p53 immunostaining is correlated with reduced survival and is not correlated with gene mutations in resected pulmonary large cell carcinomas

Prognostic Significance of p53 Protein and X-ray Repair Cross-Complementing Protein 1 in Non-Small Cell Lung Cancer

Objectives

p53 and XRCC1 protein expression were evaluated in 54 samples of non-small cell lung cancer.

Patients and methods

The immunohistochemical method was used for detection of the monitored proteins. Tissue samples were divided according to histopathological tumor type. The results were then compared with basic clinical and histopathological parameters (histopathological type, nuclear grade and TNM tumor stage IA, IB).

Results

Statistically significant correlations were found between histopathological type and p53 expression, since P <0.05 (P = 0.015). Comparing p53 expression with grade resulted in a strong positive correlation (P <0.0396, R2 = 0.9223). The percentage of p53-positive tumors progressively increased from 0% in grade 1 to 75% in grade 4. No correlation was found between p53 expression and tumor stage. In case of XRCC1, the highest level was found in squamous cell lung carcinoma, where 71% of samples was positive. In case of large cell carcinoma samples, it was 67%, and in adenocarcinoma 52% of samples showed XRCC1 immunoreactivity. No statistically significant correlation was found between histopathological type, grade or early stage (IA, IB) of non-small cell lung cancer and expression of XRCC1 protein profile without neoadjuvant therapy.

Conclusions

We found a statistically significant correlation between p53 expression and histopathological tumor type. It is possible that stabilized p53 protein plays an important role in the development of squamous and large cell carcinoma. Our findings also suggest that p53 expression cumulates with the dedifferentiation of cancer cells. It is possible that the expression of XRCC1 is not fixed and could be changed by the status of cancer cells and in relation to therapy. Relevant data about pre- versus post-chemotherapy and XRCC1 expression are needed to evaluate the influence of XRCC1 on drug resistance. Free full text available at www.tumorionline.it

p16INK4A and p14ARF tumor suppressor pathways are deregulated in malignant rhabdoid tumors

Malignant rhabdoid tumors (MRTs) are aggressive tumors associated with mutations in the SMARCB1 gene. In experimental systems, the loss of SMARCB1 is hypothesized to alter p16(INK4A) pathways resulting in the repression of tumor suppressors. To determine whether these pathways are deregulated in human MRT, we used immunohistochemistry on tissue microarrays to evaluate p16(INK4A)/E2F1/RB and p14(ARF)/MDM2/p53 pathways in 25 atypical teratoid/rhabdoid tumors (AT/RT) and 11 non-CNS MRT. p16(INK4A) was negative or showed focal weak expression. p16(INK4A) downstream targets CDK4/cyclin D1/ppRB were variably expressed at moderate to low levels; E2F1 was negative. Unexpectedly, p14(ARF) expression was seen in many cases, which correlated positively with p53 and inversely with MDM2 immunostaining in AT/RT. TP53 mutational analysis in 19 of 25 AT/RT and in 8 of 11 non-CNS MRT cases showed point mutations in only 3 AT/RT cases, suggesting that p53 expression was driven mainly by p14(ARF). Finally, nucleophosmin, a protein that stabilizes p53, was positive in most cases and colocalized with p53. Together, these data suggest that, in MRT, there is deregulation not only of p16(INK4A) but also of the p14(ARF) pathway. These results provide insights into cell cycle deregulation in the pathogenesis of human MRT and may aid in the design and evaluation of potential therapies for these tumors.

Role of immunohistochemistry in the diagnosis of lung cancer

The role of immunohistochemistry is to recognize antigens and, consequently, to identify and classify specific cells within a cell population whose morphology is heterogenous or apparently homogenous. The visualization of the antigen-antibody complex is made possible through the addition of either a fluorochrome conjugate or an enzyme to the antibody, which is then viewed under microscopy. Immunohistochemistry can be used in the routine diagnosis of lung cancer, in order to identify biological markers (diagnostic and prognostic). The essential immunohistochemistry panels will be discussed in this review.