Current knowledge about FLT3 gene mutations, exploring the isoforms, and protein importance in AML.

Acute myeloid leukaemia (AML) is a complex haematological malignancy characterised by diverse genetic alterations leading to abnormal proliferation of myeloid precursor cells. One of the most significant genetic alterations in AML involves mutations in the FLT3 gene, which plays a critical role in haematopoiesis and haematopoietic homeostasis. This review explores the current understanding of FLT3 gene mutations and isoforms and the importance of the FLT3 protein in AML. FLT3 mutations, including internal tandem duplications (FLT3-ITD) and point mutations in the tyrosine kinase domain (FLT3-TKD), occur in 25-30% in AML and are associated with poor prognosis. FLT3-ITD mutations lead to constitutive activation of the FLT3 signalling pathway, promoting cell survival and proliferation. FLT3-TKD mutations affect the tyrosine kinase domain and affect AML prognosis in various ways. Furthermore, FLT3 isoforms, including shorter variants, contribute to the complexity of FLT3 biology. Additionally, nonpathological polymorphisms in FLT3 are being explored for their potential impact on AML prognosis and treatment response. This review also discusses the development of molecular treatments targeting FLT3, including first-generation and next-generation tyrosine kinase inhibitors, highlighting the challenges of resistance that often arise during therapy. The final chapter describes FLT3 protein domain rearrangements and their relevance to AML pathogenesis.

Circulating Tumor Cell Kinetics and Morphology from the Liquid Biopsy Predict Disease Progression in Patients with Metastatic Colorectal Cancer Following Resection.

The liquid biopsy has the potential to improve current clinical practice in oncology by providing real-time personalized information about a patient's disease status and response to treatment. In this study, we evaluated 161 peripheral blood (PB) samples that were collected around surgical resection from 47 metastatic colorectal cancer (mCRC) patients using the High-Definition Single Cell Assay (HDSCA) workflow. In conjunction with the standard circulating tumor cell (CTC) enumeration, cellular morphology and kinetics between time-points of collection were considered in the survival analysis. CTCs, CTC-Apoptotic, and CTC clusters were found to indicate poor survival with an increase in cell count from pre-resection to post-resection. This study demonstrates that CTC subcategorization based on morphological differences leads to nuanced results between the subtypes, emphasizing the heterogeneity within the CTC classification. Furthermore, we show that factoring in the time-point of each blood collection is critical, both for its static enumeration and for the change in cell populations between draws. By integrating morphology and time-based analysis alongside standard CTC enumeration, liquid biopsy platforms can provide greater insight into the pathophysiology of mCRC by highlighting the complexity of the disease across a patient's treatment.

Role of Polymorphisms of NKG2D Receptor and Its Ligands in Acute Myeloid Leukemia and Human Stem Cell Transplantation.

Natural killer cells possess key regulatory function in various malignant diseases, including acute myeloid leukemia. NK cell activity is driven by signals received through ligands binding activating or inhibitory receptors. Their activity towards elimination of transformed or virally infected cells can be mediated through MICA, MICB and ULBP ligands binding the activating receptor NKG2D. Given the efficiency of NK cells, potential target cells developed multiple protecting mechanisms to overcome NK cells killing on various levels of biogenesis of NKG2D ligands. Targeted cells can degrade ligand transcripts via microRNAs or modify them at protein level to prevent their presence at cell surface via shedding, with added benefit of shed ligands to desensitize NKG2D receptor and avert the threat of destruction via NK cells. NK cells and their activity are also indispensable during hematopoietic stem cell transplantation, crucial treatment option for patients with malignant disease, including acute myeloid leukemia. Function of both NKG2D and its ligands is strongly affected by polymorphisms and particular allelic variants, as different alleles can play variable roles in ligand-receptor interaction, influencing NK cell function and HSCT outcome differently. For example, role of amino acid exchange at position 129 in MICA or at position 98 in MICB, as well as the role of other polymorphisms leading to different shedding of ligands, was described. Finally, match or mismatch between patient and donor in NKG2D ligands affect HSCT outcome. Having the information beyond standard HLA typing prior HSCT could be instrumental to find the best donor for the patient and to optimize effects of treatment by more precise patient-donor match. Here, we review recent research on the NKG2D/NKG2D ligand biology, their regulation, description of their polymorphisms across the populations of patients with AML and the influence of particular polymorphisms on HSCT outcome.

