Prognostic significance of DNA cytometry in combination with AgNOR investigation

Nucleolar and Ribosomal DNA Structure under Stress: Yeast Lessons for Aging and Cancer

Once thought a mere ribosome factory, the nucleolus has been viewed in recent years as an extremely sensitive gauge of diverse cellular stresses. Emerging concepts in nucleolar biology include the nucleolar stress response (NSR), whereby a series of cell insults have a special impact on the nucleolus. These insults include, among others, ultra-violet radiation (UV), nutrient deprivation, hypoxia and thermal stress. While these stresses might influence nucleolar biology directly or indirectly, other perturbances whose origin resides in the nucleolar biology also trigger nucleolar and systemic stress responses. Among the latter, we find mutations in nucleolar and ribosomal proteins, ribosomal RNA (rRNA) processing inhibitors and ribosomal DNA (rDNA) transcription inhibition. The p53 protein also mediates NSR, leading ultimately to cell cycle arrest, apoptosis, senescence or differentiation. Hence, NSR is gaining importance in cancer biology. The nucleolar size and ribosome biogenesis, and how they connect with the Target of Rapamycin (TOR) signalling pathway, are also becoming important in the biology of aging and cancer. Simple model organisms like the budding yeast Saccharomyces cerevisiae, easy to manipulate genetically, are useful in order to study nucleolar and rDNA structure and their relationship with stress. In this review, we summarize the most important findings related to this topic.

Histologic grading and nucleolar organizer regions in oral squamous cell carcinomas

Objective

The purposes of this study were to histologically assess different types of oral squamous cell carcinoma and the silver-binding nucleolar organizer region (AgNOR) morphology in neoplastic cells, as well as to quantify the number of AgNORs in each type of carcinoma in order to relate AgNOR count and histologic grading.

Material and Methods

Twenty-eight cases of oral squamous cell carcinoma were divided into 4 groups, namely well-differentiated, moderately differentiated, poorly differentiated, and undifferentiated. For NOR study, 3-µm-thick sections were stained with 50% aqueous silver nitrate solution. The predominant microscopic pattern of NORs was determined. Quantitative analyses of NORs were obtained of all cells present on each histological field using a 0.025 mm² eyepiece graticule. Different histological fields were analyzed until the total number of NORs was 120 cells for each tumor. Kruskall-Wallis test was applied to compare the groups of sample data at a significance level of p=0.05.

Results

The mean number of AgNORs per nucleus was 3.20 for the well-differentiated group, 5.33 for the moderately differentiated one, 8.27 for the poorly differentiated one, and 10.08 for the undifferentiated one. AgNOR count was significantly different (p<0.05) among all of the studied groups.

Conclusion

AgNOR staining technique seems to be a useful diagnostic tool since differences in AgNOR numeric values can be identified in the different types of oral squamous cell carcinoma. This technique is easy to handle and inexpensive, thus justifying its large use in histopathology.

Heterogeneity of DNA content in laryngeal squamous cell carcinoma in relation to histopathological variables

CONCLUSION

Multivariate analysis showed age, lymph node status, proliferative index in transformation border, and DNA index in the center of laryngeal squamous cell carcinoma to be significant predictors for survival. By accessing distinctive areas of the tumor we were able to reduce the impact of intratumoral heterogeneity on prognostic factors.

OBJECTIVES

Laryngeal carcinomas are characterized by considerable histological variation within the tumor. The possible effects of this morphological heterogeneity on the estimation of tumor DNA content were investigated.

MATERIALS AND METHODS

We analyzed 92 cases of archived, paraffin-embedded laryngeal carcinoma. For each tumor, three different regions, defined microscopically (center of tumor, transformation border, invasive border), were analyzed. DNA content was measured by flow cytometry. Three parameters were evaluated: DNA ploidy, DNA index, and proliferative index.

RESULTS

DNA ploidy, DNA index, and proliferative index were higher in the tumor center than in the respective borders. Intratumoral differences in DNA ploidy were observed in 56 tumors (60.8%); DNA index heterogeneity was observed in 57.6% cases. Proliferative index varied greatly in morphologically different parts of the same carcinoma. DNA ploidy and DNA index of the transformation border correlated with tumor size and lymph node status. Proliferative index of the tumor center and of transformation border correlated with lymph node status, tumor size, and histological grade.