Immunohistochemical markers in the diagnosis of precancerous lesions of the oral mucosa and red border of the lips

Timely and effective diagnosis of neoplastic lesions of the oral mucosa (CRS) and red lip rim (CCG) remains a serious problem of oncostomatology. Squamous cell carcinoma of the oral cavity occupies the sixth place in the world in frequency among malignant tumors of all localizations. In the Russian Federation, the incidence of malignant neoplasms of the oral cavity is 2-4% of the total number of malignant tumors of man.

In recent years, the structure of diseases of the oral mucosa has undergone significant changes, in particular, an increase in the proportion of precancerous diseases. In this regard, the effective non-invasive detection of signs of malignancy remains an urgent task of dentistry.

Despite the seeming simplicity of the clinical visualization of predictor changes in the oral mucosa and CCG due to external localization, the determination of the nosological form of the precancer, based only on the impression of examination and palpation, often leads to diagnostic errors, since different degrees of keratinization or ulceration of even marker elements defeat makes them difficult to differentiate. Especially difficult is the early diagnosis of malignancy, because its clinical signs appear a little later than the actual malignant transformation.

Thus, the research of V.P. Kharchenko et al. It is shown that more than 2/3 of patients at the time of treatment in the medical institution and the establishment of the diagnosis have III-IV stages of the disease. One of the reasons for late treatment is the "blurring" of the clinical picture at the initial stages of the disease. In addition, the need to conduct organizational and methodological work and increase the level of knowledge of dentists about the early clinical manifestations of precancerous diseases of the oral mucosa has been proved. The conducted testing showed that only 42.8% of dentists differentiate the early manifestations of oral cancer, 4.2% of the respondents can correctly carry out primary diagnostic measures for the detection of cancer of this localization.

The percentage of incurable forms of cancer of the oral mucosa due to diagnostic errors, according to different authors, reaches 58.4-70%. The situation is complicated by the unresolved issues of clinical diagnosis of precancer, especially the difficulty of differentiating the onset of malignancy, as well as the problem of choosing a method for treating a pre-tumor disease. There are no absolute and relative indications for biopsy, especially at the stages of conservative treatment. To date, there is not a single example in the literature of the diagnostic criterion of the clinical level that a dentist could refer to when choosing an appropriate method for treating a particular pre-tumor disease.

Resolution of diagnostic difficulties most authors see in auxiliary diagnostic methods (cytology, cheilostomatoscopy, biomicroscopy, optical coherence tomography). However, these methods are rather subjective, since they bear only the descriptive nature of qualitative changes in the affected tissues. One way to quantify morphological changes is to determine immunohistochemical markers.

The introduction into modern practice of modern morphological methods of tumor verification has significantly improved the quality of diagnosis and treatment of malignant tumors. The methodological possibilities of modern molecular oncology have expanded, at present, with the help of immunohistochemical research, it is possible to establish not only a histological diagnosis of a tumor, but also to give it a morphofunctional characterization from the point of view of aggressiveness and prognosis regarding precancerous lesion and an already developed oncological disease.

According to modern ideas, the basis of malignant transformation of cells is the activation of single or multiple cellular oncogenes or suppressor genes. It is observed in 30% of human cancer cancers and in many cases can be detected immunohistochemically. Oncogenes ras p21, HER2 / neu, bcl-2 and suppressor genes p53 and Rb in various tumors have been studied. Some of the listed oncogenes (and suppressor genes) are independent prognostic and predictive signs.

The epithelium of the oral mucosa is the locus praedifectionis of the formation of cancerous tumors. External factors (traumatic nodes of occlusion, acute edges of restorations, untenable orthopedic constructions, irrational individual hygiene of the oral cavity, inflammatory-destructive periodontal lesions) along with genetic (hereditary) factors can play a determining role in the occurrence of cancer of this localization. In the development of squamous cell carcinoma of the oral mucosa, damage can be involved in the mechanisms controlling the processes of epithelial hyperplasia and squamous cell metaplasia.

Morphological features of the epithelium of the oral mucosa during the malignancy are associated with a change in the set of differentiation markers (primarily the cytokeratin phenotype of the epithelial layer), CEA expression, and Ki - 67 proliferation markers.

P53 is a tumor suppressor gene, the protein product of which is a nuclear transcription factor with many functions, including blocking the passage of cells through the cell cycle and induction of apoptosis. The p53 protein is expressed in all cells of the body. In the absence of damage to the genetic apparatus, the p53 protein is in an inactive state, and when DNA damage occurs, the DNA is activated. Activation consists in acquiring the ability to bind to DNA and activate transcription of genes that contain a nucleotide sequence in the regulatory region, which is denoted by the p53-response element. The p53 mutation, found in cells of about 50% of cancerous tumors, leads to protein synthesis with the loss of its functions, but which is highly stable and accumulates in the nucleus, which is immunohistochemically expressed in distinct nuclear staining.