Altered Expression of MBNL Family of Alternative Splicing Factors in Colorectal Cancer.

BACKGROUND/AIM: Colorectal cancer is currently the third leading cause of cancer-related deaths and recently, alternative splicing has risen as its important regulator and potential treatment target. In the present study, we analyzed gene expression of the MBNL family of regulators of alternative splicing in various stages of colorectal cancer development, together with the MBNL-target splicing events in FOXP1 and EPB41L3 genes and tumor-related CD44 variants. MATERIALS AND METHODS: Samples of tumor tissue and non-malignant mucosa from 108 patients were collected. After RNA isolation and reverse transcription, the relative gene expression of a selected gene panel was tested by quantitative real-time PCR, followed by statistical analysis. RESULTS: MBNL expression was decreased in tumor tissue compared to non-tumor mucosa. In addition, lower expression was observed for the variants of FOXP1 and EPB41L3, while higher expression in tumor tissue was detected both for total CD44 and its cancer-related variants 3 and 6. Transcript levels of the MBNL genes were not found to be related to any of the studied clinicopathological characteristics. Multiple significant associations were identified in the target gene panel, including higher transcript levels of FOXP1 and CD44v3 in patients with distant metastases and connections between recurrence-free survival and altered levels of FOXP1 and CD44v3. CONCLUSION: Our results identified for the first-time deregulation of MBNL genes in colorectal cancer. Down-regulation of their transcripts in tumor tissue compared to matched non-tumor mucosa can lead to transition of alternative splicing patterns towards a less differentiated phenotype, which highlights the importance of alternative splicing regulation for tumor growth and propagation.

Dynamic Changes of Inhibitory Killer-Immunoglobulin-Like Receptors on NK Cells after Allogeneic Hematopoietic Stem Cell Transplantation: An Initial Study.

Killer-immunoglobulin-like receptors (KIRs) are critical natural killer (NK) cell regulators. The expression of KIRs is a dynamic process influenced by many factors. Their ligands-HLA(Human Leukocyte Antigen) class I molecules-are expressed on all nucleated cells that keep NK cells under control. In hematopoietic stem cell transplantation (HSCT), NK cells play an essential role in relapse protection. In the presented pilot study, we characterized the dynamic expression of inhibitory KIRS (iKIRs), which protect cells against untoward lysis, in donors and patients during the first three months after HSCT using flow cytometry. The expression of all iKIRs was highly variable and sometimes correlated with patients' clinical presentation and therapy regiment. Cyclophosphamide (Cy) in the graft-versus-host disease (GvHD) prevention protocol downregulated KIR2DL1 to just 25% of the original donor value, and the FEAM (Fludarabine + Etoposid + Ara-C + Melphalan) conditioning protocol reduced KIR2DL3. In lymphoid neoplasms, there was a slightly increased KIR2DL3 expression compared to myeloid malignancies. Additionally, we showed that the ex vivo activation of NK cells did not alter the level of iKIRs. Our study shows the influence of pre- and post-transplantation protocols on iKIR expression on the surface of NK cells and the importance of monitoring their cell surface.

Association of miR-125b, miR-17 and let-7c Dysregulations With Response to Anti-epidermal Growth Factor Receptor Monoclonal Antibodies in Patients With Metastatic Colorectal Cancer.

