Cabanas Hélène, Harnois Thomas, Magaud Christophe, Cousin Laëtitia, Constantin Bruno, Bourmeyster Nicolas, Déliot Nadine
Laboratoire de Signalisation et Transports Ioniques Membranaires (STIM) ERL CNRS 7368, Equipe Calcium et Microenvironnement des Cellules Souches (CMCS), Université de Poitiers, 86073 Poitiers, France.
Laboratoire de Signalisation et Transports Ioniques Membranaires (STIM) ERL CNRS 7368, Equipe Transferts Ioniques et Rythmicité Cardiaque (TIRC), Université de Poitiers, 86073 Poitiers, France.
Oncotarget. 2018 May 29;9(41):26309-26327. doi: 10.18632/oncotarget.25241.
Chronic myeloid leukemia (CML) results from hematopoietic stem cell transformation by the chimeric oncogene, encoding a 210 kDa protein with constitutive tyrosine kinase activity. In spite of the efficiency of tyrosine kinase inhibitors (TKI; Imatinib), other strategies are explored to eliminate CML leukemia stem cells, such as calcium pathways.
In this work, we showed that Store-Operated Calcium Entry (SOCE) and thrombin induced calcium influx were decreased in Bcr-Abl expressing 32d cells (32d-p210). The 32d-p210 cells showed modified Orai1/STIM1 ratio and reduced TRPC1 expression that could explain SOCE reduction. Decrease in SOCE and thrombin induced calcium entry was associated to reduced Nuclear Factor of Activated T cells (NFAT) nucleus translocation in 32d-p210 cells. We demonstrated that SOCE blockers enhanced cell mobility of 32d-p210 cells and reduced the proliferation rate in both 32d cell lines. TKI treatment slightly reduced the thrombin-induced response, but imatinib restored SOCE to the wild type level. Bcr-Abl is also known to deregulate Protein Kinase C (PKC), which was described to modulate calcium entries. We showed that PKC enhances SOCE and thrombin induced calcium entries in control cells while this effect is lost in Bcr-Abl-expressing cells.
The tyrosine kinase activity seems to regulate calcium entries probably not directly but through a global cellular reorganization involving a PKC pathway. Altogether, calcium entries are deregulated in Bcr-Abl-expressing cells and could represent an interesting therapeutic target in combination with TKI.
慢性髓性白血病（CML）是由嵌合致癌基因导致造血干细胞转化引起的，该基因编码一种具有组成型酪氨酸激酶活性的210 kDa蛋白。尽管酪氨酸激酶抑制剂（TKI；伊马替尼）疗效显著，但仍在探索其他策略来消除CML白血病干细胞，如钙信号通路。
在本研究中，我们发现表达Bcr-Abl的32d细胞（32d-p210）中，钙库操纵性钙内流（SOCE）和凝血酶诱导的钙内流减少。32d-p210细胞显示Orai1/STIM1比例改变以及TRPC1表达降低，这可以解释SOCE的减少。SOCE和凝血酶诱导的钙内流减少与32d-p210细胞中活化T细胞核因子（NFAT）核转位减少有关。我们证明SOCE阻滞剂增强了32d-p210细胞的迁移能力，并降低了两种32d细胞系的增殖率。TKI治疗略微降低了凝血酶诱导的反应，但伊马替尼将SOCE恢复到野生型水平。已知Bcr-Abl还会使蛋白激酶C（PKC）失调，而PKC被描述为可调节钙内流。我们发现PKC增强了对照细胞中的SOCE和凝血酶诱导的钙内流，而在表达Bcr-Abl的细胞中这种作用消失。
酪氨酸激酶活性似乎可能并非直接调节钙内流，而是通过涉及PKC途径的整体细胞重组来调节。总之，表达Bcr-Abl的细胞中钙内流失调，可能是与TKI联合使用的一个有吸引力的治疗靶点。
