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Although tumor cells are the most reliable source of tumor DNA, biopsy of the tumor is an invasive procedure that should be avoided in some cases. The main limitation of any biopsy is sampling of one tumor site, which may not represent all malignant clones due to the heterogeneity of the tumor. These clones respond to treatment differently and thus directly influence survival of the patient. Circulating cell-free DNA (cfDNA) is released from multiple tumor sites, reflects overall heterogeneity of the tumor, and correlates with its progression. Detection of tumor-specific genetic and epigenetic aberrations in cfDNA could have a direct impact on molecular diagnosis, prognosis, follow-up of disease, monitoring of minimal residual disease, and response to treatment. While most cfDNA data are still experimental, they are very promising. This review focuses on cfDNA in hematological malignancies. K E Y W O R D Sacute lymphoblastic leukemia, acute myeloid leukemia, multiple myeloma, myelodysplastic syndromes | INTRODUCTION AND HISTORYIn recent years, significant advances in diagnosis and treatment of cancer have been made. Nevertheless, invasive and painful procedures, such as tissue or bone marrow (BM) biopsy, are gold standard for disease diagnosis and monitoring. At the same time, they should be avoided in some cases-if BM is fibrotic or tumor tissue is not easily accessible.1 As a single tumor site is sampled during BM biopsy, it may not contain all malignant clones. 2,3 As these clones react to treatment differently, they directly influence survival of patients; thus, easily accessible markers that would mirror the entire heterogeneity of the tumor are sought after. Such putative markers are present in peripheral blood (PB), for example, circulating tumor cells (CTC) or circulating nucleic acids. 3,4 Biopsies of PB-the so-called liquid biopsies-are at the center of attention of researchers as well as clinicians and represent a newer and more comprehensive approach to obtain tumor information. Analysis of circulating molecules (microRNA, cell-free DNA, and others) as well as CTC might describe the tumor in more detail.Cell-free DNA (cfDNA) is one of these possibilities.CfDNA is formed by DNA fragments. These fragments are gathered from all tumor sites into circulation; thus, they mirror the complexity and heterogeneity of the entire tumor. 3 CfDNA may serve as an excellent diagnostic marker as it reflects the disease in more detail than existing biomarkers. Moreover, because of easy access, cfDNA sampling is suitable for repeated analyses. 4 As it correlates with disease progression, it could serve as a prognostic marker as well. 5,6The first reference of cfDNA dates back to 1948. In that year, CfDNA may shortly become such a marker. | CHARACTERISTICS OF CFDNAMolecules of cfDNA are extracellular fragments of short doublestranded DNA found in PB and other body fluids, for example, in urine, saliva, breast milk, and synovial fluid. 16,17 Generally, cfDNA is found in very low concentrations in PB of HD (10-100...

Objectives Progress in multiple myeloma treatment allows patients to achieve deeper responses, for which the assessment of minimal residual disease (MRD) is critical. Typically, bone marrow samples are used for this purpose; however, this approach is site‐limited. Liquid biopsy represents a minimally invasive and more comprehensive technique that is not site‐limited, but equally challenging. Methods While majority of current data comes from short‐term studies, we present a long‐term study on blood‐based MRD monitoring using tumor‐specific cell‐free DNA detection by ASO‐qPCR. One hundred and twelve patients were enrolled into the study, but long‐term sampling and analysis were feasible only in 45 patients. Results We found a significant correlation of quantity of tumor‐specific cell‐free DNA levels with clinically meaningful events [induction therapy (P = .004); ASCT (P = .012)]. Moreover, length of cfDNA fragments is associated with better treatment response of patients. Conclusions These results support the concept of tumor‐specific cell‐free DNA as a prognostic marker.

