@conference{
author = "Denčić Fekete, Marija and Karan-Đurašević, Teodora and Vuković, Vojin and Jovanović, Jelica and Sanader, Senka and Antić, Darko",
year = "2023",
abstract = "Chronic lymphocyti c leukemia (CLL) is a malignancy of mature CD5+ B lymphocytes that is characterized by excepti onal
clinical and biological heterogeneity. The Rai and Binet staging systems, developed in the late 1970s to early 1980s,
are used in clinical practi ce to strati fy CLL pati ents into risk categories and to help guide clinical follow-up opti ons: to
treat or to watch and wait. However, in early-stage disease, these systems are unable to predict what pati ents will
face the progression to a more aggressive disease. That means, a number of molecular markers with prognosti c and/
or predicti ve impact exist and their assessment is strongly recommended in all pati ents prior to treatment initi ati on.
One of the fi rst recognized prognosti c genomic aberrati ons in CLL include those detected by fl uorescence in situ
hybridizati on (FISH): del(17p), del(11q), trisomy 12 and del(13q), and the immunoglobulin heavy variable (IGHV) gene
somati c hypermutati on (SHM) status. Moreover, the rapid development of genomics techniques greatly expanded
the understanding of CLL at the molecular level in the past decade. This resulted in the discovery of many newer
prognosti c markers based on chromosomal aberrati ons or gene mutati ons. For instance, next-generati on sequencing
(NGS) studies have led to the discovery of recurrently mutated genes in CLL, such as NOTCH1, SF3B1, BIRC3, XPO1,
POT1, NFKBIE and EGR2, that are associated with poor clinical outcome. Among all of these biomarkers, the disti ncti on
between markers of prognosti c and predicti ve values should be made. Prognosti c markers refer to biomarkers that can
provide informati on regarding the pati ent's outcome regardless of treatment. They are o����� en assessed before treatment
to help guide decisions on to treat or not. Markers associated with overall survival (OS) or ti me to fi rst treatment
(TTFT) represent such examples. On the other hand, predicti ve markers are related to therapeuti c interventi ons
with the ability to predict treatment response to a drug. These markers are normally assessed when pati ents receive
the parti cular therapy. Some markers can be both prognosti c and predicti ve. The Nati onal Comprehensive Cancer
Network guideline recommends testi ng of TP53 geneti c alterati ons, IGHV mutati on status, and several well-established
cytogeneti c markers for CLL prognosti cati on. Of these, TP53 mutati ons, IGHV unmutated status, del(17p), and
del(11q), as well as complex karyotype (the presence of three or more unrelated clonal chromosomal abnormaliti es
in a sample), are associated with poor prognosis. Normal karyotype and trisomy 12 are considered as intermediate
prognosti c factors, whereas del(13q) is associated with a favorable prognosis. The higher frequencies of the
previously menti oned unfavorable markers (except for IGHV) found in the treated populati on usually imply the clonal
evoluti on during disease progression or change in clonal dynamics induced by therapies, especially chemotherapies.