BACKGROUND/AIM: MicroRNAs (miRs) play an important role in the regulation of cancer-related processes and are promising candidates for cancer biomarkers. The aim of the study was to evaluate the association of response to anti-EGFR monoclonal antibodies (mAbs) with selected miR expression profiles, including miR-125b, let-7c, miR-99a, miR-17, miR-143 and miR-145 in metastatic colorectal cancer (mCRC) patients. PATIENTS AND METHODS: This retrospective study included 46 patients with mCRC harbouring wild-type RAS gene treated with cetuximab or panitumumab combined with chemotherapy in first- or second-line therapy. The miR expression was assessed using qRT-PCR. RESULTS: Down-regulation of miR-125b and let-7c and up-regulation of miR-17 were found in the tumour tissue (p=0.0226, p=0.0040, p<0.0001). Objective response rate (ORR) was associated with up-regulation of miR-125b (p=0.0005). Disease control rate (DCR) was associated with up-regulation of miR-125b and let-7c (p=0.0383 and p=0.0255) and down-regulation of miR-17 (p=0.0464). MiR-125b showed correlation with progression-free and overall survival (p=0.055 and p=0.006). CONCLUSION: The results show that up-regulation of miR-125b is associated with higher ORR and DCR and longer survival; let-7c up-regulation and miR-17 down-regulation are associated with higher DCR in mCRC patients treated with anti-EGFR mAbs.

Sonic Hedgehog and Triiodothyronine Pathway Interact in Mouse Embryonic Neural Stem Cells.

Neural stem cells are fundamental to development of the central nervous system (CNS)-as well as its plasticity and regeneration-and represent a potential tool for neuro transplantation therapy and research. This study is focused on examination of the proliferation dynamic and fate of embryonic neural stem cells (eNSCs) under differentiating conditions. In this work, we analyzed eNSCs differentiating alone and in the presence of sonic hedgehog (SHH) or triiodothyronine (T3) which play an important role in the development of the CNS. We found that inhibition of the SHH pathway and activation of the T3 pathway increased cellular health and survival of differentiating eNSCs. In addition, T3 was able to increase the expression of the gene for the receptor smoothened (Smo), which is part of the SHH signaling cascade, while SHH increased the expression of the T3 receptor beta gene (Thrb). This might be the reason why the combination of SHH and T3 increased the expression of the thyroxine 5-deiodinase type III gene (Dio3), which inhibits T3 activity, which in turn affects cellular health and proliferation activity of eNSCs.

Liquid Biopsy in Colorectal Carcinoma: Clinical Applications and Challenges.

Colorectal carcinoma (CRC) is characterized by wide intratumor heterogeneity with general genomic instability and there is a need for improved diagnostic, prognostic, and therapeutic tools. The liquid biopsy provides a noninvasive route of sample collection for analysis of circulating tumor cells (CTCs) and genomic material, including cell-free DNA (cfDNA), as a complementary biopsy to the solid tumor tissue. The solid biopsy is critical for molecular characterization and diagnosis at the time of collection. The liquid biopsy has the advantage of longitudinal molecular characterization of the disease, which is crucial for precision medicine and patient-oriented treatment. In this review, we provide an overview of CRC and the different methodologies for the detection of CTCs and cfDNA, followed by a discussion on the potential clinical utility of the liquid biopsy in CRC patient care, and lastly, current challenges in the field.

Expression of Serpin B9 as a Prognostic Factor of Colorectal Cancer.

BACKGROUND/AIM: Treatment of colorectal cancer (CRC) does not reflect immune interactions between tumours and macro-organisms. Serpin B9 is known as an inhibitor of Granzyme B. The aim of this study was to evaluate the impact of the expression of Serpin B9 in CRC and healthy colon tissue on prognosis. PATIENTS AND METHODS: This retrospective study included 74 CRC patients in all stages. Analysis of gene expression was performed with quantitative polymerase chain reaction with reverse transcription using specific primers and master mix Xceed qPCR SG. Expression was normalized to the reference genes GAPDH, ACTB, and PSMC. RESULTS: Increased expression of Serpin B9 in healthy tissue was significantly associated with longer overall survival (OS). This association was found both in all patients and in the group of patients with distant metastases. CONCLUSION: The presented results support previous evidence of positive influence of the interaction between immune system and tumour on the prognosis of CRC.

