Stefan Lozenov

Dr. Stefan Lozenov

orcid

Research Focus & Metrics

Academic Career Length

6Years (2021-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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Verified
Journal Article
Open access
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SLStefan Lozenov
Stefan Lozenov
Boris KrastevBoris Krastev
Boris Krastev
GNGeorgi Nikolaev
Georgi Nikolaev
Monika Peshevska-SekulovskaMonika Peshevska-Sekulovska
Monika Peshevska-Sekulovska
MPMilena Peruhova
Milena Peruhova
Tsvetelina VelikovaTsvetelina Velikova
Tsvetelina Velikova
The genetic and metabolomic abundance of the microbiome exemplifies that the microbiome comprises a more extensive set of genes than the entire human genome, which justifies the numerous metabolic and immunological interactions between the gut microbiota, macroorganisms and immune processes. These interactions have local and systemic impacts that can influence the pathological process of carcinogenesis. The latter can be promoted, enhanced or inhibited by the interactions between the microbiota and the host. This review aimed to present evidence that interactions between the host and the gut microbiota might be a significant exogenic factor for cancer predisposition. It is beyond doubt that the cross-talk between microbiota and the host cells in terms of epigenetic modifications can regulate gene expression patterns and influence cell fate in both beneficial and adverse directions for the host’s health. Furthermore, bacterial metabolites could shift pro- and anti-tumor processes in one direction or another. However, the exact mechanisms behind these interactions are elusive and require large-scale omics studies to better understand and possibly discover new therapeutic approaches for cancer.

Verified
Journal Article
Open access
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Tsvetelina VelikovaTsvetelina Velikova
Tsvetelina Velikova
Boris KrastevBoris Krastev
Boris Krastev
SLStefan Lozenov
Stefan Lozenov
RGRadostina Gencheva
Radostina Gencheva
MPMonika Peshevska-Sekulovska
Monika Peshevska-Sekulovska
MPMilena Peruhova
Milena Peruhova
The interplay between drugs and microbiota is critical for successful treatment. An accumulating amount of evidence has identified the significant impact of intestinal microbiota composition on cancer treatment response, particularly immunotherapy. The possible molecular pathways of the interaction between immune checkpoint inhibitors (ICIs) and the microbiome can be used to reverse immunotherapy tolerance in cancer by using various kinds of interventions on the intestinal bacteria. This paper aimed to review the data available on how the antibiotic-related changes in human microbiota during colorectal cancer (CRC) treatment can affect and determine ICI treatment outcomes. We also covered the data that support the potential intimate mechanisms of both local and systemic immune responses induced by changes in the intestinal microbiota. However, further better-powered studies are needed to thoroughly assess the clinical significance of antibiotic-induced alteration of the gut microbiota and its impact on CRC treatment by direct observations of patients receiving antibiotic treatment.

14 June 2025 in Hemato
Verified
Journal Article
Open access
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VSVelizar Shivarov
Velizar Shivarov
SLStefan Lozenov
Stefan Lozenov
Myeloid/lymphoid neoplasms with tyrosine kinase gene fusions (MLN-TK) represent a distinct group of hematologic malignancies recognized in the latest WHO classification due to shared clinical, morphological, and molecular features, and their responsiveness to tyrosine kinase inhibitors (TKIs). Among these, fusions involving the SYK gene, such as ETV6::SYK and ITK::SYK, have emerged as rare but potentially targetable genetic events in both myeloid and lymphoid neoplasms. SYK, a non-receptor tyrosine kinase critical for hematopoietic signalling, can become constitutively activated through gene fusions, driving oncogenesis via the PI3K/AKT, MAPK, and JAK-STAT pathways. ETV6::SYK has been primarily associated with myeloid neoplasms, often presenting with eosinophilia, bone marrow dysplasia, and skin involvement. In vitro and in vivo models confirm its leukemogenic potential and identify SYK as a therapeutic target. Although SYK inhibitors like fostamatinib have shown transient efficacy, resistance mechanisms, possibly involving alternative pathway activation, remain a challenge. The ITK::SYK fusion, on the other hand, has been identified in peripheral T-cell lymphomas, particularly of the follicular helper T-cell subtype, with similar pathway activation and potential for targeted intervention. Additional rare SYK fusions, such as PML::SYK and CTLC::SYK, have been reported in myeloid neoplasms and juvenile xanthogranuloma, respectively, expanding the spectrum of SYK-driven diseases. Accumulating evidence supports the inclusion of SYK fusions in future classification systems and highlights the need for broader molecular screening and clinical evaluation of SYK-targeted therapies.

