Exposure limits: the underestimation of absorbed cell phone radiation, especially in children.

The existing cell phone certification process uses a plastic model of the head called the Specific Anthropomorphic Mannequin (SAM), representing the top 10% of U.S. military recruits in 1989 and greatly underestimating the Specific Absorption Rate (SAR) for typical mobile phone users, especially children. A superior computer simulation certification process has been approved by the Federal Communications Commission (FCC) but is not employed to certify cell phones. In the United States, the FCC determines maximum allowed exposures. Many countries, especially European Union members, use the "guidelines" of International Commission on Non-Ionizing Radiation Protection (ICNIRP), a non governmental agency. Radiofrequency (RF) exposure to a head smaller than SAM will absorb a relatively higher SAR. Also, SAM uses a fluid having the average electrical properties of the head that cannot indicate differential absorption of specific brain tissue, nor absorption in children or smaller adults. The SAR for a 10-year old is up to 153% higher than the SAR for the SAM model. When electrical properties are considered, a child's head's absorption can be over two times greater, and absorption of the skull's bone marrow can be ten times greater than adults. Therefore, a new certification process is needed that incorporates different modes of use, head sizes, and tissue properties. Anatomically based models should be employed in revising safety standards for these ubiquitous modern devices and standards should be set by accountable, independent groups.

IL-18-induced CD83+CCR7+ NK helper cells.

In addition to their cytotoxic activities, natural killer (NK) cells can have immunoregulatory functions. We describe a distinct "helper" differentiation pathway of human CD56+CD3- NK cells into CD56+/CD83+/CCR7+/CD25+ cells that display high migratory responsiveness to lymph node (LN)-associated chemokines, high ability to produce interferon-gamma upon exposure to dendritic cell (DC)- or T helper (Th) cell-related signals, and pronounced abilities to promote interleukin (IL)-12p70 production in DCs and the development of Th1 responses. This helper pathway of NK cell differentiation, which is not associated with any enhancement of cytolytic activity, is induced by IL-18, but not other NK cell-activating factors. It is blocked by prostaglandin (PG)E2, a factor that induces a similar CD83+/CCR7+/CD25+ LN-homing phenotype in maturing DCs. The current data demonstrate independent regulation of the "helper" versus "effector" pathways of NK cell differentiation and novel mechanisms of immunoregulation by IL-18 and PGE2.

Defining the critical hurdles in cancer immunotherapy.

Scientific discoveries that provide strong evidence of antitumor effects in preclinical models often encounter significant delays before being tested in patients with cancer. While some of these delays have a scientific basis, others do not. We need to do better. Innovative strategies need to move into early stage clinical trials as quickly as it is safe, and if successful, these therapies should efficiently obtain regulatory approval and widespread clinical application. In late 2009 and 2010 the Society for Immunotherapy of Cancer (SITC), convened an "Immunotherapy Summit" with representatives from immunotherapy organizations representing Europe, Japan, China and North America to discuss collaborations to improve development and delivery of cancer immunotherapy. One of the concepts raised by SITC and defined as critical by all parties was the need to identify hurdles that impede effective translation of cancer immunotherapy. With consensus on these hurdles, international working groups could be developed to make recommendations vetted by the participating organizations. These recommendations could then be considered by regulatory bodies, governmental and private funding agencies, pharmaceutical companies and academic institutions to facilitate changes necessary to accelerate clinical translation of novel immune-based cancer therapies. The critical hurdles identified by representatives of the collaborating organizations, now organized as the World Immunotherapy Council, are presented and discussed in this report. Some of the identified hurdles impede all investigators; others hinder investigators only in certain regions or institutions or are more relevant to specific types of immunotherapy or first-in-humans studies. Each of these hurdles can significantly delay clinical translation of promising advances in immunotherapy yet if overcome, have the potential to improve outcomes of patients with cancer.

Interleukin-2 administration alters the CD4+FOXP3+ T-cell pool and tumor trafficking in patients with ovarian carcinoma.

