Bing Cui

ROR1 Is Expressed in Human Breast Cancer and Associated with Enhanced Tumor-Cell Growth

Receptor-tyrosine-kinase-like orphan receptor 1 (ROR1) is expressed during embryogenesis and by certain leukemias, but not by normal adult tissues. Here we show that the neoplastic cells of many human breast cancers express the ROR1 protein and high-level expression of ROR1 in breast adenocarcinoma was associated with aggressive disease. Silencing expression of ROR1 in human breast cancer cell lines found to express this protein impaired their growth in vitro and also in immune-deficient mice. We found that ROR1 could interact with casein kinase 1 epsilon (CK1ε) to activate phosphoinositide 3-kinase-mediated AKT phosphorylation and cAMP-response-element-binding protein (CREB), which was associated with enhanced tumor-cell growth. Wnt5a, a ligand of ROR1, could induce ROR1-dependent signaling and enhance cell growth. This study demonstrates that ROR1 is expressed in human breast cancers and has biological and clinical significance, indicating that it may be a potential target for breast cancer therapy.

TLR4 activity is required in the resolution of pulmonary inflammation and fibrosis after acute and chronic lung injury

Pulmonary fibrosis is an inflammation-driven lung disease with a poor prognosis and no cure. Here we report that basal toll-like receptor 4 (TLR4) activity is critical for the resolution of acute and chronic inflammation and pulmonary fibrosis in mouse models of lung injury. We found that genetic or pharmacologic inhibition of TLR4 exacerbates bleomycin-induced pulmonary inflammation, fibrosis, dysfunction, and animal death through promoting formation of an immunosuppressive tissue microenvironment and attenuating autophagy-associated degradation of collagen and cell death in the fibrotic lung tissues. In contrast, pharmacologic activation of TLR4 resulted in a quick resolution of acute inflammation, reversed the established pulmonary fibrosis, improved lung function, and rescued mice from death. Similarly, blocking TLR4 impaired the resolution of silica-induced chronic inflammation and fibrosis. Importantly, altering autophagic activity could reverse the TLR4-regulated lung inflammation, fibrosis, dysfunction, and animal death. Rapamycin, an autophagy activator, reversed the effects of TLR4 antagonism. In contrast, inhibition of autophagy by 3-methyladenine reversed the proresolving and antifibrotic roles of TLR4 agonists and increased animal death. These results not only highlight a pivotal role for TLR4-mediated basal immunity, particularly autophagic activity, in the proresolution of inflammation and fibrosis after chemical-induced lung injury but also provide proof for the concept for activating TLR4 signaling, particularly TLR4-mediated autophagy, as a novel therapeutic strategy against chronic fibroproliferative diseases that are unresponsive to current therapy.

Blocking TLR2 Activity Attenuates Pulmonary Metastases of Tumor

Background Metastasis is the most pivotal cause of mortality in cancer patients. Immune tolerance plays a crucial role in tumor progression and metastasis. Methods and Findings In this study, we investigated the potential roles and mechanisms of TLR2 signaling on tumor metastasis in a mouse model of intravenously injected B16 melanoma cells. Multiple subtypes of TLRs were expressed on B16 cells and several human cancer cell lines; TLR2 mediated the invasive activity of these cells. High metastatic B16 cells released more heat shock protein 60 than poor metastatic B16-F1 cells. Importantly, heat shock protein 60 released by tumor cells caused a persistent activation of TLR2 and was critical in the constitutive activation of transcription factor Stat3, leading to the release of immunosuppressive cytokines and chemokines. Moreover, targeting TLR2 markedly reduced pulmonary metastases and increased the survival of B16-bearing mice by reversing B16 cells induced immunosuppressive microenvironment and restoring tumor-killing cells such as CD8+ T cells and M1 macrophages. Combining an anti-TLR2 antibody and a cytotoxic agent, gemcitabine, provided a further improvement in the survival of tumor-bearing mice. Conclusions and Significance Our results demonstrate that TLR2 is an attractive target against metastasis and that targeting immunosuppressive microenvironment using anti-TLR2 antibody is a novel therapeutic strategy for combating a life-threatening metastasis.