Single-Cell Analysis of Circulating Tumor Cells.

Circulating tumor cells (CTCs) are rare cells that can be found in the peripheral blood of cancer patients. They have been demonstrated to be useful prognostic markers in many cancer types. Within the last decade various methods have been developed to detect rare cells within a liquid biopsy from a cancer patient. These methods have revealed the phenotypic diversity of CTCs and how they can represent the complement of cells that are found in a tumor. Single-cell proteogenomics has emerged as an all-encompassing next-generation technological approach for CTC research. This allows for the deconstruction of cellular heterogeneity, dynamics of metastatic initiation and progression, and response or resistance to therapeutics in the clinical settings. We take advantage of this opportunity to investigate CTC heterogeneity and understand their full potential in precision medicine.The high-definition single-cell analysis (HD-SCA) workflow combines detection of the entire population of CTCs and rare cancer related cells with single-cell genomic analysis and may therefore provide insight into their subpopulations based on molecular as well as morphological data. In this chapter we describe in detail the protocols from isolation of a candidate cell from a microscopy slide, through whole-genome amplification and library preparation, to CNV analysis of identified cells from the HD-SCA workflow. This process may also be applicable to any platform starting with a standard microscopy slide or isolated cell of interest.

Prodrug suicide gene therapy for cancer targeted intracellular by mesenchymal stem cell exosomes.

The natural behavior of mesenchymal stem cells (MSCs) and their exosomes in targeting tumors is a promising approach for curative therapy. Human tumor tropic mesenchymal stem cells (MSCs) isolated from various tissues and MSCs engineered to express the yeast cytosine deaminase::uracil phosphoribosyl transferase suicide fusion gene (yCD::UPRT-MSCs) released exosomes in conditional medium (CM). Exosomes from all tissue specific yCD::UPRT-MSCs contained mRNA of the suicide gene in the exosome's cargo. When the CM was applied to tumor cells, the exosomes were internalized by recipient tumor cells and in the presence of the prodrug 5-fluorocytosine (5-FC) effectively triggered dose-dependent tumor cell death by endocytosed exosomes via an intracellular conversion of the prodrug 5-FC to 5-fluorouracil. Exosomes were found to be responsible for the tumor inhibitory activity. The presence of microRNAs in exosomes produced from naive MSCs and from suicide gene transduced MSCs did not differ significantly. MicroRNAs from yCD::UPRT-MSCs were not associated with therapeutic effect. MSC suicide gene exosomes represent a new class of tumor cell targeting drug acting intracellular with curative potential.

lncRNAs in Non-Malignant Tissue Have Prognostic Value in Colorectal Cancer.

Although colorectal cancer (CRC) is the third most frequent cause of cancer related death in Europe, clinically relevant biomarkers for therapy guidance and prognosis are insufficiently reliable. Long non-coding RNAs (lncRNAs) are RNAs over 200 nucleotides long that are not translated into proteins but can influence biological processes. There is emerging evidence for their involvement in solid cancer as oncogenes, tumour suppressors or regulators of cell proliferation and metastasis development. The goal of this study was to evaluate the prognostic effect of selected lncRNAs in a retrospective study on CRC patients from the Czech Republic. We used a quantitative PCR approach to measure the expression in paired non-malignant and tumour tissue samples of CRC patients of nine lncRNAs previously shown to be involved in cancer progression-ANRIL, CCAT1, GAS5, linc-ROR, MALAT1, MIR155HG, PCAT1, SPRY4-IT1 and TUG1. Associations between expression and expression ratios and clinical characteristics and survival were assessed by using univariable Cox proportional hazards models, Kaplan-Meier estimations with the Gehan-Wilcoxon test, the Mann-Whitney U test, the Kruskal-Wallis test and Spearman's correlations. A comparison of expression in tumour tissue (TT) and non-malignant mucosa tissue (MT) showed significant upregulation of CCAT1 and linc-ROR in TT (p < 0.001 and p = 0.001, respectively) and downregulation of ANRIL, MIR155HG and MALAT1 (p = 0.001, p = 0.010, p = 0.001, respectively). Linc-ROR was significantly associated with the presence of synchronous metastases (p = 0.033). For individual tissue types, lower MIR155HG expression in TT was correlated with both shorter overall survival (p = 0.008) and shorter disease-free survival (p = 0.040). In MT, expression ratios of CCAT1/ANRIL and CCAT1/MIR155HG were associated with overall survival (p = 0.005 and p = 0.006, respectively). Our results revealed that changes in expression of lncRNAs between MT and TT hold potential to be used as prognostic biomarkers in CRC patients. Moreover, the ratios of CCAT1 to ANRIL and MIR155HG in MT also exhibit potential for prognosis assessment without tumour sampling. Our results also indicate that cancer progression is associated with detrimental system-wide changes in patient tissue, which might govern patient survival even after successful elimination of tumour or cancerous cells.

