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Clonal Evolution in Patients with Chronic Lymphocytic Leukemia

ABSTRACT:

We analyzed clonal evolution in serial samples from five CLL patients who became resistant to the Bruton's tyrosine kinase (BTK) inhibitor ibrutinib, using whole-exome and deep targeted sequencing. We observe a BTK-C481S mutation in one of five patients, and multiple PLCG2 mutations in a second patient. The other patients had an expansion of clones harboring del(8p) carrying additional driver mutations (EP300, MLL2, EIF2A), with one patient developing trans-differentiation into CD19-negative histiocytic sarcoma. We calculated the growth kinetics of ibrutinib-resistant subclones and estimated the size of the resistant clones at treatment initiation, which we validated by droplet-microfluidic technology. Haplo-insufficiency of TRAIL-R, a consequence of del(8p), led to TRAIL insensitivity which may contribute to development of ibrutinib resistance. These findings demonstrate that ibrutinib therapy has the potential to lead to clonal selection and expansion of rare cell populations already present at the time of treatment initiation. They also provide insight into the heterogeneity of genetic changes associated with ibrutinib resistance, previously attributed solely to mutations in BTK and related pathway molecules.

PROVIDER: phs001091 | dbGaP |

SECONDARY ACCESSION(S): PRJNA315752PRJNA315751

REPOSITORIES: dbGaP

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			Action	DRS
	GapExchange_phs001091.v1.p1.xml	Xml
	dbGaPEx2.1.5.xsd	Other
	Study_Report.phs001091.CLL_ClonalEvolution.v1.p1.MULTI.pdf	Pdf
	manifest_phs001091.CLL_ClonalEvolution.v1.p1.c1.GRU.pdf	Pdf
	datadict_v2.xsl	Other

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Project description:The skin epidermis is constantly renewed throughout life. Disruption of the balance between renewal and differentiation can lead to uncontrolled growth and tumor initiation. Basal cell carcinoma (BCC) is the most frequent cancer in human. Cell competition is a biological process that leads to the elimination of cells by winner cells, which have been proposed to be important for tumour initiation. Recent studies identified somatic mutations in cancer drivers in normal tissues that get colonized by clones carrying oncogenic mutations. However, how the different oncogenic mutations impact the balance between renewal and differentiation and lead to clonal expansion, cell competition, tissue colonization and tumor development is currently unknown. Here, using multidisciplinary approaches combining in vivo clonal analysis using intra-vital microscopy, single cell analysis, and functional analysis, we defined at a single cell resolution in living animals how mutations associated with BCC development (SmoM2) affect clonal competition and tumor initiation in real time. We found that SmoM2 expression in the ear epidermis induces a stereotypical pattern of cell competition with clonal expansion leading tumor initiation and invasion. In contrast, SmoM2 expression in the back skin epidermis led to a similar clonal expansion that induces lateral cell competition but without inducing dermal invasion and tumor formation. Single cell analysis showed that oncogene expression is associated with a cellular reprogramming of adult interfollicular cells into embryonic hair follicle progenitor (EHFP) state in the ear but not in the back skin. Comparison between ear and back skin epidermis revealed a very different composition of the dermis with increased stiffness and a denser collagen 1 network in the back skin. Decreasing Collagen 1 expression in the back skin overcame the natural resistance of these cells to undergo EHFP reprogramming and tumor initiation following SmoM2 expression. Altogether our study demonstrates that ECM composition controls the mode of clonal competition and competence to undergo oncogenic transformation upon oncogene expression.

Project description:In this study, we subjected the phenomenon of fractional killing in a clonal population of TRAIL-sensitive cells to careful analysis. We asked whether cells that survive initial exposure to TRAIL are sensitive or resistant to subsequent treatment with TRAIL or other apoptosis-inducing agents. We observed that TRAIL survivor cells were highly resistant to a subsequent treatment with TRAIL 24hr later but that this resistance disappeared following several days in culture. Resistance did not involve downregulation of TRAIL receptors and extended to death ligands that bind different classes of receptors: TRAIL survivors were transiently resistant to FasL and vice versa. Gene expression analysis revealed that NF-kB-mediated inflammatory genes were activated in transiently resistant survivor cells leading to an inflammatory phenotype, but resistance was mediated by an independent mechanism related to changes in signaling at the DISC. Periodic exposure to TRAIL sustained resistance, demonstrating a component of induced survival signaling leading to transient acquired resistance to TRAIL. Based on these results we propose that TRAIL treatment leads to a transient adaptation in survivor cells that can be sustained in cells exposed to long-term TRAIL treatments, leading to acquired resistance. Minimizing the impact of cell-to-cell variability on TRAIL-mediated killing will thus require appropriate spacing of stimuli as well as the use of additional agents that inhibit pro-survival pathways. RNA was collected from Control (untreated) MCF10A cells, Survivors of TRAIL treatment (Day 1), Reset cells (survivors on Day 7), and Repeat cells (Survivors treated with TRAIL on 2 subsequent days). RNA was also collected from Control and Survivor MCF10A cells expressing an IKB-super-repressor construct (Addgene, Plasmid 15291; Boehm et al., 2007), or treated with caspase inhibitors. Three biological experiments were performed (on different days) with 1-2 replicates of each sample collected for each experiment. The total number of samples was 31, on 4 IlluminaRef8 BeadChips (one sample was from an unrelated experiment and was not included). The number of total replicates for each treatment is as follows: Control (7); Survivors (6); Reset (3); Repeat (3); Control-IKB-super-repressor (2); Survivors-IKB-super-repressor (2); Control-zVADinhibitor (2); Survivors-zVADinhibitor (2); Control-IETDinhibitor (2); Survivors-IETDinhibitor (2).

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Clonal Evolution in Patients with Chronic Lymphocytic Leukemia

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