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Genetic adaptability of cancer cells under treatment selection pressure in multiple myeloma patients.

ABSTRACT: Purpose Despite advances and significant improvement in survival, multiple myeloma (MM) remains incurable and nearly all patients relapse after treatment. Previous studies have shown a complex spectrum of diverse genetic alterations in almost all patients, but evolution of genomic rearrangements throughout myeloma life cycle has not been investigated. Patients and Methods We performed genomic analysis integrating copy number, allele specific copy number, allele ratio calculations, breakpoint sequencing and rearrangement PCR genotyping on matched diagnosis and relapse samples from 24 MM patients either treated with proteasome inhibitor (bortezomib)-based induction regimen or conventional chemotherapeutic agents. Results All relapse samples have a clear relationship to the diagnosis clone with significant increase of copy number abnormalities (CNAs). Despite a wide diversity of CNAs acquired at relapse, regulators of NF-kB activity were targeted in 25% of the patients. Relapse-associated lesions either appeared as new acquisition or were selected from minor subpopulations at diagnosis. In one third of the patients, we found loss of abnormities containing loss of heterozygosity (LOH) providing evidence that the relapse clone derived from an ancestral clone shared with the dominant diagnosis clone. Remarkably, re-emergence of ancestral clones was almost exclusively found in patients treated with bortezomib, attested to a remarkable adaptability of myeloma cells under targeted drug selection pressure. Conclusion These data suggest that genomic instability and clonal selection are the main forces that drive adaptive changes in MM under drug selection pressure, and they support the proposal to combine several anti-myeloma drugs upfront in order to obtain long-term remissions.

ORGANISM(S): Homo sapiens

PROVIDER: GSE25262 | GEO | 2013/02/13

SECONDARY ACCESSION(S): PRJNA134695

REPOSITORIES: GEO

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Project description:A rare complication of multiple myeloma is a secondary extramedullary involvement, and the skin is one of the possible sites, due to the physiological homing of plasma cells (PCs) into the skin. The article reports a case of a relapsed refractory MM patient, who developed a cutaneous localization after 16 months from the diagnosis under Bortezomib treatment without a leukemic phase. Patient was refractory to Bortezomib. We analyzed the gene expression profiles, the immunophenotypic and immunohistochemistry profiles of MM cells across the course of the disease at the bone marrow and skin localization. Data obtained were further expanded by an immunohistochemistry analysis on selected molecules in a large cohort of MM patients with cutaneous localization. In particular we focused on the expression of chemokines and chemokine receptors involved in the PC skin homing. The mechanisms behind the extramedullary spread and the formation of localizations outside the BM are not completely understood. Several studies investigated the expression profile of myeloma cells in the extramedullary localization by immunohistochemistry without a prospective molecular and immunohistochemistry study across the progression of the disease and consequently the development of extramedullary localization. This case indicates that the skin homing of MM cells could be related to the high CCR10 expression of at the diagnosis and relapse and the loss of CXCR4 surface expression across the progression of the disease in the contest of Bortezomib resistance. This data was further confirmed in a larger series of patients. Moreover, high expression of CD44, together with the down-regulation of CD54 and the lack of expression of CD56 by MM cells in the BM relapse with the re-acquisition of both antigens during the cutaneous relapse may be the mechanism that drives the escape from BM of PCs and their localization into the skin. Our data have identified a possible mechanism that drives the escape from BM of myeloma cells and their localization into the skin.

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Genetic adaptability of cancer cells under treatment selection pressure in multiple myeloma patients.

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