Chemokines induce migrational responses in human breast carcinoma cell lines

Chemokines have been shown to chemoattract and activate different leukocyte populations. Here we report the in vitro effect of macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, regulated on activation, normal T-cells, expressed and secreted (RANTES), monocyte chemotactic protein-1 (MCP-1), interleukin-8 (IL-8), interferon inducible protein-10 (IP-10), neutrophil-activating peptide-2 (NAP-2), growth-related protein (GRO)-alpha and GRO-gamma, on the migration of 3 human breast carcinoma cell lines, MCF-7, T47D and ZR-75-1, using a microchemotaxis chamber to assess migration across fibronectin-coated polycarbonate membranes. MCF-7 cells responded chemotactically to all chemokines tested in a pattern which was dose and time dependent, although responses to the different chemokines were variable. ZR-75-1 responded to MIP-1beta and GRO-alpha, giving maximum migration indices of 3.7 and 5.3, respectively, and exhibited a migratory response to MIP-1alpha, IL-8 and MCP-1 although to a lower degree. T47D was unresponsive to the chemokines tested, but both MCF-7 and T47D cells bound radiolabelled ligands with binding constants (Kd) ranging from 0.6 to 2.2 nM and 0.6 to 2.1 nM, respectively. The specificity of the chemotactic response of MCF-7 to MIP-1alpha and MIP-1beta was confirmed using chemokine-specific neutralising antibodies and heat denaturation, and was demonstrated to involve G protein and cyclic AMP signalling pathways. MIP-1beta and MIP-1alpha were shown to induce changes in the organisation of the actin cytoskeleton and the level of F-actin in MCF-7 cells, as determined using flow cytometric analysis and confocal microscopy. Our results show that breast carcinoma cells can respond to chemokines, and suggests a potential role for these molecules in the process of tumour cell migration, invasion and metastasis.

Carcinogenesis of cutaneous malignancies

BACKGROUND

Over the past several years significant progress has been made in identifying the cellular and biochemical mechanisms underlying carcinogenesis.

OBJECTIVE

This review summarizes recent advances that have helped clarify the process of malignant transformation in cutaneous tumors.

RESULTS

Ultraviolet radiation-induced mutations in the p53 tumor suppressor gene and human papilloma virus inhibition of the p53 and retinoblastoma tumor suppressor gene products appear to play significant roles in the development of many cutaneous squamous cell carcinomas. Studies of patients with the nevoid basal cell carcinoma syndrome suggest the existence of an additional regulatory gene that may be involved in the development of basal cell carcinomas.

CONCLUSIONS

Carcinogenesis is multistep process involving genetic and epigenetic alterations to specific proto-oncogene and tumor suppressor gene products that progressively release the cell from normal controlled growth and replication.

Genotypic classification of colorectal adenocarcinoma. Biologic behavior correlates with K-ras-2 mutation type

BACKGROUND

New measures enabling better prediction of biologic behavior of large bowel cancer are highly desirable. One hundred ninety-four consecutive primary, recurrent, and metastatic colorectal adenocarcinomas, accessioned during 1991 at Rhode Island Hospital, were classified according to the presence and specific type of K-ras-2 point mutation.

METHODS

An integrated histopathologic-genetic approach was used to detect mutations starting with minute, topographically selected, tissue samples from formaldehyde-fixed, paraffin-embedded specimens.

RESULTS

Each colorectal adenocarcinoma exhibited either no or only one of seven specific types of K-ras-2 mutation. The mutation type of each primary tumor was present consistently in its metastatic deposits. Thirty-five percent of primary colorectal adenocarcinomas were found to be mutated (42 of 119). A significantly higher mutation rate (65%) was seen in lymphogenous-hematogenous metastases as a group (35 of 54; P < 0.005). By contrast, 22% of anastomotic recurrences and transcoelomic metastasis were mutated (4 of 18). Twenty-eight percent of adenocarcinomas with invasion limited to muscularis propria (Tis, T1, T2) were mutated (16 of 57), compared to 41% for more deeply invasive tumors (T3, T4; 26 of 63). When colorectal adenocarcinomas were analyzed by specific K-ras-2 mutation type, it was found that codon 13 mutated tumors did not progress to local or distant metastasis (P < 0.01). Tumors having a codon 12 valine substitution did not metastasize beyond pericolonic-perirectal lymph nodes. In contrast, colorectal cancers with codon 12 aspartic acid substitutions accounted for most of the distant hematogenous deposits (P < 0.01). Tumors with normal K-ras-2 accounted for most intraperitoneal deposits.

