Study On The Relationship Between Whole Y Chromosome Loss In Bone Marrow And Male Hematologic Malignancies

The mechanism of hematologic malignancies is undefined and considered as a interaction result of multiple factors among which gene mutation and chromosome abnormal karyotype are important factors. Most hematologic malignancies are in companywith abnormalities of chromosomes. Therefore chromosome karyotypic analysisprovides many bases for diagnostic classification, treatment, prognosis, follow-up,and pathogenesisexploration of hematological system disorders. As a male-specificacrocentric chromosome, Y chromosome plays a decisive role insexual differentiationand male reproductive functions. A large number of studies have foundthat therelationship between Y chromosome and cancer is also inseparable. At least20kindsof malignant cells have been reported involved with Y chromosome deletions existingindependently or combined with otherchromosome structural abnormalities. Inmalignant hematological diseases, Y chromosome is also one of the chromosomes inwhich deletion most likely happen in chromosomal abnormalities of malignant cells.But loss of Y chromosome may happen gradually with age increasing, so loss of Ychromosome may also occur in bone marrow cells examined normal of the older male.Therefore, in the treatment of old male patients with hematological disorders, thequestion whether loss of Y chromosome, found in their bone marrows, is derived ofphysiological aging loss of normal cells, or a sign of the cloning of malignant cells inthe bone marrow, remains an endless controversy for many years. This study aims toexplore whether the loss of Y chromosome exists independently or co-exists withamplification and deletion of other cancer related genes and its relevance tohematologic malignancies. Objective: To study the relationship between loss of Y chromosome in bonemarrow and hematologic malignancies of the male, i.e. whether loss of Ychromosome is a physiological phenomenondue to the increase in age which is notrelated to the diseases, or it is a chromosome instability factor exists independentlyand results to hematologic malignancies occurance or susceptibility to cancer. And todetermine in the future whether consider loss of Y chromosome tracking as anevaluation indicator to remission or relapse of hematological diseases in its diagnosis,treatment and tracking follow-up.Methods: The samples of this study were bone marrow or leukemia bloodspecimens which were from the male patients of hematological diseases in theAffiliated Hospital of the University of Oklahoma, and sent to the GeneticsLaboratory of Health Science Center. This study applied conventional cytogenetictechniques to filter out specimens with loss of Y chromosome as a sole chromosomeabnormality and no numerical changes or abnormalities of other chromosomes. It alsoapplied comparative genomic hybridization (arrayCGH) to, on the one hand, detectwhether the sample DNA contains gene copy number changes which were difficult todetect using traditional chromosome analysis techniques, so as to identify in thespecimens of hematological diseases whether loss of Y chromosome existedindependently or along with duplication and deletion of important genes in otherchromosomes, and whether the entire Y chromosome was missing or only duplicationand deletion of a small fragment or an important gene; on the other hand, compareincrease or decrease in the proportion of bone marrow germinal cells and45, X,-Y bycomparing the karyotype evolution of the same patient before and after the treatmentso as to identify the relationship between appearance and disappearance ofchromosome karyotype with loss of Y chromosome and the treatment ofhematological diseases.Results:1. Genetics Laboratory of the University of Oklahoma received tissue specimens from1770male patients during2007and March,2014. After karyotype analysis, atotal of108patients were detected with a Y chromosome deletion of abnormalkaryotype, accounting for6%which was close to the reported8%-15%. Among them,86patients were only with only45, X,-Y and no numerical changes or abnormalitiesof other chromosomes. Among them, the median age was72; the youngest was5andthe oldest was88. Another22patients were identified with beside Y chromosomedeletion, complex numerical changes or structural abnormalities of otherchromosomes.2. Fluorescence in situ hybridization (FISH) was applied to detect Y chromosomedeletion proportion of interphase cells of the above86patients because FISH is moreaccurate in detecting the ratio of cells with abnormal karyotype.45, X,-Y cell ratio of37patients was greater than30%. By comparing four diseases with more patientsAML, MDS, NHL and MM, karyotype and FISH show common accuracy, but FISHhas higher sensitivity.3. Comparative genomic hybridization (arrayCGH) showed among37patientswhose45, X,-Y cell ratio was greater than30%,33were detected with only Ychromosome deletions and no abnormal gene copy numbers of important segmentsor genes of other chromosomes. Another two patients were with Y chromosomedeletion of the long arm and the normal existence of the short arm. Only two patientswere with gains and deletions of tumor-related genes in other chromosomes.4. By summarizing the same patients’ multiple chromosome detection andpathological examinations of bone marrow, it was found the cell ratio of Ychromosome deletions may decrease with AML clinical hematological remission andeven disappeared, but reappeared at the time of relapse.Conclusions:1. Loss of Y chromosome in male patients’ bone marrow of hematologicaldiseases is a common abnormal karyotype, and the ratio is about6%-8%.2. Loss of Y chromosome exists independently in hematological diseases, not accompanied by copy of oncogenes and missing of tumor suppressor genes. It is achromosome instability factor exists independently; on the one hand, it mayrepresents a genetic marker of tumor clone; on the other hand, it may be a physiologicloss from normal cells and result a high susceptibility to hematological diseases orsolid tumor.3. In hematological diseases, the long arm deletion in Y chromosome is morecommon than the short arm deletion.4. In detecting abnormal karyotypes, FISH can detect metaphase and interphasecells, analyze a large number of cells, obtain more accurate cell ratio and is notaffected by cell division cycle.5. For AML patients, the cell ratio of Y chromosome deletions may decrease withthe clinical hematological remission and even disappeared, but reappeared at the timeof relapse.Main innovations:1. Applying cytogenetic techniques combined with molecular genetic techniquesto accurately detect karyotype abnormalities in hematological diseases.2. Applying arrayCGH to identify in hematological diseases with Y chromosomedeletions whether there is duplication of oncogenes or deletion of tumor suppressorgenes; whether Y chromosome deletion is a factor that exists independently.3. By integrating changes of karyotype and cell ratio of Y chromosome deletionbefore and after the treatment, it identified a clear relationship betweenY chromosomeand hematological diseases, which makes an important clinical significance toconsider it as a sign of malignant tumor clone for the detection, diagnosis, treatmentand follow-up.