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Chemotherapy exposure increases leukemia cell stiffness.

ABSTRACT: Deformability of blood cells is known to influence vascular flow and contribute to vascular complications. Medications for hematologic diseases have the potential to modulate these complications if they alter blood cell deformability. Here we report the effect of chemotherapy on leukemia cell mechanical properties. Acute lymphoblastic and acute myeloid leukemia cells were incubated with standard induction chemotherapy, and individual cell stiffness was tracked with atomic force microscopy. When exposed to dexamethasone or daunorubicin, leukemia cell stiffness increased by nearly 2 orders of magnitude, which decreased their passage through microfluidic channels. This stiffness increase occurred before caspase activation and peaked after completion of cell death, and the rate of stiffness increase depended on chemotherapy type. Stiffening with cell death occurred for all cell types investigated and may be due to dynamic changes in the actin cytoskeleton. These observations suggest that chemotherapy itself may increase the risk of vascular complications in acute leukemia.

SUBMITTER: Lam WA

PROVIDER: S-EPMC1852256 | biostudies-literature | 2007 Apr

REPOSITORIES: biostudies-literature

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Chemotherapy exposure increases leukemia cell stiffness.

Lam Wilbur A WA Rosenbluth Michael J MJ Fletcher Daniel A DA

Blood 20061219 8

Deformability of blood cells is known to influence vascular flow and contribute to vascular complications. Medications for hematologic diseases have the potential to modulate these complications if they alter blood cell deformability. Here we report the effect of chemotherapy on leukemia cell mechanical properties. Acute lymphoblastic and acute myeloid leukemia cells were incubated with standard induction chemotherapy, and individual cell stiffness was tracked with atomic force microscopy. When ...[more]

PMID: 17179225

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Project description:BACKGROUND: The molecular changes in vivo in acute myeloid leukemia cells early after start of conventional genotoxic chemotherapy are incompletely understood, and it is not known if early molecular modulations reflect clinical response. METHODS: The gene expression was examined by whole genome 44 k oligo microarrays and 12 k cDNA microarrays in peripheral blood leukocytes collected from seven leukemia patients before treatment, 2-4 h and 18-24 h after start of chemotherapy and validated by real-time quantitative PCR. Statistically significantly upregulated genes were classified using gene ontology (GO) terms. Parallel samples were examined by flow cytometry for apoptosis by annexin V-binding and the expression of selected proteins were confirmed by immunoblotting. RESULTS: Significant differential modulation of 151 genes were found at 4 h after start of induction therapy with cytarabine and anthracycline, including significant overexpression of 31 genes associated with p53 regulation. Within 4 h of chemotherapy the BCL2/BAX and BCL2/PUMA ratio were attenuated in proapoptotic direction. FLT3 mutations indicated that non-responders (5/7 patients, 8 versus 49 months survival) are characterized by a unique gene response profile before and at 4 h. At 18-24 h after chemotherapy, the gene expression of p53 target genes was attenuated, while genes involved in chemoresistance, cytarabine detoxification, chemokine networks and T cell receptor were prominent. No signs of apoptosis were observed in the collected cells, suggesting the treated patients as a physiological source of pre-apoptotic cells. CONCLUSION: Pre-apoptotic gene expression can be monitored within hours after start of chemotherapy in patients with acute myeloid leukemia, and may be useful in future determination of therapy responders. The low number of patients and the heterogeneity of acute myeloid leukemia limited the identification of gene expression predictive of therapy response. Therapy-induced gene expression reflects the complex biological processes involved in clinical cancer cell eradication and should be explored for future enhancement of therapy.

Project description:Membrane ruffling and lamellipodia formation promote the motility of adherent cells in two-dimensional motility assays by mechano-sensing of the microenvironment and initiation of focal adhesions towards their surroundings. Lamellipodium formation is stimulated by small Rho GTPases of the Rac subfamily, since genetic removal of these GTPases abolishes lamellipodium assembly. The relevance of lamellipodial or invadopodial structures for facilitating cellular mechanics and 3D cell motility is still unclear. Here, we hypothesized that Rac1 affects cell mechanics and facilitates 3D invasion. Thus, we explored whether fibroblasts that are genetically deficient for Rac1 (lacking Rac2 and Rac3) harbor altered mechanical properties, such as cellular deformability, intercellular adhesion forces and force exertion, and exhibit alterations in 3D motility. Rac1 knockout and control cells were analyzed for changes in deformability by applying an external force using an optical stretcher. Five Rac1 knockout cell lines were pronouncedly more deformable than Rac1 control cells upon stress application. Using AFM, we found that cell-cell adhesion forces are increased in Rac1 knockout compared to Rac1-expressing fibroblasts. Since mechanical deformability, cell-cell adhesion strength and 3D motility may be functionally connected, we investigated whether increased deformability of Rac1 knockout cells correlates with changes in 3D motility. All five Rac1 knockout clones displayed much lower 3D motility than Rac1-expressing controls. Moreover, force exertion was reduced in Rac1 knockout cells, as assessed by 3D fiber displacement analysis. Interference with cellular stiffness through blocking of actin polymerization by Latrunculin A could not further reduce invasion of Rac1 knockout cells. In contrast, Rac1-expressing controls treated with Latrunculin A were again more deformable and less invasive, suggesting actin polymerization is a major determinant of observed Rac1-dependent effects. Together, we propose that regulation of 3D motility by Rac1 partly involves cellular mechanics such as deformability and exertion of forces.

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Chemotherapy exposure increases leukemia cell stiffness.

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Chemotherapy exposure increases leukemia cell stiffness.

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