[The structure of pathogenic germline variants in colorectal cancer in Moscow patients]. / Struktura patogennykh germinal'nykh variantov pri kolorektal'nom rake v vyborke patsientov Moskvy.

OBJECTIVE: Describe the structure of pathogenic germline variants and clinical and anatomical features in colorectal cancer patients in Moscow. MATERIAL AND METHODS: The whole genome sequencing results of patients with suspected hereditary cancer syndrome were evaluated. All identified genetic variants were validated using Sanger sequencing. RESULTS: The study included 238 patients with colorectal cancer, 41/238 (17.2%) patients have pathogenic germline variants associated with hereditary cancer syndromes or increased cancer risk. Lynch syndrome accounts for 8% of all colorectal cancer cases (19/238), and familial adenomatous polyposis - 1.7% (4/238). 5 new genetic variants were described for the first time in a Russian colorectal cancer patients: MLH1 c.1921dup (p.Leu641fs), APC c.2929C>T (p.Gln977Ter), PMS2 c.327del (p.Ala110LeufsTer2), MSH2 c.1857dup (p. Val620CysfsTer24), ATM c.895G>T (p.Glu299Ter). In 197 of 238 patients, no significant variants were identified or variants with an uncertain clinical underlying cause were identified. CONCLUSION: According to the results of the study, an earlier manifestation of a malignant neoplasm and a more frequent occurrence of high-grade carcinomas in the presence of pathogenic germline mutations were noted compared to the group of patients without clinically significant varianrs, while in the group with identified mutations, the frequency of regional and distant metastasis was not increased.

[Epigenetic Regulation Disturbances on Gene Expression in Imprinting Diseases].

Epigenetic regulation is hereditary and non-hereditary changes in the expression of a particular gene without any corresponding structural changes in its nucleotide sequence. Genomic imprinting is an epigenetic mechanism for regulating the expression of homologous genes depending on parental origin, i.e., they are expressed monoallelically in the mammalian diploid cell. Being genetically imprinted, only the maternal or only the paternal genome is unable to ensure normal embryonic development. The most studied epigenetic modification, which plays one of the main roles in the maintenance of imprinting processes, is the specific methylation of cytosine in CpG-dinucleotides. All known imprinted genes contain differential DNA methylation regions on homologous parent chromosomes, which are necessary for their monoallelic expression. However, it is now known that not only DNA methylation, but chromatin remodeling, histone modifications, and non-coding RNAs also ensure the proper functioning of imprinted genes in the human body. Structural and functional disturbances of epigenetic mechanisms lead to imprinting diseases.

Inactivation of Epigenetic Regulators due to Mutations in Solid Tumors.

Main factors involved in carcinogenesis are associated with somatic mutations in oncogenes and tumor suppressor genes representing changes in the DNA nucleotide sequence. Epigenetic changes, such as aberrant DNA methylation, modifications of histone proteins, and chromatin remodeling, are equally important in the development of human neoplasms. From this perspective, mutations in the genes encoding key participants of epigenetic regulation are of particular interest including enzymes that methylate/demethylate DNA, enzymes that covalently attach or remove regulatory signals from histones, components of nucleosome remodeling multiprotein complexes, auxiliary proteins and cofactors of the above-mentioned molecules. This review describes both germline and somatic mutations in the key epigenetic regulators with emphasis on the latter ones in the solid human tumors, as well as considers functional consequences of these mutations on the cellular level. In addition, clinical associations of the somatic mutations in epigenetic regulators are presented, as well as DNA diagnostics of hereditary cancer syndromes due to germline mutations in the SMARC proteins and chemotherapy drugs directly affecting the altered epigenetic mechanisms for treatment of patients with solid neoplasms. The review is intended for a wide range of molecular biologists, geneticists, oncologists, and associated specialists.

[The incidence of AZF deletions, CFTR mutations and long alleles of the ar CAG repeats during the primary laboratory diagnostics in a heterogeneous group of infertily men].

