High serum levels of IL-6 correlate with poor outcome in breast cancer patients. However, no data are available on the relationship between IL-6 and mammary stem/progenitor cells, which may fuel the genesis of breast cancer in vivo. Herein, we address this issue in the MCF-7 breast cancer cell line and in primary human mammospheres (MS), multicellular structures enriched in stem/progenitor cells of the mammary gland. MS from node invasive breast carcinoma tissues expressed IL-6 mRNA at higher levels than did MS from matched non-neoplastic mammary glands. In addition, IL-6 mRNA was detected only in basal-like breast carcinoma tissues, an aggressive breast carcinoma variant showing stem cell features. IL-6 treatment triggered Notch-3–dependent upregulation of the Notch ligand Jagged-1 and promotion of MS and MCF-7–derived spheroid growth. Moreover, IL-6 induced Notch-3–dependent upregulation of the carbonic anhydrase IX gene and promoted a hypoxia-resistant/invasive phenotype in MCF-7 cells and MS. Finally, autocrine IL-6 signaling relied upon Notch-3 activity to sustain the aggressive features of MCF-7–derived hypoxia-selected cells. In conclusion, these data support the hypothesis that IL-6 induces malignant features in Notch-3–expressing stem/progenitor cells from human ductal breast carcinoma and normal mammary gland.

Lifestyle factors are responsible for a considerable portion of cancer incidence worldwide, but credible estimates from the World Health Organization and the International Agency for Research on Cancer (IARC) suggest that the fraction of cancers attributable to toxic environmental exposures is between 7% and 19%. To explore the hypothesis that low-dose exposures to mixtures of chemicals in the environment may be combining to contribute to environmental carcinogenesis, we reviewed 11 hallmark phenotypes of cancer, multiple priority target sites for disruption in each area and prototypical chemical disruptors for all targets, this included dose-response characterizations, evidence of low-dose effects and cross-hallmark effects for all targets and chemicals. In total, 85 examples of chemicals were reviewed for actions on key pathways/mechanisms related to carcinogenesis. Only 15% (13/85) were found to have evidence of a dose-response threshold, whereas 59% (50/85) exerted low-dose effects. No dose-response information was found for the remaining 26% (22/85). Our analysis suggests that the cumulative effects of individual (non-carcinogenic) chemicals acting on different pathways, and a variety of related systems, organs, tissues and cells could plausibly conspire to produce carcinogenic synergies. Additional basic research on carcinogenesis and research focused on low-dose effects of chemical mixtures needs to be rigorously pursued before the merits of this hypothesis can be further advanced. However, the structure of the World Health Organization International Programme on Chemical Safety ‘Mode of Action’ framework should be revisited as it has inherent weaknesses that are not fully aligned with our current understanding of cancer biology.

An emerging area in environmental toxicology is the role that chemicals and chemical mixtures have on the cells of the human immune system. This is an important area of research that has been most widely pursued in relation to autoimmune diseases and allergy/asthma as opposed to cancer causation. This is despite the well-recognized role that innate and adaptive immunity play as essential factors in tumorigenesis. Here, we review the role that the innate immune cells of inflammatory responses play in tumorigenesis. Focus is placed on the molecules and pathways that have been mechanistically linked with tumor-associated inflammation. Within the context of chemically induced disturbances in immune function as co-factors in carcinogenesis, the evidence linking environmental toxicant exposures with perturbation in the balance between pro- and anti-inflammatory responses is reviewed. Reported effects of bisphenol A, atrazine, phthalates and other common toxicants on molecular and cellular targets involved in tumor-associated inflammation (e.g. cyclooxygenase/prostaglandin E₂, nuclear factor kappa B, nitric oxide synthesis, cytokines and chemokines) are presented as example chemically mediated target molecule perturbations relevant to cancer. Commentary on areas of additional research including the need for innovation and integration of systems biology approaches to the study of environmental exposures and cancer causation are presented.

Nowadays, no data are available concerning the potential use of dual cyclooxygenase (COX)/5-lipoxygenase (LOX) inhibitors as anticancer agents in colon cancer treatment. Here, we report, for the first time, that the dual COX/5-LOX inhibitor licofelone triggers apoptosis in a dose- and time-dependent manner in HCA-7 colon cancer cells. Induction of apoptosis was related to the recruitment of the intrinsic mitochondrial apoptotic pathway, as shown by loss in mitochondrial membrane potential, cytochrome c release, caspase-9 and 3 activation and poly-(ADP-ribose)polymerase-1 cleavage. Moreover, licofelone induced the cleavage of the full-length p21^Bax into p18^Bax, a more potent inducer of the apoptotic process than the uncleaved form. Pre-treatment of HCA-7 cells with the pan-caspase inhibitor z-VAD-fmk significantly blocked licofelone-induced apoptosis, confirming that this process occurred primarily in a caspase-dependent pathway. We also present evidences that licofelone was able to affect the arachidonic acid (AA) cascade, as it blocked the activity of 5-LOX and COX enzymes, and it induced, through the phosphorylation of cytoplasmic phospholipase A₂ (cPLA₂), the release of unesterified AA from HCA-7 membrane phospholipids. However, apoptosis induction was not related to the ability of licofelone to affect the AA cascade, since neither exogenous prostaglandin E₂ and leukotriene B₄ addition, nor pharmacological inhibition of cPLA₂, was able to rescue HCA-7 cells from apoptosis. Even if further studies are needed to clarify the mechanism of licofelone-induced apoptosis, this study suggests that this drug, as well as similar dual COX/5-LOX inhibitors, may represent a novel and promising approach in colon cancer treatment.