MicroRNA-155 influences B-cell receptor signaling and associates with aggressive disease in chronic lymphocytic leukemia

High-level leukemia cell expression of micro-RNA 155 (miR-155) is associated with more aggressive disease in patients with chronic lymphocytic leukemia (CLL), including those cases with a low-level expression of ζ-chain-associated protein of 70 kD. CLL with high-level miR-155 expressed lower levels of Src homology-2 domain-containing inositol 5-phosphatase 1 and were more responsive to B-cell receptor (BCR) ligation than CLL with low-level miR-155. Transfection with miR-155 enhanced responsiveness to BCR ligation, whereas transfection with a miR-155 inhibitor had the opposite effect. CLL in lymphoid tissue expressed higher levels of miR155HG than CLL in the blood of the same patient. Also, isolated CD5(bright)CXCR4(dim) cells, representing CLL that had been newly released from the microenvironment, expressed higher levels of miR-155 and were more responsive to BCR ligation than isolated CD5(dim)CXCR4(bright) cells of the same patient. Treatment of CLL or normal B cells with CD40-ligand or B-cell-activating factor upregulated miR-155 and enhanced sensitivity to BCR ligation, effects that could be blocked by inhibitors to miR-155. This study demonstrates that the sensitivity to BCR ligation can be enhanced by high-level expression of miR-155, which in turn can be induced by crosstalk within the tissue microenvironment, potentially contributing to its association with adverse clinical outcome in patients with CLL.

The Onco-Embryonic Antigen ROR1 Is Expressed by a Variety of Human Cancers

ROR1 is an orphan-receptor tyrosine-kinase-like surface antigen that is expressed by many tissues during embryogenesis, some B-cell malignancies, and various cancer cell lines but not by virtually all normal adult tissues. Here, we report that large proportions of many different human cancers also express ROR1, particularly those cancers that have high-grade histology. Primary cancers that expressed ROR1 more commonly expressed high levels of phosphorylated AKT (p-AKT) and phosphorylated cAMP response element binding-factor (p-CREB) than similar cancers that lacked expression of ROR1. Induced expression of ROR1 could enhance basal p-AKT and p-CREB levels and could promote the growth of a cancer cell line, MEC1. Conversely, silencing ROR1 resulted in lower levels of p-AKT and p-CREB, which was associated with impaired tumor cell growth. In summary, this study found that many different human cancers express ROR1 and that ROR1 may play a functional role in promoting tumor cell growth, suggesting that this orphan-receptor tyrosine-kinase-like protein may be a potential target for therapy directed against a variety of human cancers.

Targeting TLR2 Attenuates Pulmonary Inflammation and Fibrosis by Reversion of Suppressive Immune Microenvironment

Pulmonary fibrosis is a consequence of chronic lung injury and is associated with a high mortality. Despite the pathogenesis of pulmonary fibrosis remaining as an enigma, immune responses play a critical role in the deregulation of wound healing process after lung injury, which leads to fibrosis. Accumulating evidence argues the rationales for current treatments of pulmonary fibrosis using immunosuppressive agents such as corticosteroids. In this study, we report that bleomycin (BLM), a well-known fibrogenic agent functioning as a TLR2 agonist, induced the maturation of dendritic cells and release of cytokines. The BLM activation of TLR2 mediated a time-dependent alteration of immune responses in the lung. These responses resulted in an increase in the tissue-infiltrating proinflammatory cells and cytokines in the early period initially following BLM exposure and an increase in the tissue-infiltrating suppressive immune cells and factors during the later period following BLM exposure. TLR2 deficiency, however, reduced pulmonary inflammation, injury, and subsequently attenuated pulmonary fibrosis. Targeting TLR2 by a TLR2-neutralizing Ab not only markedly decreased animal death but also protected animals from the development of pulmonary fibrosis and reversed the established pulmonary fibrosis through regulating BLM-induced immunosuppressive microenvironments. Our studies suggest that TLR2 is a promising target for the development of therapeutic agents against pulmonary fibrosis and that eliminating immunosuppressive cells and factors via immunostimulants is a novel strategy for fibro-proliferative diseases. Moreover, combining BLM with an anti-TLR2 Ab or TLR2 antagonist for cancer therapy will improve the BLM therapeutic profile by enhancing anti-cancer efficacy and reducing systemic inflammation and pulmonary fibrosis.