Diff erent molecular and genomic techniques are employed for detecti ng molecular biomarkers in CLL. For IGHV
mutati on status, the preferred method is Sanger sequencing to detect mutati ons in genomic DNA or cDNA following
PCR, and align the resulti ng sequences to the germline IGHV using the IMGT/V-QUEST analyti c tool, where ≥ 98%
homology to the germ line is interpreted as unmutated, >2% nonhomology as mutated, and 97.0% to 97.9% is
interpreted as borderline. Prognosti cally signifi cant chromosomal abnormaliti es are frequently detected using
fl uorescence in situ hybridizati on, array comparati ve genomic hybridizati on or conventi onal karyotyping. Fluorescence
in situ hybridizati on, although off ers a high sensiti vity and specifi city, requires prior knowledge of chromosomal
lesions for the probe designs and are limited to the chosen panel genes. The technique has limitati ons in detecti ng
possible complex cytogeneti c abnormaliti es, as well. On the other hand, karyotyping and array comparati ve genomic
hybridizati on provide genome-wide coverage. Despite the fact that array comparati ve genomic hybridizati on does not
eff ecti vely detect balanced chromosomal rearrangements, it uncovers more genomic abnormaliti es than karyotyping
as the probe-based technology examines the chromosomal structure at a much higher resoluti on. Development in
NGS technology in the past two decades, made the technique, especially targeted sequencing of gene panels, much
less costly and accessible. Currently, in Serbia, geneti c techniques such as FISH, conventi onal karyotyping, Sanger
sequencing and NGS are available for detecti on of CLL biomarkers. Advances in the understanding of CLL pathogenesis
have consequently led to the development of several highly eff ecti ve targeted therapies, including Bruton tyrosine
kinase (BTK), phosphati dylinositol 3-kinase, and BCL2 apoptosis regulator (BCL2) directed inhibitors. B-cell survival
and proliferati on is regulated by the BCR signaling pathway. In normal B cells, BCR is triggered by anti gen ligati on,
leading to acti vati on of a cascade of tyrosine kinases, including BTK. BCR signaling is aberrantly acti vated in many B-cell
malignancies, including CLL. Ibruti nib has demonstrated high clinical effi cacy acti ng as an irreversible potent inhibitor of
Bruton's tyrosine kinase and targets several key components of the BCR pathway. However, despite having 80% to 90%
response rate, 10% to 15% of CLL pati ents, who respond initi ally, develop ibruti nib resistance and disease relapse in 2 to
3 years on ibruti nib treatment, mainly because of the acquisiti on of a BTK C481S mutati on. The mutati on prevents the
drug from forming a covalent bond with the C481 residue that weakened the drug-BTK binding by 500-fold. As a result,
BCR signaling and cell proliferati on were restored in the tumor cells. BTK mutati ons may be found in approximately 70%
of CLL pati ents who progressed on ibruti nib treatment. Another resistance mechanism is through acquired acti vati ng
mutati ons in PLCG2, which is found in approximately 10% of the cases. Given these evidences, the current Nati onal
Comprehensive Cancer Network guideline recommends testi ng for BTK and PLCG2 mutati ons for CLL pati ents receiving
ibruti nib who are suspected of having disease progression. NGS has become the opti mal method for detecti ng BTK
or PLCG2 mutati ons in the se����� ng of ibruti nib treatment, as multi ple mutati ons in both genes may occur in the same
specimen. Currently, approximately 20% of CLL pati ents who progressed on ibruti nib do not have either BTK or PLCG2
mutati ons; thus, with NGS, it is possible to uncover other less common but yet undefi ned drug-resistance mutati ons.
In additi on to BTK and PLCG2 mutati ons known to confer ibruti nib resistance, other molecular markers have
been associated with an upfront high risk of relapse on ibruti nib treatment. It has been reported that complex
karyotype, del(17p)/TP53 mutati on, and del(18p) at baseline before ibruti nib treatment are strongly associated
with disease relapse. Other approved targeted agents for CLL treatment include the phosphati dylinositol 3-kinase
inhibitors idelalisib and duvelisib and BCL2 inhibitor venetoclax. For venetoclax, a novel BCL2-G101V mutati on was
identi fi ed to prevent drug acti vity through drug-protein interacti on. Each pati ent with CLL may have several clinical
and molecular markers of confl icti ng prognosti c signifi cance simultaneously, making the precise prognosti cati on
challenging. Today is of the greatest importance to apply ultrasensiti ve techniques to reveal molecular relapses
a����� er therapy initi ati on and to detect minimal residual disease a����� er pati ents achieve complete responses.",
publisher = "Belgrade : Serbian Association on for Cancer Research",
journal = "6th Congress of the Serbian Association for Cancer Research (SDIR)",
title = "Signifi cance of molecular diagnosti cs in therapy of chronic lymphocytic leukemia",
pages = "55-54",
number = "1",
url = "https://hdl.handle.net/21.15107/rcub_imagine_2102"
}