IDH1 mutation is associated with lower expression of VEGF but not microvessel formation in glioblastoma multiforme.

INTRODUCTION: Glioblastoma multiforme (GBM) represents the most malignant primary brain tumor characterized by pathological vascularization. Mutations in isocitrate dehydrogenases 1 and 2 (IDH1 and IDH2) were observed in GBM. We aimed to assess the intra-tumor hypoxia, angiogenesis and microvessel formation in GBM and to find their associations with IDH1 mutation status and patients prognosis. METHODS: 52 patients with a diagnosis of GBM were included into the study. IDH1 R132H mutation was assessed by RT-PCR from FFPE tumor samples obtained during surgery. The expression of markers of hypoxia (HIF2α), angiogenesis (VEGF), tumor microvascularity (CD31, CD34, vWF, CD105), and proliferation (Ki-67) were assessed immunohistochemically (IHC). IDH1 mutation and IHC markers were correlated with the patient survival. RESULTS: 20 from 52 GBM tumor samples comprised IDH1 R132H mutation (38.5%). The majority of mutated tumors were classified as secondary glioblastomas (89.9%). Patients with IDH1 mutated tumors experienced better progression-free survival (P = 0.037) as well as overall survival (P = 0.035) compared with wild type tumors. The significantly lower expression of VEGF was observed in GBM with IDH1 mutation than in wild type tumors (P = 0.01). No such association was found for microvascular markers. The increased expression of newly-formed microvessels (ratio CD105/CD31) in tumor samples was associated with worse patient's progression-free survival (P = 0.026). SUMMARY: No increase in HIF/VEGF-mediated angiogenesis was observed in IDH1-mutated GBM compared with IDH1 wild type tumors. The histological assessment of the portion of newly-formed microvessels in tumor tissue can be used for the prediction of GBM patient's prognosis.

The association of miR-126-3p, miR-126-5p and miR-664-3p expression profiles with outcomes of patients with metastatic colorectal cancer treated with bevacizumab.

MicroRNAs regulate the expression of genes involved in several important cancer-related processes including cell adhesion, proliferation, and tumour angiogenesis. Bevacizumab is routinely used in the treatment of patients with metastatic colorectal cancer, but, so far, no reliable biomarker predicting response to bevacizumab has been established. The aim of our retrospective study was to evaluate the association of miR-126-3p, miR-126-5p and miR-664-3p tumour expression levels with outcomes of patients with metastatic colorectal cancer treated with bevacizumab. The study included 63 patients. For the assessment of microRNA expression, gene-specific TaqMan assays were used. The median progression-free survival and overall survival for patients with low tumour expression of miR-126-3p were 8.8 and 20.6 months versus 13.5 months and median overall survival was not reached for patients with high expression ( p = 0.0064 and p = 0.0027), respectively. The median progression-free survival and overall survival for patients with low tumour expression of miR-126-5p were 9.0 and 22.2 months versus 12.0 and 23.4 months for patients with high expression ( p = 0.2113 and 0.6858), respectively. The median progression-free survival and overall survival for patients with low tumour expression of miR-664-3p were 9.1 and 22.5 months versus 8.8 and 23.4 months for patients with high expression ( p = 0.2542 and p = 0.1922), respectively. The multivariable Cox proportional hazards model revealed that miR-126-3p expression was significantly associated with progression-free survival (hazard ratio = 0.28, p = 0.0053) and also with overall survival (hazard ratio = 0.18, p = 0.0046). In conclusion, the results of this study suggest that the expression of miR-126-3p in the tumour tissue was associated with outcome of metastatic colorectal cancer patients treated with bevacizumab.