AIM: microdeletions in the AZF region of Y-chromosome, compound heterozygotes of severe and mild CFTR mutations, and long CAG-repeats in the androgen receptor gene (AR) as marker of predisposition are frequently studied as genetic causes of male infertility. A simultaneously testing of the panel including biochemical, immunological, cyto- and molecular genetic markers is often performed during the complex laboratory diagnostics in infertile men. The aim of our work was to identify molecular genetic alterations, which are advisable for simultaneously testing in a man with currently uncertain form of infertility, to increase the informativeness of laboratory diagnostics. MATERIALS AND METHODS: a retrospective study of 885 infertile men was conducted. AZF deletions were determined by multiplex PCR using 10 STS-markers (sY83, sY84, sY86, sY127, sY134, sY143, sY152, sY157, sY254, sY255) and two control loci SRY and AMEL with detection in polyacrylamide gel. Mutations in the CFTR gene (F508del, CFTRdel2.3(21kb), I507del, 1677delTA, 2143delT, 2184insA, 394delTT, W1282X, G542X, N1303K, R334W and 5T) were detected by PCR and SNaPshot. For determination of length of the AR CAG-repeat a fragment analysis of fluorescently labeled PCR products on the 3500xl capillary sequencer was performed. RESULTS: AZF deletions were detected in 8.2% of cases. The largest number of deletions was found in the AZFc subregion (58.9%), while a frequency of deletion in AZFa, AZFb or combined deletions of two and three subregions was 5.5%, 12.3% and 23.3%, respectively. Heterozygous carriage of severe CFTR mutations was detected in 4.7% patients. The most frequent mutation was F508del (83.3%), followed by CFTRdel21kb (7.1%) and W1282X (4.8%). The frequency of the mild splicing 5T mutation was 5.3%, and its incidence was significantly higher than in the previously published control group (p=0.002). AR genotyping revealed that the most prevailing allele was 21 (CAG) (21.5%). Long alleles with 27 or more CAG-trinucleotides were identified in 7.5% of the tested cases. In addition, 7 CAG heterozygotes with Kleinfelter syndrome were found. CONCLUSION: during primary complex laboratory diagnostics in a heterogeneous group of infertile men, it is advisable to detect AZF deletions and the most frequent CFTR mutations, including F508del, CFTRdel21kb, 1677delTA, 2143delT, W1282X and 5T. The more comprehensive analysis of CFTR mutations is justified only in patients with verified obstructive infertility. Sequencing of panels associated with infertility genes using NGS technology is promising.

Structural Alterations in Human Fibroblast Growth Factor Receptors in Carcinogenesis.

Fibroblast growth factor (FGF) plays an important role in human embryogenesis, angiogenesis, cell proliferation, and differentiation. Carcinogenesis is accompanied by aberrant constitutive activation of FGF receptors (FGFRs) resulting from missense mutation in the FGFR1-4 genes, generation of chimeric oncogenes, FGFR1-4 gene amplification, alternative splicing shift toward formation of mesenchymal FGFR isoforms, and FGFR overexpression. Altogether, these alterations contribute to auto- and paracrine stimulation of cancer cells and neoangiogenesis. Certain missense mutations are found at a high rate in urinary bladder cancer and can be used for non-invasive cancer recurrence diagnostics by analyzing urine cell pellet DNA. Chimeric FGFR1/3 and amplified FGFR1/2 genes can predict cell response to the targeted therapy in various oncological diseases. In recent years, high-throughput sequencing has been used to analyze exomes of virtually all human tumors, which allowed to construct phylogenetic trees of clonal cancer evolution with special emphasis on driver mutations in FGFR1-4 genes. At present, FGFR blockers, such as multi-kinase inhibitors, specific FGFR inhibitors, and FGF ligand traps are being tested in clinical trials. In this review, we discuss current data on the functioning of the FGFR family proteins in both normal and cancer cells, mutations in the FGFR1-4 genes, and mechanisms underlying their oncogenic potential, which might be interesting to a broad range of scientists searching for specific tumor markers and targeted anti-cancer drugs.

[Genetic and biochemical features of the monogenic hereditary urolithiasis]. / Geneticheskie i biokhimicheskie osobennosti nasledstvennykh monogennykh form mochekamennoi bolezni.

