Thalidomide induces apoptosis in undifferentiated human induced pluripotent stem cells

Thalidomide affects limb formation and multiple myeloma related genes in human induced pluripotent stem cells and their mesoderm differentiation

Although thalidomide is highly teratogenic, it has been prescribed for treating multiple myeloma and Hansen's disease. However, its mechanism of action is not fully understood. Here, we employed a reverse transcription quantitative PCR array to measure the expression of 84 genes in human induced pluripotent stem cells (hiPSCs) and their mesodermal differentiation. Thalidomide altered the expression of undifferentiated marker genes in both cell types. Thalidomide affected more genes in the mesoderm than in the hiPSCs. Ectoderm genes were upregulated but mesendoderm genes were downregulated by thalidomide during mesoderm induction, suggesting that thalidomide altered mesoderm differentiation. We found that FABP7 (fatty acid binding protein 7) was dramatically downregulated in the hiPSCs. FABP is related to retinoic acid, which is important signaling for limb formation. Moreover, thalidomide altered the expression of the genes involved in TGF-β signaling, limb formation, and multiple myeloma, which are related to thalidomide-induced malformations and medication. In summary, iPSCs can serve as useful tools to elucidate the mechanisms underlying thalidomide malformations in vitro.

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Thalidomide downregulated FABP7, a fatty acid binding protein (FABP) cording gene.

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FABP is related to retinoic acid, which is important signaling for limb formation.

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Thalidomide treatment affected the expression of limb formation related genes.

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Thalidomide treatment affected 5 genes related to multiple myeloma.

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Thalidomide upregulated ectoderm but downregulated mesendoderm markers in mesoderm.

VTD in comparison with VCD does not affect stem cell yields with G-CSF only mobilization

Triplet induction regimens are standard of care for newly diagnosed transplant eligible multiple myeloma patients. The combinations of bortezomib and dexamethasone with either cyclophosphamide (VCD) or thalidomide (VTD) are widely used. There are no data available on the impact of the two regimens on stem cell harvest by using G-CSF only mobilization. In this study, we retrospectively analyzed data from our national registry. The outcome measures were mobilization failure, CD34+ cell counts on collection day, number of apheresis procedures, and the number of collected cells. Overall, 72 patients were treated with either VCD or VTD. The mobilization failure rates were 7% and 9% (p = 0.771) and the total number of collected stem cells were 7.0 × 106 and 6.7 × 106 per kg body weight (p = 0.710) for VCD and VTD, respectively. We found no statistically significant difference between the treatment groups in the outcome measures. The addition of thalidomide to bortezomib and dexamethasone (VTD) does not adversely affect stem cell harvest in patients mobilized with G-CSF only.

Thalidomide Inhibits Human iPSC Mesendoderm Differentiation by Modulating CRBN-dependent Degradation of SALL4

Exposure to thalidomide during a critical window of development results in limb defects in humans and non-human primates while mice and rats are refractory to these effects. Thalidomide-induced teratogenicity is dependent on its binding to cereblon (CRBN), the substrate receptor of the Cul4A-DDB1-CRBN-RBX1 E3 ubiquitin ligase complex. Thalidomide binding to CRBN elicits subsequent ubiquitination and proteasomal degradation of CRBN neosubstrates including SALL4, a transcription factor of which polymorphisms phenocopy thalidomide-induced limb defects in humans. Herein, thalidomide-induced degradation of SALL4 was examined in human induced pluripotent stem cells (hiPSCs) that were differentiated either to lateral plate mesoderm (LPM)-like cells, the developmental ontology of the limb bud, or definitive endoderm. Thalidomide and its immunomodulatory drug (IMiD) analogs, lenalidomide, and pomalidomide, dose-dependently inhibited hiPSC mesendoderm differentiation. Thalidomide- and IMiD-induced SALL4 degradation can be abrogated by CRBN V388I mutation or SALL4 G416A mutation in hiPSCs. Genetically modified hiPSCs expressing CRBN E377V/V388I mutant or SALL4 G416A mutant were insensitive to the inhibitory effects of thalidomide, lenalidomide, and pomalidomide on LPM differentiation while retaining sensitivity to another known limb teratogen, all-trans retinoic acid (atRA). Finally, disruption of LPM differentiation by atRA or thalidomide perturbed subsequent chondrogenic differentiation in vitro. The data here show that thalidomide, lenalidomide, and pomalidomide affect stem cell mesendoderm differentiation through CRBN-mediated degradation of SALL4 and highlight the utility of the LPM differentiation model for studying the teratogenicity of new CRBN modulating agents.

Thalidomide induces apoptosis during early mesodermal differentiation of human induced pluripotent stem cells

Thalidomide was once administered to pregnant women as a mild sedative; however, it was subsequently shown to be strongly teratogenic. Recently, there has been renewed interest in thalidomide because of its curative effects against intractable diseases. However, the teratogenicity of thalidomide is manifested in various ways and is still not fully understood. In the present study, we evaluated the effects of thalidomide on early mesodermal differentiation by examining the differentiation of human induced pluripotent stem cells (hiPSCs). The most common symptom of thalidomide teratogenicity is limb abnormality, which led us to hypothesize that thalidomide prevents early mesodermal differentiation. Therefore, mesodermal differentiation of hiPSCs was induced over a 6-d period. To induce early mesoderm differentiation, 1 d after seeding, the cells were incubated with the small molecule compound CHIR99021 for 3 d. Thalidomide exposure was initiated at the same time as CHIR99021 treatment. After 5 d of thalidomide exposure, the hiPSCs began expressing a mesodermal marker; however, the number of viable cells decreased significantly as compared to that of control cells. We observed that the proportion of apoptotic and dead cells increased on day 2; however, the proportion of dead cells on day 5 had decreased, suggesting that the cells were damaged by thalidomide during early mesodermal differentiation (days 0-2). Our findings may help elucidate the mechanism underlying thalidomide teratogenicity and bring us closer to the safe use of this drug.