Immunohistochemical expression of cyclin T1 in a case of AIDS-related cachexia.

The expression of cyclin T1 in an autoptic case of AIDS-related cachexia was investigated by immunohistochemistry. When contrasted with normal human tissues, a very similar pattern of expression was found. However, a peculiar distribution of cyclin T1 was noticed in the brown fat and in lymph nodes affected by AIDS-associated lymphadenopathy.

Expression of the retinoblastoma-related p107 and Rb2/p130 genes in human placenta: an immunohistochemical study.

It has been proposed that tumor suppressor genes may have a role in the mechanisms of proliferation and differentiation during human placental development. The Retinoblastoma gene family is a well known family of tumor suppressor genes. Many studies have pointed out a role of this family not only in cell cycle progression, but also during development and differentiation. On the light of these observations we have investigated the immunohistochemical expression pattern of the Retinoblastoma family members, p107 and Rb2/p130 in human placenta samples in first trimester and full-term placental sections. p107 and pRb2/p130 showed the most abundant expression levels during the first trimester of gestation and progressively declined to being barely detectable in the placenta by late gestation. These results indicate that the expression of the above genes is modulated during placental development and suggest a mechanism for controlling trophoblast proliferation.

Pattern of expression of cyclin T1 in human tissues.

Cyclin T1 was recently identified, together with cdk9 (previously named PITALRE), as part of the TAK multiprotein complex, a co-factor targeted by the human immunodeficiency virus Type 1 (HIV-1) protein named Tat, suggesting a role for this complex in transcription elongation. Although studies on mRNA and protein expression have shown that cyclin T1 is ubiquitous in adult human tissues, no data have yet been reported regarding the expression of this protein in different cell lineages. Using a polyclonal antiserum raised against cyclin T1, we investigated the pattern of expression of this protein in adult human tissues by immunohistochemistry. Cyclin T1 was expressed ubiquitously, although different levels of expression were found in various organs. Some specialized tissues, such as blood, lymphoid tissues, and cells of connective tissue origin, showed high cyclin T1 expression. These specific expression patterns are only partially justified by some well-known specialized functions of cyclin T1 in certain cell types, such as its involvement in peripheral blood lymphocytes and monocyte differentiation. The high expression level found in other tissues suggests new possible roles for cyclin T1 in cell types other than those of lymphoid tissue.

Cyclin T2a gene maps on human chromosome 2q21.

Cyclin T2a was recently identified as one of the regulatory subunits of the cdk-cyclin complex P-TEFb, the most studied positive factor in the regulation of transcription elongation. By fluorescent in situ hybridization (FISH), the gene codifying for cyclin T2a has been mapped on human chromosome 2q21. This locus also has been linked to different forms of myopathy. By use of a new specific antiserum raised against cyclin T2a, the immunohistochemical pattern of expression of cyclin T2a in human tissues has been examined and compared to that of cyclin T1, described in the previous report. The observation that immunohistochemical expression of cyclin T2a was high in skeletal muscle cells, whereas it was undetectable in two cases of centronuclear myopathy, together with its chromosomal location, suggests an involvement of the cdk9-cyclin T2a complex in this disease.

Alteration of the Bcl-2:Bax ratio in the placenta as pregnancy proceeds.

The placenta is the primary site of nutrient and gas exchange between mother and foetus. During human placental development, proliferation, differentiation and apoptosis occur at different stages. In order to clarify some of the molecular mechanisms underlying these events, we investigated the pattern of expression of two members of the Bcl-2 family in human placenta samples and compared them to the level of apoptosis detected by the TUNEL method. In particular, we evaluated the expression of Bcl-2 and Bax and their ratio during the first and third trimester. We found that Bcl-2 was generally expressed at low levels during the entire gestational period. On the other hand, Bax was low during the first trimester but increased towards the end of gestation. In accordance with the change of ratio of these two molecules, the increase of apoptotic cells was observable in the third trimester. These data indicate that Bcl-2 and Bax are spatio-temporally regulated during placental development and that the different expression of the above mentioned genes is at least in part responsible for the delicate balance between cell proliferation and programmed cell death in the human placenta during pregnancy.

Prognostic role of cyclin D1 in non small cell lung cancer: an immunohistochemical analysis.

Lung cancer is a worldwide problem and in many countires it is the most lethal malignancy. Because relapse is frequent after resection of non small cell lung cancer, an urgent need exists to define prognostic factors which could help in choosing the best therapeutic approach. We performed immunohistochemistry on 60 formalin-fixed paraffin-embedded non small cell lung cancer specimens in order to evaluate the frequency of cyclin D1 overexpression, and to relate it to the degree of malignancy of these tumors and to the overall survival time of the patients. All specimens were positive for cyclin D1 immunostaining. We found cyclin D1 overexpression in 30 (50%) of our specimens, with no significant difference among the different histological types. Cyclin D1 overexpression correlates in a statistical manner with short-term patient survival. Mantel-Cox analysis of these data generated a significant P value = 0.003. The mean survival time and the five-year survival rate also differed statistically. We did not find any statistically significant correlation between cyclin D1 overexpression and histological grading, tumor stage or TNM status. We concluded that cyclin D1 overexpression in 30 patients is a frequent event in non small cell lung cancer pathogenesis and may have prognostic relevance.

Altered expression of p53 and Rb tumor suppressor genes in lung cancer.

The aim of this study was to evaluate the frequency of altered expression of pRb and p53, two well known tumor suppressor genes, in lung cancer and to relate it to the prognosis of the patients affected by this type of neoplasm. We evaluated 68 specimens from patients with surgically resected lung cancer. Of the 68 neoplasms investigated, 29 (42.6%) displayed a positive nuclear staining for p53. Ten (15.7%) of the investigated tumors showed absence of pRb nuclear immunoreactivity. p53 overexpression correlated statistically with short-term survival. On the other hand no statistically significant difference (p=ns) in survival was detected between pRb producers and nonproducer patients. In addition, we divided our specimens into two groups according to the p53 and pRb status. The first group consisted of all the p53(+) pRb specimens. The second group contained all the remaining specimens. Comparison between these two groups did not reveal any significant difference in overall survival time. These findings confirm that only p53 overexpression can be considered an independent prognostic factor in lung cancer.