Urolithiasis is a common urological problem. In most cases, this multifactorial pathology develops due to the combination of inherited low-penetrance gene variants and environment factors such as urinary tract infections and unbalanced diet. However, some cases are monogenic. These hereditary forms of urolithiasis manifest in childhood, and are characterized by multiple, bilateral and recurrent kidney stones and progress to chronic renal failure relatively early. Due to widening acceptance of exome and gene panel sequencing, substantially larger percentages of urolithiasis cases are now attributed to hereditary causes, up to 20% among patients of 18 years old or younger. Here we review genetic and biochemical mechanisms of urolithiasis, with an emphasis on its hereditary forms, including fermentopathies (primary hyperoxaluria, adenine phosphorobosyltransferase deficiency, phosphoribosyl-pyrophosphate-synthetase deficiency, xanthinuria, Lesch-Nihan syndrome) and these caused by membrane transport alterations (Dent's disease, familial hypomagnesia with hypercalciuria and nephrocalcinosis, hypophosphatemic urolithiasis, distal tubular acidosis, cystinuria, Bartter's syndrome). We suggest a comprehensive gene panel for NGS diagnostics of the hereditary urolithiasis. It is expected that accurate and timely diagnosis of hereditary forms of urolithiasis would enable the counselling of the carriers in affected families, and ensure personalized management of the patients with these conditions.

Specific Localization of Missense Mutations in the VHL Gene in Clear Cell Renal Cell Carcinoma.

Missense mutations in the VHL gene during sporadic clear cell renal cell carcinoma were studied to evaluate their localization in relation to functionally important motifs of the VHL protein. Somatic mutations were identified in 124 of 307 samples. All missense mutations in the α-domain were localized in the binding site for elongin C. Substitutions in the ß-domain (77%) were found in the HIF-binding site. Five missense mutations were absent in these sites, which illustrates their role in VHL protein formation or suppressor function of other protein cofactors. Mutation c.392A→T (p.N131I) was identified for the first time. Our results hold much promise to estimate the boundaries of functionally important sites in the VHL suppressor gene and contribute to the interpretation of a pathogenic role of mutations in direct DNA diagnostics.

[Genetic risk factors for sporadic germ cell testicular tumors].

INTRODUCTION: Approximately 95% of all testicular cancers are testicular germ cell tumors (GCTTs), represented by seminoma and nonseminoma germ cell testicular cancer. There is a hypothesis that the formation of GCTTs begins in early embryogenesis being a part of testicular dysgenesis syndrome (TDS). AIM: To determine the role of genetic factors in the development of GCTTs. MATERIALS AND METHODS: We studied the frequency of alleles and genotypes KITLG (rs995030, rs1508595), SPRY4 (rs4624820, rs6897876) and BAK1 (rs210138) in 97 fertile men (control), and 73 patients with GCTTs (34 seminoma and 39 nonseminoma). RESULTS: GCTTs were statistically significantly associated with KITLG rs1508595 gene (p=0.0003 for allele G, p=0.0014 for genotype GG), and with rs995030 gene (p=0.0031 for genotype GG). When comparing patients with seminoma and control group, statistically significant differences were found for SPRY4 rs4624820 (p=0.0226 for the A and p=0.04 for the AA), for KITLG rs995030 (p=0.0375 for the G and p=0.0282 for GG), rs1508595 (p=0.0306 for G), for BAK1 rs210138 (p=0.0329 for the G and p=0.0219 for the GG). When comparing patients with nonseminoma and fertile men, statistically significant differences were found only for KITLG rs1508595 (p=0.0005 for the G and p=0.0021 for the GG). There was no statistically significant difference between the allele and genotype frequencies of the investigated genes from seminoma and nonseminoma GCTTs patients. However, these groups differed statistically significantly when genotype combinations of the three genes were investigated (p=0,029; OR 3,709 [1.147-11.99]). The combination of genotypes of the three genes was found to increase the risk of GCTTs by 6.5 times (p=0.0005; OR 6.526 [2.078-20.5], and the risk for seminoma was over 12-fold (p<0.0001; OR 12,68 [3,731-43,11]. CONCLUSION: A comprehensive study of genotypes associated with GCTTs in patients with manifested TDS can be used for risk stratification to identify and follow-up high-risk patients, develop approaches to family counseling and treatment, which is the basis for predictive medicine.

[Polymorphisms of KITLG, SPRY4, and BAK1 genes in patients with testicular germ cell tumors and individuals with infertility associated with AZFc deletion of the Y chromosome].

