Objectives: The focus of this study was to determine the dedicator of cytokinesis 2 (DOCK2), extracellular signal‐regulated kinase 1/2 (ERK1/2), c‐Jun N‐terminal kinase‐1 (JNK) and Akt signals involved in CXCL13‐mediated prostate cancer (PCa) cell invasion and proliferation. Materials and methods: Androgen‐sensitive (LNCaP), hormone‐refractory (PC3) cells and normal cells (RWPE‐1) were used to determine CXCL13‐mediated PCa cell invasion and proliferation. Immuno‐blotting, fast activated cell‐based (FACE) ELISA, caspase activity, cell invasion and proliferation assays were performed to ascertain some of the signalling events involved in PCa cell proliferation and invasion. Results: Unlike androgen‐sensitive LNCaP cells, we report for the first time that the hormone‐refractory cell line, PC3, expresses DOCK2. CXCL13‐mediated LNCaP and PC3 cell invasion was regulated by Akt and ERK1/2 activation in a DOCK2‐independent fashion. CXCL13 also promoted LNCaP cell proliferation in a JNK‐dependent fashion even in the absence of DOCK2. In contrast, CXCL13 induced PC3 cell proliferation through JNK activation, which required DOCK2. Conclusions: Our results show CXCL13‐mediated PCa cell invasion requires Akt and ERK1/2 activation and suggests a new role for DOCK2 in proliferation of hormone‐refractory CXCR5‐positive PCa cells.

Background: Most prostate cancer (PCa)-related deaths are due to metastasis, which is mediated in part by chemokine receptor and corresponding ligand interaction. We have previously shown that PCa tissue and cell lines express high levels of the chemokine receptor CXCR5, than compared to their normal counterparts, and interaction of CXCR5 with its specific ligand (CXCL13) promoted PCa cell invasion, migration, and differential matrix metalloproteinase (MMP) expression. This study dissects some of the molecular mechanisms following CXCL13-CXCR5 interaction that mediate PCa cell migration and invasion. Results: Using Western blot analysis, kinase-specific cell-based ELISAs, and migration and invasion assays, we show that PCa cell lines differentially express phosphoinositide-3 kinase (PI3K) catalytic subunit isoforms and dedicator of cytokinesis 2 (DOCK2). Specifically, we show that PC3 and normal prostatic epithelial (RWPE-1), but not LNCaP cell lines expressed DOCK2, while RWPE, PC3, and LNCaP cell lines expressed PI3K-p110α and -p110β. Moreover, PC3 selectively expressed PI3K-p110γ, but LNCaP and RWPE cell lines expressed PI3Kp110δ. CXCL13 caused CXCR5-dependent activation of the PI3Kp85α in LNCaP cells, and p85α as well as -p101 in PC3 cells. CXCL13-CXCR5 interaction regulated LNCaP and PC3 cell migration and invasion through extracellular signal-regulated kinase 1/2 (ERK1/2) activation that was primarily dependent on the PI3Kp110 isoform(s), Src, and focal adhesion kinase (FAK), but not DOCK2. Conclusions: While additional studies will be needed to determine the PI3K-independent (i.e., DOCK2-mediated) and -dependent events that dictate PCa cell responsiveness to CXCL13, these data provide evidence of the existence of cell type- and stimulus-specific signaling events that support migration and invasion of PCa cells.

Despite recent advances in treatment and management of prostate cancer (PCa), it remains the second leading cause of cancer‐related deaths among men in the US. Chemotherapy is one of the treatment alternatives for hormone refractory metastatic PCa. However, current chemotherapeutic regimens provide palliative benefit but relatively modest survival advantage primarily due to chemo‐resistance and upregulated antiapoptotic machineries in PCa cells. Therefore, blocking the mechanisms responsible for suppression of apoptosis might improve current chemotherapeutic regimens. In this study, we show that CC chemokine receptor‐9 (CCR9) and its natural ligand CCL25 interaction upregulates antiapoptotic proteins (i.e., PI3K, AKT, ERK1/2 and GSK‐3β) and downregulate activation of caspase‐3 in PCa cells. Significant downregulation of these CCR9‐mediated antiapoptotic proteins in the presence of a PI3K inhibitor (wortmannin), further suggests that the antiapoptotic action of CCR9 is primarily regulated through PI3K. Furthermore, the cytotoxic effect of etoposide was significantly inhibited in the presence of CCL25, and this inhibitory effect of CCL25 was abrogated when CCR9‐CCL25 interaction was blocked using anti‐CCR9 monoclonal antibodies. In conformation to these in vitro studies, significant reduction in tumor burden was found in mice receiving CCL25 neutralizing antibodies and etoposide together as compared to both as a single agent. These results suggest that the CCR9‐CCL25 axis mediates PI3K/AKT‐dependent antiapoptotic signals in PCa cells and could be a possible reason for low apoptosis and modest chemotherapeutic response. Therefore, targeting CCR9‐CCL25 axis with cytotoxic agents may provide better therapeutic outcomes than using cytotoxic agents alone.

Poor clinical outcome of lung cancer (LuCa) is primarily due to lack of knowledge about specific molecules involved in its progression and metastasis. In this study, we for the first time show the clinical and biological significance of CC chemokine receptor-9 (CCR9) in non-small cell lung cancer (NSCLC). Expression of CCR9 and CCL25, the only natural ligand of CCR9, was significantly higher (p < 0.0001) in NSCLC tissues and serum respectively, compared to their respective controls. Interestingly, expression of both CCR9 and CCL25 was significantly higher in adenocarcinomas (ACs) compared to squamous cell carcinomas (SCCs) (p = 0.04, and p < 0.0001). Similar to tissues, AC and SCC cell lines were positive for CCR9 expression. Despite of marginal difference in CCR9 expression, AC cells showed higher migratory and invasive potential in response to CCL25, compared to SCC cells. This differential biological response of AC cells was primarily due to differential expression of matrix metalloproteinases and tissue inhibitor of metalloproteinases under the influence of CCL25. Our results suggest CCR9 as a potential target for developing new treatment modality for NSCLC. Additionally, differential serum CCL25 level in ACs and SCCs, two NSCLC subtypes, suggest its potential as a non-invasive diagnostic/prognostic biomarker.