Ovarian cancer stem cells express ROR1, which can be targeted for anti–cancer-stem-cell therapy

Significance This study demonstrates that the oncoembryonic surface antigen, receptor tyrosine kinase-like orphan receptor 1 (ROR1), is expressed on human ovarian cancer stem cells (CSCs), on which it seems to play a functional role in promoting migration/invasion or spheroid formation in vitro and tumor engraftment in immune-deficient mice. Treatment with a humanized mAb specific for ROR1 (UC-961) could inhibit the capacity of ovarian cancer cells to migrate, form spheroids, or engraft immune-deficient mice. Moreover, such treatment inhibited the growth of tumor xenografts, which in turn had a reduced capacity to engraft immune-deficient mice and were relatively depleted of cells with features of CSC, suggesting that treatment with UC-961 could impair CSC renewal. Collectively, these studies indicate that ovarian CSCs express ROR1, which may be targeted for anti-CSC therapy. Although initially responsive to chemotherapy, many patients with ovarian cancer subsequently develop relapsed and potentially fatal metastatic disease, which is thought to develop from cancer stem cells (CSCs) that are relatively resistant to conventional therapy. Here, we show that CSCs express a type I receptor tyrosine kinase-like orphan receptor (ROR1), which is expressed during embryogenesis and by many different cancers, but not normal postpartum tissues. Ovarian cancers with high levels of ROR1 had stem cell-like gene-expression signatures. Furthermore, patients with ovarian cancers with high levels of ROR1 had higher rates of relapse and a shorter median survival than patients with ovarian cancers that expressed low-to-negligible amounts of ROR1. We found that ROR1-positive (ROR1+) cells isolated from primary tumor-derived xenografts (PDXs) also expressed aldehyde dehydrogenase 1 (ALDH1) and had a greater capacity to form spheroids and to engraft immune-deficient mice than did ROR1-negative (ROR1Neg) ovarian cancer cells isolated from the same tumor population. Treatment with UC-961, an anti-ROR1 mAb, or shRNA silencing of ROR1 inhibited expression of the polycomb ring-finger oncogene, Bmi-1, and other genes associated with the epithelial–mesenchymal transition. Moreover, shRNA silencing of ROR1, depletion of ROR1+ cells, or treatment with UC-961 impaired the capacity of ovarian cancer cells to form spheroids or tumor xenografts. More importantly, treatment with anti-ROR1 affected the capacity of the xenograft to reseed a virgin mouse, indicating that targeting ROR1 may affect CSC self-renewal. Collectively, these studies indicate that ovarian CSCs express ROR1, which contributes to their capacity to form tumors, making ROR1 a potential target for the therapy of patients with ovarian cancer.