Testicular cancer is the most common form of solid cancer in young men. Testicular cancer is represented by testicular germ cell tumors (TGCTs) derived from embryonic stem cells with different degrees of differentiation in about 95% of cases. The development of these tumors is related to the formation of a pool of male germ cells and gametogenesis. Clinical factors that are predisposed to the development of germ-cell tumors include cryptorchidism and testicular microlithiasis, as well as infertility associated with the gr/gr deletion within the AZFс locus. KITLG, SPRY4, and BAK1 genes affect the development of the testes and gametogenesis; mutations and polymorphisms of these genes lead to a significant increase in the risk of the TGCT development. To determine the relationship between gene polymorphisms and the development of TGCTs, we developed a system for detection and studied the allele and genotype frequencies of the KITLG (rs995030, rs1508595), SPRY4 (rs4624820, rs6897876), and BAK1 (rs210138) genes in fertile men, patients with TGCTs, and patients with infertility that have the AZFс deletion. A significant association of rs995030 of the KITLG gene with the development of TGCTs (p = 0.029 for the allele G, p = 0.0124 for the genotype GG) was revealed. Significant differences in the frequencies of the studied polymorphisms in patients with the AZFc deletion and the control group of fertile men were not found. We showed significant differences in the frequencies for the combination of all high-risk polymorphisms in the control group, patients with the AZFc deletion and patients with TGCTs (p (TGCTs-AZF-control) = 0.0207). A fivefold increase in the frequency of the combination of all genotypes in the TGCT group (p = 0.0116; OR = 5.25 [1.44-19.15]) and 3.7-fold increase was identified in patients with the AZFc deletion (p = 0.045; OR = 3.69 [1.11-12.29]) were revealed. The genotyping of patients with infertility caused by the AZFc deletion can be used to identify individuals with an increased risk of TGCTs.

[The molecular genetic alterations in mucosa of intestines as markers of oncologic progression and estimate of effectiveness of anti-reflux operations in patients with Barrett's esophagus].

The development of disease of Barrett's esophagus is based on processes of metaplasia of epithelium of esophagus when as a result of reflux of gastric juice and bile acids the normal planocellular epithelium of esophagus is replaced by cylindrical epithelium of intestinal type. Thereupon, Barrett's esophagus is progressing up to dysplasia and adenocarcinoma of esophagus. The progression from precancerous states up to tumor is related to development of genome disorders in cells associated with malignant transformation. The genetic and epigenetic alterations conditioning tumor growth can be used as markers of prognosis of clinical course of disease. To receive possible markers of progression of Barrett's esophagus the study was organized concerning methylation of such genes-suppressors of tumor growth as MGMT, CDH1, p16/CDKN2A, DAPK, RAR-ß and RUNX3 in patients with Barrett's esophagus and adenocarcinoma of esophagus. The effectiveness of applied anti-reflux surgical treatment was evaluated too. The abnormal methylation of studied genetic panel in patients with Barrett's esophagus prior to surgical treatment was observed reliably more frequently in altered epithelium as compared with unaltered epithelium (p<0.0001), under dysplasia as compared with metaplasia (p<0.0358) and in the presence of long (>3 cm) segments of altered epithelium as compared with short (<3 cm) segments (p=0.0068). In normal epithelium, prior to operation, abnormal methylation of panel of genes was detected in 7/60 (12%) of patients. Against the background of surgical treatment number of long and short segments of altered epithelium of esophagus reliably decreased (p<0.05). At that, in short segments after operation rate of methylation increased significantly (p=0.0068). Though after operation number of patients with Barrett's esophagus and dysplasia and metaplasia decreased, the rate of abnormal methylation in the other patients increased. It is demonstrated that anti-reflux operation ameliorates condition of mucous membrane of esophagus under Barrett's esophagus. However, in cases without regression significant increasing of rate of abnormal methylation of studied panel of genes is occurred. This is a proof that abnormal methylation of system of genes is related to worse response to application of anti-reflux surgical treatment.

[Point somatic mutations in bladder cancer: key carcinogenesis events, diagnostic markers and therapeutic targets].

