癌症幹細胞 (cancer stem cells, CSCs) 為腫瘤中一群具有腫瘤生成、抗藥性以及促進腫瘤轉移的細胞。研究指出骨髓間質幹細胞 (bone-derived mesenchymal stem cell, BM-MSCs) 在癌症幹細胞利基扮演重要的角色，並能調控癌細胞轉移。此研究發現肺癌細胞中有兩組癌細胞，分別對骨髓間質幹細胞所培養的條件培養液 (MSC-conditioned medium, MSC-CM) 有不同的反應。具上皮細胞型態的LM癌細胞經條件培養液培養後，其STAT3位於Y705的磷酸化有上升的情形，並加強了骨髓間質幹細胞所誘發的上皮-間質轉換 (epithelial-mesenchymal transition, EMT) 及癌症幹性 (cancer stemness)；而在間質型態的HM20癌細胞則觀察到，間質幹細胞所分泌的調控物質增加了HM20中STAT3-S727的磷酸化。STAT3-S727磷酸化同時也強化了由骨髓間質幹細胞所誘發的間質-上皮轉換 (mesenchymal- epithelial transition, MET) 以及癌症幹性的維持。總結上述實驗，此研究發現骨髓間質幹細胞經由STAT3的活化，調控同一細胞株中兩群不同的癌症細胞，以誘發癌症轉移以及維持癌症幹性。

Cancer stem cells (CSCs) are a small subpopulation of cancer cells known to initiate tumor growth, lead to drug resistance and drive tumor metastasis. Studies have shown that bone marrow-derived mesenchymal stem cells (BM-MSCs) contribute to cancer stem cell niche and can regulate cancer metastasis. Our research indicated that two heterogenous subgroups of cancer cells in tumor responsed differently upon MSC-conditional medium (MSC-CM) treatment. MSC-CM elevated STAT3-Y705 phosphorylation in epithelial-type LM cells, and pY705-STAT3 took part in MSC-induced EMT and CSC property induction. STAT3-S727 phosphorylation was enhanced in mesenchymal-type HM20 cells, and contributed to MSC-induced proliferation, MET, and CSC property maintenance. To sum up, we demonstrated that MSCs can induce two-step metastasis cycle on two heterogenous subgroups derived from the same cancer cell line through STAT3-elicited promotion of CSC phenotype.

Introduction 1
Tumor heterogeneity and cancer stem cells 1
Cancer progression and metastasis 2
Mesenchymal stem cell and the cancer stem cell niche 3
STAT3 and cancer stemness 4
Material and Method 6
Cell culture 6
1. Cell passage 6
Cell transfection 6
1. Electroporation 6
2. Lipofectamine 2000 6
Western Blotting 7
1. Protein lysate extraction 7
2. Western blotting 7
mRNA expression 8
1. Total RNA extraction 8
2. Reverse transcription 8
3. cDNA electrophoresis 8
Immunofluorescence 9
Luciferase assay 9
Immunohistochemistry 9
Results 11
Characterization of wildtype and mutant STAT3 11
Generation of two subtypes of cancer cells 12
pY705-STAT3 enhances MSCs-induced EMT on LM cells 12
pY705-STAT3 enhances MSCs-induced cancer stemness on LM cells 13
pS727-STAT3 enhanced MSCs-induced MET and cancer stemness on HM20 cells 13
Elevated phosphorylation of Y705- and S727-STAT3 is of clinical significance 14
Discussion 15
References 19
Figures 25

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