Targeting ROR1 Inhibits Epithelial-Mesenchymal Transition and Metastasis

Metastasis is responsible for 90% of cancer-related deaths. Strategies are needed that can inhibit the capacity of cancer cells to migrate across the anatomic barriers and colonize distant organs. Here, we show an association between metastasis and expression of a type I receptor tyrosine kinase-like orphan receptor, ROR1, which is expressed during embryogenesis and by various cancers, but not by normal postpartum tissues. We found that expression of ROR1 associates with the epithelial-mesenchymal transition (EMT), which occurs during embryogenesis and cancer metastasis. Breast adenocarcinomas expressing high levels of ROR1 were more likely to have gene expression signatures associated with EMT and had higher rates of relapse and metastasis than breast adenocarcinomas expressing low levels of ROR1. Suppressing expression of ROR1 in metastasis-prone breast cancer cell lines, MDA-MB-231, HS-578T, or BT549, attenuated expression of proteins associated with EMT (e.g., vimentin, SNAIL-1/2, and ZEB1), enhanced expression of E-cadherin, epithelial cytokeratins (e.g., CK-19), and tight junction proteins (e.g., ZO-1), and impaired their migration/invasion capacity in vitro and the metastatic potential of MDA-MB-231 cells in immunodeficient mice. Conversely, transfection of MCF-7 cells to express ROR1 reduced expression of E-cadherin and CK-19, but enhanced the expression of SNAIL-1/2 and vimentin. Treatment of MDA-MB-231 with a monoclonal antibody specific for ROR1 induced downmodulation of vimentin and inhibited cancer cell migration and invasion in vitro and tumor metastasis in vivo. Collectively, this study indicates that ROR1 may regulate EMT and metastasis and that antibodies targeting ROR1 can inhibit cancer progression and metastasis.

Wnt5a induces ROR1/ROR2 heterooligomerization to enhance leukemia chemotaxis and proliferation

Evolutionarily conserved receptor tyrosine kinase–like orphan receptor-1 and -2 (ROR1/2) are considered distinct receptors for Wnt5a and are implicated in noncanonical Wnt signaling in organogenesis and cancer metastasis. We found that Wnt5a enhanced proliferation and migration of chronic lymphocytic leukemia (CLL) cells and that these effects were blocked by the humanized anti-ROR1 mAb cirmtuzumab (UC-961). Treatment of CLL cells with Wnt5a induced ROR1 to oligomerize with ROR2 and recruit guanine exchange factors (GEFs), which activated Rac1 and RhoA; siRNA-mediated silencing of either ROR1 or ROR2 or treatment with UC-961 inhibited these effects. Using the ROR1-deficient CLL cell line MEC1, we demonstrated that ectopic ROR1 expression induced ROR1/ROR2 heterooligomers, which recruited GEFs, and enhanced proliferation, cytokine-directed migration, and engraftment potential of MEC1 cells in immune-deficient mice. Notably, treatment with UC-961 inhibited engraftment of ROR1+ leukemia cells in immune-competent ROR1-transgenic mice. Molecular analysis revealed that the extracellular Kringle domain is required for ROR1/ROR2 heterooligomerization and the cysteine-rich domain or intracellular proline-rich domain is required for Wnt5a-induced recruitment of GEFs to ROR1/ROR2. This study identifies an interaction between ROR1 and ROR2 that is required for Wnt5a signaling that promotes leukemia chemotaxis and proliferation.

Lenalidomide inhibits the proliferation of CLL cells via a cereblon/ p21 WAF1/Cip1 -dependent mechanism independent of functional p53

Lenalidomide has demonstrated clinical activity in patients with chronic lymphocytic leukemia (CLL), even though it is not cytotoxic for primary CLL cells in vitro. We examined the direct effect of lenalidomide on CLL-cell proliferation induced by CD154-expressing accessory cells in media containing interleukin-4 and -10. Treatment with lenalidomide significantly inhibited CLL-cell proliferation, an effect that was associated with the p53-independent upregulation of the cyclin-dependent kinase inhibitor, p21(WAF1/Cip1) (p21). Silencing p21 with small interfering RNA impaired the capacity of lenalidomide to inhibit CLL-cell proliferation. Silencing cereblon, a known molecular target of lenalidomide, impaired the capacity of lenalidomide to induce expression of p21, inhibit CD154-induced CLL-cell proliferation, or enhance the degradation of Ikaros family zinc finger proteins 1 and 3. We isolated CLL cells from the blood of patients before and after short-term treatment with low-dose lenalidomide (5 mg per day) and found the leukemia cells were also induced to express p21 in vivo. These results indicate that lenalidomide can directly inhibit proliferation of CLL cells in a cereblon/p21-dependent but p53-independent manner, at concentrations achievable in vivo, potentially contributing to the capacity of this drug to inhibit disease-progression in patients with CLL.