Post-treatment recovery of suboptimal DNA repair capacity and gene expression levels in colorectal cancer patients.

DNA repair in blood cells was observed to be suboptimal in cancer patients at diagnosis, including colorectal cancer (CRC). To explore the causality of this phenomenon, we studied the dynamics of DNA repair from diagnosis to 1 yr follow-up, and with respect to CRC treatment. Systemic CRC therapy is targeted to DNA damage induction and DNA repair is thus of interest. CRC patients were blood-sampled three times in 6-mo intervals, starting at the diagnosis, and compared to healthy controls. DNA repair was characterized by mRNA levels of 40 repair genes, by capacity of nucleotide excision repair (NER), and by levels of DNA strand breaks (SBs). NER and base excision repair genes were significantly under-expressed (P < 0.016) in patients at diagnosis compared to controls, in accordance with reduced NER function (P = 0.008) and increased SBs (P = 0.015). Six months later, there was an increase of NER capacity, but not of gene expression levels, in treated patients only. A year from diagnosis, gene expression profiles and NER capacity were significantly modified in all patients and were no longer different from those measured in controls. All patients were free of relapse at the last sampling, so we were unable to clarify the impact of DNA repair parameters on treatment response. However, we identified a panel of blood DNA repair-related markers discerning acute stage of the disease from the remission period. In conclusion, our results support a model in which DNA repair is altered as a result of cancer.

Immunohistochemical detection of cancer stem cell related markers CD44 and CD133 in metastatic colorectal cancer patients.

AIM: The goal of this study was to semiquantitatively detect presence of cancer stem cells markers CD44 and CD133 in immunohistochemically stained paired samples of colorectal cancer (CRC) and colorectal liver metastases (CLM). Level of staining intensity was compared to clinical and pathological characteristics of tumors with the aim to identify impact of CD44 or CD133 expression on tumor behavior. PATIENTS AND METHODS: Formalin fixed paraffin embedded samples from 94 patients with colorectal tumor and liver metastases were collected at Sikl's Department of Pathology. Samples were stained by antibodies against CD44 and CD133. Presence and intensity of staining was assessed semiquantitatively by three trained researchers. RESULTS: Patients with higher level of CD133 staining in CRC had longer disease free interval (Cox-Mantel P = 0.0244), whereas we found no relation between CD44 expression and overall survival or disease free interval. CD133 expression in CRC and CLM differed based on CRC grading; in case of CD44 we found differences in staining intensity in individual stages of tumor lymph node invasion. CONCLUSION: Effect of cancer stem cell markers on prognosis of colorectal cancer can vary depending on pathological classification of tumor, and we have shown that CD133, generally considered to be a negative marker, can bear also clinically positive prognostic information in group of patients with colorectal liver metastases.

Differential expression and prognostic role of selected genes in colorectal cancer patients.