The "wild" type of the wt-53 oncosuppressor gene and the p53 protein coded by it play a central role in the development of apoptosis. When DNA is damaged, expression of the wt53 gene and the corresponding protein occurs. The latter blocks the cell cycle in the G1-S phase and thereby inhibits further replication of the damaged DNA, which is synthesized in the S phase, and creates conditions for the removal of the damaged site and repair of its altered site. If reparation occurs, the cell continues to divide and give generation of healthy cells. However, if reparation does not occur, then other mechanisms are included that ensure the destruction of such a cell with damaged (mutagenic) DNA, i.e. The genetic program of cell death is developing - apoptosis.
In recent years, it has been suggested that p53-status can be a decisive factor determining the sensitivity of a tumor to chemo- and radiotherapy. Confirmation of this assumption are numerous studies proving that mutated p53 is a factor of poor prognosis and ineffectiveness of adjuvant therapy for a variety of neoplasms of the oral mucosa.

Markers of proliferation are also a highly informative diagnostic value in predicting the course of malignant tumors. Proliferative activity is a leading factor both in the mechanism of malignant transformation of cells, and in the biological behavior of already emerging tumors. A promising marker of proliferative activity is the Ki-67 antigen, which is expressed practically in all phases of the cell cycle and, accordingly, reflects the magnitude of the proliferative pool. The gene encoding Ki-67 is located on the long arm of the 10 chromosome. Ki-67 refers to regulatory proteins. Its appearance coincides with the entry of the cell into mitosis, which makes it possible to use it as a universal marker of proliferation in evaluating the growth of malignant tumors.

A number of studies have been carried out that study the diagnostic value of immunohistochemical markers in predicting the course of precancerous lesions of the oral mucosa and the red border of the lips. Murti PR et al. Studied the expression of p53 with red flat-rate SSRI. When the immunohistochemical method was determined, expression of p53 failed to reveal the malignant status of the precancer of the oral mucosa. The authors suggested that the peak of overexpression of p53 is close to the time of transformation of the precancer into cancer, and can not be used as an early marker for predicting the malignancy of the precancer of the oral mucosa. Other researchers found that the human gene TP53 encodes at least 9 different isoforms. Another member of the p53 family, p63, includes 6 different isoforms and plays a key role in the development of the oral mucosa, salivary glands, teeth and skin. It was suggested that p63 is associated with the development of squamous cell carcinoma of the head and neck. However, no statistically significant changes in the expression of new isoforms of p53 and p63 in the precancer of SSRI were observed in comparison with unmodified tissue. Studies by De Sousa FA confirmed the prognostic significance of the p53 marker in determining the potential of malignant transformation of the precancer of the oral mucosa. At the same time, some authors believe that p53 can not be used as a single marker for predicting the development of cancer.

No less promising in the prognostic plan is the immunohistochemical detection in the samples of the examined tissues of the subplane - the integral membrane mucoprotein expressed both by the unmodified and inflammatory-altered and neoplastic endothelium of lymphatic capillaries. The researchers found a statistically significant relationship between the expression of sub-planin and ABCG2 (ATP-binding protein, subgroup G2) with the risk of malignant transformation of red flat lichen (the risk was significantly higher with co-expression of the sub-planin and ABCG2 than without coexpression of the sub-planin and ABCG2) and concluded that the sub- ABCG2 can be used as biomarkers to assess the risk of malignant transformation in precancerous lesions of SAD

Researches of foreign scientists confirmed the diagnostic significance of Fas / FasL expression as biomarkers of cancer development. Fas is type I transmembrane glycoprotein (synonyms APO-I, CD95) and induces apoptosis in the cell after interaction with Fas ligand (FasL) or agonistic monoclonal antibodies against Fas.

At the same time, it is known that Fas is expressed in virtually all types of tissues. Increased Fas expression is observed in the kidneys, liver, heart and thymus. In addition, this receptor is expressed on many tumors, as well as virus-infected cells. The reason for the resistance of different cell types to Fas-dependent apoptosis may be increased production of soluble Fas by these cells. Soluble Fas is a product of alternative splicing and is able to inhibit apoptosis induced by agonistic monoclonal antibodies against Fas or FasL.

Thus, the ambiguous interpretation of the results of the conducted studies by different authors allows us to conclude that at the present stage of development of molecular oncology the use of immunohistochemical markers is promising in combination with other methods of diagnosis and prediction of the course of precancerous lesions of the oral mucosa.

Of particular relevance is the problem of ranking immunohistochemical markers for diagnostic significance. We believe that, in order of decreasing importance, they can be arranged in the following order:

1. Immunohistochemical markers of high diagnostic significance: subplanin, ABCG2, bcl-2;
2. Immunohistochemical markers of an average degree of diagnostic significance: Bax, MMP-9;
3. Promising immunohistochemical markers, the diagnostic significance of which requires further study: MMP-2, MT1-MMP, Fas / FasL;
4. Immunohistochemical markers, the diagnostic significance of which to predict the course of precancerous diseases is not proved: p53, p63.

Based on the analysis of published data, it can be concluded that the definition of immunohistochemical markers should not be considered as the only method for predicting the course of precancerous diseases of the oral mucosa and detecting the risk of malignant transformation, but nevertheless the method has high diagnostic value when combined with other methods of predicting the course of precancerous diseases.

Senior Researcher Kuznetsova Roza Gilevna. Immunohistochemical markers in the diagnosis of precancerous lesions of the mucous membrane of the mouth and the red border of the lips // Practical medicine. 8 (64) December 2012 / volume 1

[1], [2], [3], [4], [5]