Touch imprint smear: A prerequisite to obtain better quality and "true" tumor RNA in breast tissues

Abstract

Background: RNA is the primary genetic material required for various molecular studies. RNA derived from breast tissue has low quality and quantity compared to that extracted from other tissues. Therefore, optimization of techniques for breast tissue RNA extraction is a challenging but essential requirement.

Methods: RNA was extracted from 60 samples of breast cancer after dividing them into 2 groups. Each tissue was divided into 2 halves for RNA extraction and histopathology respectively. In group 2 RNA was extracted after taking touch imprints whereas group1 was not subjected to any such procedure. Concentration and purity of RNA was assessed by using spectrophotometer and 1% agarose gel followed by RT-PCR for 18 S rRNA and CCND1 gene.

Results: Based on microscopic observations of imprints, group 2 samples were further subdivided into 2 subgroups. Group 2 A (n = 30) showing tumor in imprint smears were found to yield best concentration of pure RNA (1846.50 ng/µl and 1.92) as compared to group 2B (n = 15) with no malignancy in imprints (102.61 ng/µl and 1.53). The correlation of imprint smears with their corresponding H&E-stained slides further leads to grouping of each group in 2 groups. RT-PCR analyses showed better melting peaks and high relative expression of CCND1 in group 2 A.

Conclusion: Touch imprints may provide valuable information regarding presence or absence of tumor in tissue samples being used for extraction of genetic material. This approach can be used as easy, cheap and fast strategy to resolve the doubts associated with RNA being truly representative of the tumor.

Keywords: RNA concentration; RNA extraction; RT-PCR; Tumor imprints.