Development of bladder cancer (BC) involves accumulating several genetic alterations in somatic cells: point mutations, extended deletions in the localization of tumor suppressor genes, amplification of oncogenes, aberrant DNA methylation, changes in the expression pattern of regulatory RNAs and numerous structural genes. From all of the above, point mutations have the greatest potential as diagnostic markers, as they frequently occur in carcinogenesis, characterize initiation and further clonal evolution of malignancy and represent a change in DNA detectable by routine molecular genetic methods. If we look at the clinical classification of bladder cancer, 90% of the BC presented by urothelial carcinoma, 80% of patients had superficial and 20% - of muscle-invasive tumors. The differences in morphological classification, staging and prognosis of bladder cancer represent different pathogenic pathways of tumor development. Superficial bladder cancer develops through a stage of hyperplasia involving activation of mutations in the genes FGFR3, PIK3CA, HRAS, ERBB2, TERT and others. It is shown that frequent point mutations FGFR3, PIK3CA and TERT are present in the tumor cells in the urine sediment and can be considered as markers for non-invasive molecular genetic diagnosis of primary BC and for monitoring of disease recurrence. Muscle-invasive bladder cancer develops through the stages of dysplasia and carcinoma in situ, in which mutations initially occur in key suppressor genes (TP53 and RB1) and a number of chromatin remodeling genes. This leads to genomic instability and multiple chromosome aberrations that are subjected to selection in the further clonal evolution of tumors towards predominance of more malignant subclones. This review presents systematized information about the main mutations in BC carcinogenesis, their role in the primary tumor progression, metastasizing and role as a target for diagnosis and targeted therapy.

Tumor clonality: research and clinical aspects.

Except for the rare exclusions, all sporadic tumors originate from the only cell. However, the majority of malignant cells proper, constituting the tumor, demonstrate significantly heterogeneous morphology and physiology, differing by mobility, expression profiles, receptor presentation on cell surface, proliferative and angiogenic potential. The data presented in this report confirm the existence of intratumorous clonal heterogeneity. Potential biological and clinical significance of clonal heterogeneity and the existence of genetic differences between the primary tumors and their metastases and the effects of clonal tumor heterogeneity on the metastatic process are discussed.

[Molecular biological characteristics of cancer].

The review presents the main and additional features that distinguish tumor cells from normal tissue cells. They include sustained proliferative signaling, evasion from growth suppressors, resisting cell death, enabling replicative immortality, angiogenesis induction, and invasion and metastasis activation. Basis for the formation of these features is provided by tumor genome instability. Tumors are complex tissues that consist of different cell types interacting with each other as well as with normal cells. An important characteristic of tumor cells is the ability to interact with the tumor microenvironment and the formation of tumor stroma.

[Allelic imbalance of loci 17p13.1 (TP53), 1p36.1 (RUNX3), 16p22 (CDH1) and microsatellite instability in gastric cancer].

We examined allelic imbalance (AI) on loci 17p13.1 (TP53), 1p36.1 (RUNX) and 16p22 (CDHI) and microsatellite instability (MI) with BAT26 in 78 patients with gastric cancer. We have shown a significant difference in the frequency of allelic imbalance of the studied loci among different types of gastric cancer. Frequency of AI in 16p22.1 (CDH1) (p = 0.023), 17p13.1 (TP53) (p = 0.038), microsatellite instability (p = 0.047) and AD two and more loci in a single sample (p = 0.0176) was significantly higher in the intestinal type of gastric cancer than in the diffuse type. We have shown, that, frequency of AI in 16p22.1 (CDH1), and AD two and more loci in a single sample, was higher in thetumors with high or moderate type of tumor cells differentiation (p = 0.0414, p = 0.0057 respectively). We found no significant differences in the groups with metastases in regional lymph nodes, different tumor stage, localization of tumors and the generalization process.

[Structural and functional analysis of tumor genomes and the development of test systems for early diagnosis, prognosis and cancer therapy optimization].

The article discusses results of the structural and functional analysis of molecular genetic abnormalities in various malignant tumors. Investigations have discovered more than 20 new markers for sporadic breast cancer. Several of them formed the test system, allowing the diagnosis with a specificity of 100%. Appearance of TMPRSS2/ERG4 chimeric gene is a frequent tumor-specific event, its expression is correlated with more aggressive forms of prostate cancer, may serve as a molecular marker for tumor cells and androgen assessment of tumor response to hormonal therapy. The effective systems for the early diagnosis of cervix and endometrium cancer were developed as well. Mutations in the VHL, deletions of chromosome 3 and methylation of several genes can predict the course and selection of effective therapy of clear cell kidney cancer, a number of molecular markers were identified for early diagnosis and prognosis of recurrence of bladder cancer. For diagnosis, prognosis and treatment of brain tumors we developed an effective complex system of markers. Protocol of molecular genetics investigation reveals the cause of the disease by more than 90% of patients with retinoblastoma. In order to study abnormal methylation in tumor genomes an innovative technology AFLOAT has been developed that allows to efficiently identify new markers with diagnostic value. Test systems of molecular genetic and epigenetic markers for early diagnosis and prognosis as well as for cancer therapy optimization have shown to be effective, have been approved for use in clinical practice and are being introduced into practical healthcare.

