One of the challenging problems of current radio-chemotherapy is recurrence and metastasis of cancer cells that survive initial treatment. We propose that one of the unwanted effects of radiochemotherapy is the release from damaged (“leaky”) cells of nucleotides such as ATP and UTP that exert pro-metastatic functions and can directly stimulate chemotaxis of cancer cells. To address this problem in a model of human lung cancer (LC), we employed several complementary in vitro and in vivo approaches to demonstrate the role of extracellular nucleotides (EXNs) in LC cell line metastasis and tumor progression. We measured concentrations of EXNs in several organs before and after radiochemotherapy. The purinergic receptor agonists and antagonists, inhibiting all or selected subtypes of receptors, were employed in in vitro and in vivo pro-metastatic assays. We found that EXNs accumulate in several organs in response to radiochemotherapy, and RT-PCR analysis revealed that most of the P1 and P2 receptor subtypes are expressed in human LC cells. EXNs were found to induce chemotaxis and adhesion of LC cells, and an autocrine loop was identified that promotes the proliferation of LC cells. Most importantly, metastasis of these cells could be inhibited in immunodeficient mice in the presence of specific small molecule inhibitors of purinergic receptors. Based on this result, EXNs are novel pro-metastatic factors released particularly during radiochemotherapy, and inhibition of their pro-metastatic effects via purinergic signaling could become an important part of anti-metastatic treatment.

Evidence has accumulated that murine haematopoietic stem/progenitor cells (HSPCs) share several markers with the germline, a connection supported by recent reports that pituitary and gonadal sex hormones (SexHs) regulate development of murine HSPCs. It has also been reported that human HSPCs, like their murine counterparts, respond to certain SexHs (e.g. androgens). However, to better address the effects of SexHs, particularly pituitary SexHs, on human haematopoiesis, we tested for expression of receptors for pituitary SexHs, including follicle‐stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL), as well as the receptors for gonadal SexHs, including progesterone, oestrogens, and androgen, on HSPCs purified from human umbilical cord blood (UCB) and peripheral blood (PB). We then tested the functionality of these receptors in ex vivo signal transduction studies and in vitro clonogenic assays. In parallel, we tested the effect of SexHs on human mesenchymal stromal cells (MSCs). Finally, based on our observation that at least some of the UCB‐derived, CD45⁻ very small embryonic‐like stem cells (VSELs) become specified into CD45⁺ HSPCs, we also evaluated the expression of pituitary and gonadal SexH receptors on these cells. We report for the first time that human HSPCs and VSELs, like their murine counterparts, express pituitary and gonadal SexH receptors at the mRNA and protein levels. Most importantly, SexH if added to suboptimal doses of haematopoietic cytokines and growth factors enhance clonogenic growth of human HSPCs as well as directly stimulate proliferation of MSCs.

As a crucial arm of innate immunity, the complement cascade (ComC) is involved both in mobilization of normal hematopoietic stem/progenitor cells (HSPCs) from bone marrow (BM) into peripheral blood (PB) and in their homing to BM. Despite the fact that ComC cleavage fragments alone do not chemoattract normal HSPCs, we found that leukemia cell lines as well as clonogenic blasts from CML and AML patients respond robustly to C3 and C5 cleavage fragments by chemotaxis and increased adhesion. This finding was supported by the detection of C3a and C5a receptors in cells from human malignant hematopoietic cell lines and patient blasts at the mRNA (RT-PCR) and protein level (FACS) and by the demonstration that these receptors respond to stimulation by C3a and C5a by phosphorylation of p42/44 and p38 MAPK and AKT. We also found that inducible heme oxygenase 1 (HO-1) is a negative regulator of ComC-mediated trafficking of leukemic cells and that stimulation of leukemic cells by C3 or C5 cleavage fragments activates p38 MAPK, which downregulates HO-1 expression, rendering cells more mobile. We conclude that activation of the ComC in leukemia/lymphoma patients (e.g., as a result of accompanying infections) enhances the motility of malignant cells and contributes to their spread in a p38 MAPK–HO-1-dependent manner. Therefore, inhibition of p38 MAPK or upregulation of HO-1 by small-molecule modulators would have a beneficial effect on ameliorating expansion of leukemia/lymphoma cells when the ComC becomes activated.

One of side effects of chemotherapy and radiotherapy is the induction of several factors in various tissues and organs that create a pro-metastatic microenvironment for cancer cells that survive initial treatment. In the present study, we employed human ovarian cancer cell line A2780 and immunodeficient mice xenogrfat model to test effect of both ibuprofen and dexamethasone to ameliorate the therapy-induced pro-metastatic microenvironment in bone marrow, liver, and lung. In our studies, we found that total body irradiation or administration of cisplatin increases the metastatic spread of human ovarian cancer cells transplanted into immunodeficient mice compared with animals unexposed to irradiation or cisplatin. Moreover, conditioned media harvested from irradiated murine bone marrow, lung, and liver chemoattracted human ovarian cancer cells, and this chemotactic activity was inactivated by heat, suggesting a major involvement of peptide or peptide-bound chemoattractants. We also observed that human ovarian cancer cells proliferate better if exposed to cell debris harvested from irradiated murine bone marrow. Finally, the pro-metastatic microenvironment in mice induced by radio- or chemotherapy was significantly ameliorated if animals were treated at the time of radiotherapy administration with non-steroid (ibuprofen) or steroid (prednisone) anti-inflammatory drugs. In summary, we propose that a radiochemotherapy-induced, pro-metastatic microenvironment plays an important role in the metastasis of cancer cells that are resistant to treatment. Such cells have characteristics of cancer stem cells and are highly migratory, and simple, intensive, anti-inflammatory treatment by non-steroid agents to suppress induction of pro-metastatic factors after radiochemotherapy would be an interesting anti-metastatic treatment alternative.

Leukemia is one of the leading journals in hematology and oncology. It is published monthly and covers all aspects of the research and treatment of leukemia and allied diseases. Studies of normal hemopoiesis are covered because of their comparative relevance.

Nitric oxide (NO) is a gaseous free radical molecule involved in several biological processes related to inflammation, tissue damage, and infections. Based on reports that NO inhibits migration of granulocytes and monocytes, we became interested in the role of inducible NO synthetase (iNOS) in pharmacological mobilization of hematopoietic stem/progenitor cells (HSPCs) from bone marrow (BM) into peripheral blood (PB). To address the role of NO in HSPC trafficking, we upregulated or downregulated iNOS expression in hematopoietic cell lines. Next, we performed mobilization studies in iNOS^−/− mice and evaluated engraftment of iNOS^−/− HSPCs in wild type (control) animals. Our results indicate that iNOS is a novel negative regulator of hematopoietic cell migration and prevents egress of HSPCs into PB during mobilization. At the molecular level, downregulation of iNOS resulted in downregulation of heme oxygenase 1 (HO-1), and, conversely, upregulation of iNOS enhanced HO-1 activity. Since HO-1 is a negative regulator of cell migration, the inhibitory effects of iNOS identified by us can be at least partially explained by its enhancing the HO-1 level in BM cells.