Interleukin (IL)-2 is used in the immunotherapy of patients with certain cancer and HIV infection. IL-2 treatment reliably results in 16% to 20% objective clinical response rate in cancer patients, with significant durability of responses in selected patients. However, the mechanisms of therapeutic activity in responding versus nonresponding patients remain poorly understood. CD4(+)CD25(+)FOXP3(+) regulatory T (Treg) cells contribute to immunosuppressive networks in human tumors. We treated 31 ovarian cancer patients with IL-2. We show that administration of IL-2 induces the proliferation of existent Treg cells in patients with ovarian cancer. The potency of Treg cell proliferation is negatively determined by the initial prevalence of Treg cells, suggesting that Treg cells are a factor for self-controlling Treg cell proliferation. After IL-2 cessation, the number of Treg cells more efficiently dropped in clinical responders than nonresponders. Furthermore, IL-2 treatment stimulates chemokine receptor CXCR4 expression on Treg cells, enables Treg cell migration toward chemokine CXCL12 in the tumor microenvironment, and may enforce Treg cell tumor accumulation. Our findings support the concept that administration of IL-2 numerically and functionally affects the Treg cell compartment. These data provide an important insight in evaluating the clinical benefit and therapeutic prediction of IL-2 treatment in patients with cancer.

Cancer chemoprevention and cancer preventive vaccines--a call to action: leaders of diverse stakeholder groups present strategies for overcoming multiple barriers to meet an urgent need.

The emerging field of cancer prevention through chemoprevention agents and cancer vaccines offers significant promise for reducing suffering and death from cancer. However, that promise may not be kept unless major barriers to progress are lowered or eliminated. Among the most significant barriers are the relatively small investment from government and industry in research and development of cancer preventive agents; a predominant emphasis of translational cancer research on therapeutic interventions for metastatic or advanced cancer; complexities of prevention trial design; a relatively uncharted Food and Drug Administration (FDA) approval process for preventive agents; insufficient public and patient understanding of the importance and potential for cancer preventive measures, with consequent unpredictable public and patient willingness to take preventive agents; an uncertain reimbursement from payors; and limitations in patent law, liability protection, and data package exclusivity that undermine the opportunity for recouping investment. Viewed individually or collectively, each of these barriers serves as a substantial deterrent to intellectual and financial investment by all sectors of the cancer community. In an effort to ultimately overcome these barriers, a Cancer Prevention Research Summit was assembled June 12-13, 2006 in Bethesda, Maryland, organized by C-Change with support from the AACR. The Summit brought together some 120 leaders from private, public, and not-for-profit entities, including cancer researchers and clinicians; federal health officials; regulatory agency representatives; pharmaceutical, biotech, and food industry leaders; patent attorneys; economists; public and private provider group executives; and advocates. Participants engaged in a detailed process to more carefully define the major barriers, identify potential solutions, and formulate initial priorities and recommendations for action. At the conclusion of this dialogue among experts, the following recommended actions were outlined: define policy solutions to patent, intellectual property, and liability law barriers; create an advisory document about the approval process for cancer chemopreventive agents and vaccines for the FDA; develop new design models for cancer chemopreventive clinical trials; outline the business case for chemopreventive agents and vaccines for federal research agencies, payors and investors; and implement a communications strategy to increase public awareness about the importance of chemoprevention and cancer preventive vaccines.

The need to develop centers for environmental oncology.

