At present, tumor-adjacent tissue samples are considered as normal specimens and normal controls in histopathological applications, and therefore often used as a standard negative control to determine whether malignant tumors have been removed cleanly . However, we cannot guarantee that normal tissue adjacent to cancerous tissue (NTAC) has been unaffected by the nearby malignant tumor. Normal tissue adjacent to benign tissue (NTAB) has been shown to be histologically and genetically normal, but the issue of distinguishing one from the other in a reliable manner has continued to elude researchers.
A growing tumor body surrounded by pathologist-validated NTAC is by definition abnormal at the molecular level because of long-term expansion or clonal conversion from patch to field of cancerization [1–4]. Those two models have been implicated mainly in malignant tumors of the breast, skin, prostate, lung, liver, brain and gastrointestinal tract [4–9]. However, wound-healing does not occur in tissues adjacent to invasive cancers . The epithelial-mesenchymal transition that initiates the invasion process of most tumors has also been observed in NTAC [11, 12]. Moreover, diverse genetic studies of field cancerization have assessed the copy number, expression and single nucleotide polymorphisms in the genomic DNA and messenger RNA of NTAC, but they cannot explain the mechanisms behind tumor progression, metastasis or recurrence [2, 13, 14]. The genetic alterations between NTAC and NTAB may provide new insight into the field of cancerization and tumor transformation.
Tumor development is a smooth process that goes through several molecular stages, including gene transformation [15, 16]. Tumor cells interact with adjacent normal cells, indicating gene cross-talk and mutual signal transduction from the two kinds of cells [15, 17–19]. Relative to benign tumor cells, malignant tumor cells show more aggressive cellular growth and integration. Thus, we could expect that benign and malignant tumors and their adjacent tissues would undergo different malignant transformations.
The genes that initiate tumor processes are collectively known as tumor-related genes (TRGs) and comprise oncogenes, tumor-suppressor genes, and genes that promote and inhibit cancer progression and metastasis. To date, many TRGs from malignant tumors and other cells have been identified and intensively studied for the purposes of explaining the molecular mechanism of cancer development, drug discovery and diagnostics [16, 20, 21]. Nevertheless, few clinical studies have been specifically devoted to the rule of TRGs in distinguishing NTAC from NTAB.
In this study, we collected tumors that were malignant (six types) and benign (two types) and adjacent tissue samples (eight types) from 314 patients to generate a tumor microarray (TMA). We then used 15 histogenetic cancer markers, or TRGs (MYC (ENSG00000136997), CCND1 (ENSG00000110092), TP53 (ENSG00000141510), UVRAG (ENSG00000171862), RB1 (ENSG00000139687), PTEN (ENSG00000171862), PTCH1 (ENSG00000185920), BRCA1 (ENSG00000012048), BRCA2 (ENSG00000139618), FHIT (ENSG00000189283), BECN1 (ENSG00000126581), BCL10 (ENSG 00000142867), APC (ENSG00000134982), CD82 (ENSG00000085117) and NME1-NME2 (ENSG 00000011052)) for finding novel biomarkers involved in cancerization or tumor transformation or recurrence through RNA in situ hybridization (RISH) and comprehensive statistical analysis.