Congenital heart defects, dysmorphic facial features and intellectual developmental disorders (CHDFIDD) syndrome in humans was recently associated with mutation in CDK13 gene. In order to assess the loss of function of Cdk13 during mouse development, we employed gene trap knock-out (KO) allele in Cdk13 gene. Embryonic lethality of Cdk13-deficient animals was observed by the embryonic day (E) 16.5, while live embryos were observed on E15.5. At this stage, improper development of multiple organs has been documented, partly resembling defects observed in patients with mutated CDK13. In particular, overall developmental delay, incomplete secondary palate formation with variability in severity among Cdk13-deficient animals or complete midline deficiency, kidney failure accompanied by congenital heart defects were detected. Based on further analyses, the lethality at this stage is a result of heart failure most likely due to multiple heart defects followed by insufficient blood circulation resulting in multiple organs dysfunctions. Thus, Cdk13 KO mice might be a very useful model for further studies focused on delineating signaling circuits and molecular mechanisms underlying CHDFIDD caused by mutation in CDK13 gene.

1 Oddělení chemie a toxikologie, Výzkumný ústav veterinárního lékařství, v.v.i., Brno 2 Klinika komplexní onkologické péče, Masarykův onkologický ústav, Brno 3 Oddělení epidemiologie a genetiky nádorů, Masarykův onkologický ústav, Brno SouhrnCyklin-dependentní kinázy (CDKs) se účastní celé řady buněčných procesů a zcela zásadní roli zastávají v regulaci buněčného dělení a transkripce. V nedávné době se podařilo identifi kovat CDK12 jako důležitý faktor v regulaci transkripce genů BRCA1, ATM, ATR, FANCI a FANCD2 zapojených do odpovědi buňky na poškození DNA. Porucha funkce těchto genů vede ke vzniku genomové nestability, což je jeden z klíčových stavů v procesu kancerogeneze. Z uvedeného postavení CDK12 vyplývají i možné klinické konsekvence, které jsou postupně dokazovány. Jedná se především o zjištění, že v řadě nádorů (např. karcinomy vaječníků, prsu, prostaty, tlustého střeva) dochází v důsledku mutace k poškození funkce nebo snížení exprese CDK12, což může zvýšit citlivost nádoru k cytostatikům způsobujícím poškození DNA (např. platinové deriváty, alkylační látky) a k inhibitorům oprav DNA (např. PARP inhibitory). Tato skutečnost již byla potvrzena na modelu serózního ovariálního karcinomu. CDK12 se tak stává potenciálním terapeutickým cílem léčiv, jejichž úkolem je navodit v nádorových buňkách syntetickou letalitu. Náš přehledový článek přináší poslední informace o významu CDK12 v kancerogenezi a o potenciálních možnostech využití CDK12 pro klinickou praxi. Klíčová slovacyklin-dependentní kináza 12 -mutace -opravy DNA -PARP inhibitor -platinová cytostatika SummaryCyclin-dependent kinases (CDKs) participate in many cellular processes and play a crucial role in the regulation of cell cycle and transcription processes. Recently, CDK12 was identifi ed as a key factor orchestrating transcription of genes, such as BRCA1, ATM, ATR, FANCI and FANCD2, which are involved in the DNA-damage response pathway. Importantly, inhibition of function of these genes commonly leads to induction of genomic instability followed by cancer development, but the precise contribution of CDK12 to these processes is to be unveiled. Nevertheless, several mutations aff ecting function of CDK12 were already identifi ed in a variety of tumors of diff erent origin (ovary, breast, prostate, intestine) making tumors sensitive to cytostatics promot ing DNA damage (platin derivatives, alkylating regimens) and inhibitors of DNA repair (PARP inhibitors). Such an eff ect has been already observed in the model of high grade serous ovarian carcinomas. Thus, CDK12 is becoming a potential therapeutic target of drugs causing synthetic lethality in these cells. Our review summarizes most recent information about CDK12 function in cancer and discusses potential use of CDK12 in clinics. Key wordscyclin-dependent kinase 12 -mutation -DNA repair -PARP inhibitor -platin cytostatics Práce byla podpořena grantem IGA MZ ČR č. NT14599-3, rozvojovým projektem organizace MZe č. MZE-00027162/02:2 a prostředky institucionální podpory výzkumné organizace MOÚ poskytnut...