RESUMO
CCL18 and CXCL12 are homeostatic chemokines with high constitutive concentrations in serum. Elevated levels of CCL18 have been described in various diseases including childhood acute lymphocytic leukemia (ALL) but its functions remain poorly characterized. Its receptor has not been identified, but functional cellular responses like lymphocyte chemotaxis have been described. CXCL12 is a pivotal chemokine for hematopoiesis and B cell homing processes. We demonstrate that CCL18 interferes with CXCL12-mediated pre-B ALL cell activation. CXCL12-induced calcium mobilization, chemotaxis, pseudo-emperipolesis and cellular proliferation could be significantly reduced by CCL18 in pre-B ALL cell lines. The results could be observed in primary cells from patients suffering from pre-B ALL, but not in cells from patients suffering from common ALL. Direct effects of CCL18 on the receptor for CXCL12, CXCR4, could be excluded. Moreover, we found that CCL18 modulations of CXCL12-induced responses are mediated through the chemokine-like receptor GPR30. CCL18 bound to GPR30 expressing cells, and antibodies against GPR30 abolished this binding as well as CCL18-mediated functional effects. We also observed that, CCL18 interferes with the activation of GPR30 by previously identified ligands (17ß-estradiol and chemical agonists). We therefore suggest that CCL18 is an important modulator of CXCR4-dependent responses in pre-B ALL cells via interactions with GPR30.
Assuntos
Quimiocinas CC/metabolismo , Leucemia-Linfoma Linfoblástico de Células Precursoras B/imunologia , Células Precursoras de Linfócitos B/imunologia , Receptores CXCR4/metabolismo , Transdução de Sinais , Animais , Apoptose , Células COS , Sinalização do Cálcio , Linhagem Celular Tumoral , Proliferação de Células , Quimiocina CXCL12/metabolismo , Quimiotaxia de Leucócito , Chlorocebus aethiops , Estradiol/metabolismo , Antagonistas de Estrogênios/farmacologia , Humanos , Ligantes , Ativação Linfocitária , Leucemia-Linfoma Linfoblástico de Células Precursoras B/patologia , Células Precursoras de Linfócitos B/efeitos dos fármacos , Células Precursoras de Linfócitos B/patologia , Receptores de Estrogênio , Receptores Acoplados a Proteínas G/antagonistas & inibidores , Receptores Acoplados a Proteínas G/genética , Receptores Acoplados a Proteínas G/metabolismo , Proteínas Recombinantes/metabolismo , Transdução de Sinais/efeitos dos fármacos , TransfecçãoRESUMO
Small cell lung cancer (SCLC) is an aggressive, rapidly metastasising tumour. Previously, we demonstrated the influence of CXCL12-CXCR4 interaction on processes involved in metastasis and chemoresistance in SCLC. We show here that STAT3 is expressed in both primary SCLC tumour tissues and SCLC cell lines. We investigated the function of STAT3 upon CXCL12 stimulation in SCLC cell lines. Small cell lung cancer cell lines present constitutive phosphorylation of STAT3, and in the reference cell lines NCI-H69 and NCI-H82 constitutive phosphorylation was further increased by CXCL12 stimulation. Further investigating this signalling cascade, we showed that it involves interactions between CXCR4 and JAK2 in both cell lines. However CXCL12-induced adhesion to VCAM-1 could be completely inhibited by the JAK2 inhibitor AG490 only in NCI-H82. Furthermore, CXCR4 antagonist but not AG490 inhibited cell adhesion whereas both antagonisms were shown to inhibit growth of the cells in soft agar, indicating the central involvement of this signalling in anchorage-independent growth of SCLC cells. Most interestingly, while using primary tumour material, we observed that in contrast to non-small-cell lung cancer samples from primary tumour tissues, all analysed samples from SCLC were strongly positive for tyrosine-phosphorylated STAT3. Taken together, these data indicate that STAT3 is constitutively phosphorylated in SCLC and is important in SCLC growth and spreading thus presenting an interesting target for therapy.