[The systems of molecular genetic markers under cancer of stomach].

The study was organized to investigate the anomalous methylation of genes NA?1, RASSF1A, MLH1, N33, DAPK, the expression of genes hTERT. metalloproteinase MMP7, MMP9, survivin. COX-2, p53. The activity of telomerase in 106 samples of stomach tumors taken through intra-operation way and 53 samples of stomach tumors taken through endoscopic way and 50 samples of biopsy taken from patients with chronic calculous cholecystitis (comparison group) was analyzed too. These changes can be used as additional markers both in diagnostic of cancer of stomach and dynamic monitoring of operated patients.

[Carcinosarcomas of the uterus: molecular-genetic and morphological features].

13 cases of uterine carcinosarcomas have been studied by molecular-genetic method. The impairment of some genes (K-RAS gene in the first exon, TP53 in the 5th-9th exons, PTEN in the 5th and 8th exons) has been found out. The loss of heterozygosity of TP53 gene in epithelium and mesenchyme of the uterus has been detected. According to the estimation of impairment the studied tumors was divided into monoclonal and biclonal ones. This stratification could be use as prognostic criteria of uterine carcinosarcomas clinical presentation.

[Clonal origin of multiple foci of urinary bladder cancer].

To analyze the pattern of molecular damages in urinary bladder cancer (UBC), the authors studied allelic imbalance of chromosome loci 9p21 and 17p13 in 22 patients diagnosed as having multiple primary UBC (2 to 5 foci in each patient). The state of markers has no informative value in 3 (13.6%) cases; in 9 (47.4%) of 19 informative cases, deletion of the same allele was determined in at least one of the loci in question in all tumor nodules, which may point to the monoclonal origin of multiple tumors in these patients. Five (26.3%) of the 19 patients exhibited deletion of the same allele in different tumor nodules, which is suggestive of the active process of clonal evolution and the feasibility of tumor subcloning, which does not preclude the possibility of monoclonal origin. Five (26.3%) of the 19 patients had an imbalance of different alleles in varying nodules, which may show the oligoclonal origin of the tumor nodules concerned. The concordant and discordant patterns of molecular damages are encountered virtually with the same frequency in the tumors of multiple primary UBC, which supports the view that its synchronous tumors can develop both monoclonally through intraluminal dissemination of tumor cells and when there are cancerization fields that determine the occurrence of oligoclonal tumors.

[Some molecular-genetic markers, defining the pathogenesis of superficial and invasive bladder cancer].

We have investigated deletions of 3p14, 9p21, 9q34, 17p13 (TP53) loci, activating FGFR3 mutations in exon 9 and aberrant methylation of RASSF1, RARbeta, P16, P14, CDH1 genes with the aim of the molecular pathogenesis pathways analysis of bladder cancer. FGFR3 activating mutations and 9p21 deletions were observed significantly more frequent in the group of non-invasive bladder cancer pTa than in minimally-invasive cancers pT1 (p = 0.004 and 0.006 respectively). It was shown that groups of superficial and invasive bladder cancer are significantly differing in the frequency of 17p13 (p = 0.006) and 9q34 (p = 0.04) deletions and in aberrant methylation of the gene P16 (p = 0.02). We have revealed some differing molecular-genetic alterations in groups of superficial and invasive bladder cancers. Therefore we suppose that these two types of bladder cancer might have different pathways of development.

[Correlation of p16/INK4a gene damages and protein expression in the tumor tissue of sporadic breast cancer].

A tumor emerges due to the structural and functional abnormalities occurring in the genes, which causes a change in the spectrum of protein molecules. Strong correlations between the gene damages and following changes in the protein spectrum make it possible to study different stages of carcinogenesis and to create a more complete system of molecular markers for the diagnosis of different types of tumors, which comprises protein markers and DNA markers. The present investigation has studied a correlation between the inactivation mechanisms (structural and functional) of the suppressor gene p16/INK4a, which occur at the level of DNA, and the results of its protein expression examined by immunohistochemical methods in the tumor specimens from patients with breast cancer. The investigation could indicate that p16/INK4a gene damage frequently occurred in the tumors of the above type. In the majority of study cases, molecular damages revealed in the gene diminish on its protein expression; however, there are still cases that defy generally accepted explanations.