13 May 2026 in Biomedicines
Verified
Journal Article
Open access
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GNGeorgi Nikolaev
Georgi Nikolaev
SLStefan Lozenov
Stefan Lozenov
MKMarina Konaktchieva
Marina Konaktchieva
BABorislav Emilov Arabadjiev
Borislav Emilov Arabadjiev
IVIvelina Vassileva
Ivelina Vassileva
RKRossitza Ts Konakchieva
Rossitza Ts Konakchieva
Gastrointestinal and liver diseases remain major contributors to global morbidity and mortality, with limited options for curative or regenerative treatment. Innovative cell-based platforms for liver regeneration and treatment include advanced therapy medicinal products (ATMPs) based on mesenchymal stem cells (MSCs), induced pluripotent stem cells (iPSCs), and organoids produced by them, while cell-free systems like extracellular vesicles (EVs) offer a new approach to restore tissue function and homeostasis. This review summarizes key advances from 2020 to 2025 in the translational development of these platforms. MSCs have achieved clinical validation in perianal Crohn’s disease and show encouraging antifibrotic and immunomodulatory effects in cirrhosis and acute-on-chronic liver failure. iPSC and iPSC-derived organoids now enable disease modeling and, in early trials, have shown direct epithelial repair. Emerging cell-free approaches based on EVs promise safer, scalable products. Despite rapid progress, challenges remain in potency standardization, manufacturing, and long-term efficacy assessment. International harmonization through the EMA, FDA, and PMDA frameworks is accelerating the translation of stem cell-based advanced therapy medicinal products. The integration of bioengineering, data science, and ethical governance will determine whether these regenerative approaches evolve into accessible standard-of-care interventions for gastrointestinal and hepatic diseases.

3 September 2024 in Diagnostics
Verified
Journal Article
Open access
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SLStefan Lozenov
Stefan Lozenov
YTYoanna Tsoneva
Yoanna Tsoneva
GNGeorgi Nikolaev
Georgi Nikolaev
RKRossitza Ts Konakchieva
Rossitza Ts Konakchieva
The Ikaros zinc finger factor 1 is a transcription factor with a well-known role in B- and T-cell development. The deletions of IKZF1 have an established significance in acute lymphoblastic leukemia, while reports on its prevalence and prognostic significance among ALL subtypes and regions vary. Breakpoint-specific qPCR is a practical method for testing of the most frequent types of IKZF1 deletions, considering there is clustering of the deletion events. The most commonly reported deletions are Δ4–7, Δ4–8, Δ2–7, and Δ2–8, with deletion Δ4–7 being the most common one. We retrospectively administered a breakpoint-specific qPCR design for screening for the most frequent types of IKZF1 deletions to 78 ALL patients that were diagnosed and treated between 2010 and 2022. We observed the products through gel electrophoresis, and we conducted descriptive statistics, EFS, and OS analyses. Our study found 19 patients with IKZF1 deletions, with two subjects manifesting more than one deletion. The prevalence in the different subgroups was as follows: Ph/+/ B-ALL 46%, Ph/−/ B-ALL 30%, T-ALL/LBL 4%. There was a statistically significant difference in EFS of 39 vs. 0% in favor of patients without deletions (p = 0.000), which translated to a difference in OS of 49 vs. 0% (p = 0.001). This difference was preserved in the subgroup of Ph/−/ B-ALL, while there was no significant difference in the Ph/+/ B-ALL. The most frequently observed type of deletion (15 out of 19) was the Δ4–7. There is a strong negative prognostic impact of the IKZF1 deletions at diagnosis in the observed population. IKZF1 deletion testing through breakpoint-specific qPCR is a practical approach in diagnostic testing for this risk factor. IKZF1 deletions may warrant treatment decisions and intensified treatment strategies to overcome the negative prognostic impact.