CONCLUSIONS

Genotyping of colorectal adenocarcinoma by K-ras-2 status can identify subsets of patients likely to pursue indolent and aggressive forms of disease. The integrated histopathologic-genetic approach outlined is feasible for use in diagnostic pathology, providing information that together with clinicopathologic staging may individualize and optimize treatment.

Oncogenes: present status

Oncogenes are genes associated with causation of cancer. They were originally associated with the ability of retroviruses to cause tumors in animals. These viral oncogenes (V-onc) have their cellular counterparts (C-onc) called Proto oncogenes. Function of Proto oncogenes is to maintain cellular growth and development. Activation of these proto-oncogenes can occur due to mutation which leads to uncontrolled cell growth. The Proto oncogenes can be grouped into different categories based on their protein products, i.e. protein kinases, growth factors, growth factor receptors, and DNA binding proteins. There are also genes that normally suppress malignant transformation and these are called anti oncogenes. Loss of their suppressor activity leads to unimpeded growth. Oncogene abnormalities are seen in pediatric leukemias, lymphomas, and various solid tumors. Anti oncogenes are associated with retinoblastoma (Rb gene), Wilms' tumor, rhabdomyosarcoma and neuroblastoma, etc. Identification of these abnormalities have diagnostic, prognostic and therapeutic implications. The utility of oncogenes in classification of human cancer and monitoring cancer therapy is quite clear, but the future of these for therapeutic interventions remains uncertain. Role of c-abl oncogene in chronic myeloid leukemia (CML), bcl-2, in lymphomas, N-myc in neuroblastomas and retinoblastoma (Rb) gene in retinoblastomas is well understood and used in designing proper therapeutic approaches. Since oncogenes also control normal cellular function, their use for therapy may be limited by the amount of damage to normal cells. Their maximum therapeutic benefit may be realized only when used in combination with other modalities.

Nuclear roundness factor and local failure from definitive radiation therapy for prostatic carcinoma

Of 375 patients with prostatic carcinoma treated definitively with radiation therapy at this institution with at least a 5 year follow-up, 23 patients failed locally only, 72 failed with distant metastasis only, 60 had both local and distant failure, while 220 showed no evidence of disease. In search for a possible marker for local failure following radiation therapy, we examined several nuclear morphometric parameters which have been shown to correlate with the biologic aggressiveness of this disease. The 23 locally failed only patients were matched with 23 no evidence of disease patients for stage, grade, treatment modality, prior surgery, age at diagnosis and race. Archival hematoxylin and eosin slides were obtained for 22 of the 23 matched pairs, and morphometric features, including nuclear roundness factor and nuclear area, as well as numbers of nucleoli were assessed using computer-assisted image analysis in both tumor cells and normal prostatic epithelium. Tumor nuclei from the locally failed only patients had significantly higher nuclear roundness factor values (p = 0.0089) compared with tumor cells from no evidence of disease patients. Analysis of these data by clinical stage demonstrated no significant differences between the locally failed only and no evidence of disease patients. Likewise, there were no significant differences in nuclear roundness factor values of locally failed only and no evidence of disease patients with poorly or moderately well-differentiated tumors. However, there was a highly significant difference (p = 0.0012) in the nuclear roundness factor values of locally failed only and no evidence of disease patients with well-differentiated tumors. Thus, there appears to be a subset of patients with well-differentiated adenocarcinoma of the prostate who have significantly more irregular tumor nuclei and who fail locally only following definitive radiation therapy.