AIM: Colorectal cancer (CRC) is one of the most common malignant diseases. The aim of our study was to describe the expression status of 12 selected candidate genes, by comparing paired samples of healthy colon mucosa and tumour tissues and to correlate obtained data with clinical and pathological features, with the goal of revealing associations for individual gene expressions and tumour behaviour. MATERIALS AND METHODS: Samples from 53 patients with CRC were analyzed. Patients were divided into two groups based on the presence or absence of distant metastases at the time of primary tumour surgery. Expression levels were assessed by quantitative real-time polymerase chain reaction. RESULTS: We found changes in the expression of 10 out of 12 analyzed genes. Four genes were significantly up-regulated in tumour tissues: leucine-rich repeat-containing G protein-coupled receptor 5 (LGR5; p<0.001), collagen triple helix repeat containing 1 (CTHRC1; p<0.001), visinin-like 1 (VSNL1; p<0.001) and versican (VCAN; p=0.001). Six genes were down-regulated: destrin (DSTN; p=0.004), mesoderm induction early response 1, family member 3 (MIER3; p<0.001), acyl-CoA synthetase long-chain family member 5 (ACSL5; p=0.002), mitogen-activated protein kinase 1/ERK (MAPK1; p<0.001), claudin 23 (CLDN23; p<0.001) and solute carrier family 26 (sulfate transporter), member 2 (SLC26A2; p<0.001). We recorded longer overall survival (OS) in the group of patients with higher expression of VSNL1 (p=0.032). Patients with more pronounced down-regulation of CLDN23 had shorter OS (p=0.045). In the group of patients without distant metastases, longer OS and disease-free interval (DFI) were found for patients with higher SLC26A2 expression in tumour tissues (p=0.036 and p=0.011, respectively). In the same group, lower expression of VSNL1 in healthy tissue corresponded to a longer DFI (p=0.020), smaller decrease of SLC26A2 and ACSL5 meant longer DFI (p=0.041 and p=0.040, respectively), as did greater increase of LGR5 expression (p=0.026). CONCLUSION: We identified differences in the expression of 10 genes in colorectal cancer tissue compared to healthy colon mucosa, and found prognostic significance for these changes which could be used for the development of a disease risk scoring system.

Infiltration of colorectal carcinoma by S100+ dendritic cells and CD57+ lymphocytes as independent prognostic factors after radical surgical treatment.

BACKGROUND: S100(+) dendritic cells and CD57(+) lymphocytes are factors reflecting the immune system's ability to suppress the progress of tumor growth. CD57(+) cells include natural killer cells and late stages of T-effector lymphocytes. We evaluated the relationship between the known clinical and histological factors and tumor markers as well as the presence of S100(+) and CD57(+) cells in the tissue of colorectal carcinoma with the aim of detecting patients at high risk of short overall survival (OS) or short disease-free interval (DFI) after radical surgical treatment and we further analyzed whether S100(+) and CD57(+) positivity could bring on new information regarding the treatment regimen. MATERIALS AND METHODS: Data of 150 patients (97 males and 53 females) that underwent an elective radical surgical procedure for colorectal cancer were studied. The influence on DFI and on OS of the following parameters was evaluated: grading, staging and positivity for S100 and CD57 by immunohistochemical staining. We also analyzed the relation of preoperative serum levels of the tumor markers Carcinoembryonic Antigen (CEA), Cancer Antigen 19-9 (CA19-9), Cancer Antigen 72-4 (CA72-4), Thymidine kinase (TK), Tissue-Specific Polypeptide Antigen (TPS) and Tissue Polypeptide Antigen (TPA) in relation to S100 and CD57 positivity/negativity for the same patients. RESULTS: OS at 1, 3 and 5 years was 92.2%, 76.5% and 70.2%; the DFI at 1, 3 and 5 years was 85.3%, 64.3% and 49.4%. CD57 positivity in the tumor mass was proven as a positive prognostic factor for OS. Risk of short OS was 2.5-fold higher in patients with low tumor infiltration by CD57(+) lymphocytes. The combination of N2 stage for lymph nodes and the absence of CD57(+) cells was proven to be the strongest negative prognostic factor for OS. No significant influence of CD57 positivity on DFI appeared. There was no significant influence of S100 positivity on OS or DFI; nor was there any statistical dependence of CD57 and S100 positivity or negativity on preoperative serum levels of CEA, CA19-9, CA72-4, TK, TPS or TPA. Both studied factors were shown to be statistically independent factors. CONCLUSION: The present study showed infiltration of colorectal cancer tissue by CD57(+) cells as being an important independent positive prognostic factor for OS.