The scale and scope of the cancer problem in the United States today is much greater than four decades ago when the formal war against the disease was first announced. Patterns of the disease are not fully explained by known risk factors. Much progress has been made in understanding the molecular basis of carcinogenesis, particularly the near consensus (realization) that virtually all cancers arise from an accumulation of genetic mutations and the more recent recognition of the role of inflammation and the tissue microenvironment, in particular for hormone-dependent cancers. However, most genetic mutations that contribute to cancer are not inherited, and thus must be attributable to accumulation of somatic mutations and epigenetic changes, from as yet poorly understood environmental factors, that certainly cannot be explained entirely by tobacco, use and arise over the course of a lifetime. Much of the national effort to control cancer has focused on detecting and treating the disease--not on seeking approaches to prevent cases from arising. Given this reality, we present a cross-disciplinary framework for establishing comprehensive research and policy centers focused on environmental oncology to be based at selected academic cancer centers across the country. The principal goal of such centers is to improve the ability to prevent cancer, by developing effective interventions based on insights obtained from epidemiology, including molecular epidemiology and basic scientific research on genomic, metabolomic, and other biomarkers of exposure, susceptibility, and disease. As the needed scientific evidence for environmental factors contributing to cancer is revealed, these academic centers will develop specific interventions and/or policy recommendations regarding ways to lower the burden of cancer, based on existing information about cancer hazards in the personal, occupational, and general environment. Ultimately the centers will improve the ability to identify and control the underlying causes of the occurrence of cancer and its progression.

Multiplexed immunobead-based cytokine profiling for early detection of ovarian cancer.

Early detection of ovarian cancer might improve clinical outcome. Some studies have shown the role of cytokines as a new group of tumor markers for ovarian cancer. We hypothesized that a panel comprised of multiple cytokines, which individually may not show strong correlation with the disease, might provide higher diagnostic power. To evaluate the diagnostic utility of cytokine panel, we used a novel multianalyte LabMAP profiling technology that allows simultaneous measurement of multiple markers. Concentrations of 24 cytokines (cytokines/chemokines, growth, and angiogenic factors) in combination with cancer antigen-125 (CA-125), were measured in sera of 44 patients with early-stage ovarian cancer, 45 healthy women, and 37 patients with benign pelvic tumors. Six markers, i.e., interleukin (IL)-6, IL-8, epidermal growth factor (EGF), vascular endothelial growth factor (VEGF), monocyte chemoattractant protein-1 (MCP-1), and CA-125, showed significant differences in serum concentrations between ovarian cancer and control groups. Out of this group, IL-6, IL-8, VEGF, EGF, and CA-125, were used in a classification tree analysis that resulted in 84% sensitivity at 95% specificity. The receiver operator characteristic curve created using the combination of markers produced sensitivities between 90% and 100% in the area of 80% to 90% specificity, whereas the receiver operator characteristic curve for CA-125 alone resulted in sensitivities of 70% to 80%. The classification tree analysis for discrimination of benign condition from ovarian cancer used CA-125, granulocyte colony-stimulating factor (G-CSF), IL-6, EGF, and VEGF resulting in 86.5% sensitivity and 93.0% specificity. The presented data show that simultaneous testing of a panel of serum cytokines and CA-125 using LabMAP technology may present a promising approach for ovarian cancer detection.

Allelic polymorphisms in the FcgammaRIIC gene can influence its function on normal human natural killer cells.

Natural killer (NK) cells are important in host defense against viruses and tumors and can induce death of virally infected cells following engagement of cell surface receptors. Human NK cells express receptors for the Fc portion of IgG which stimulate antibody-dependent cell-mediated cytotoxicity and induce cytokine production. We have shown that NK cells from certain individuals can express, in addition to CD16 (FcgammaRIIIa), isoforms of CD32 (FcgammaRIIc1-4). Expression of CD32 on NK cells is dependent on an allelic polymorphism of the FcgammaRIIC gene. We analyzed the expression and function of CD32 on NK cells from 31 normal donors. Fourteen of the 31 (45%) donors expressed CD32 on their NK cells. Molecular characterization of FcgammaRIIc isoforms expressed by the CD32+ donors revealed that the majority of donors expressed the FcgammaRIIc1 isoform. Interestingly, 3 of the 14 positive donors did not express FcgammaRIIc1, and we identified a novel isoform, FcgammaRIIc5, expressed by these individuals. The expression of this isoform was correlated to a second allelic polymorphism that controls exon splicing. One of the three was found to express FcgammaRIIb on the NK cells. Biochemical analysis revealed that CD32+ donors of both types expressed a 40-kDa protein, specifically immunoprecipitated by anti-CD32 monoclonal antibodies. Functionally, only individuals expressing the FcgammaRIIc1 isoform were able to trigger reverse antibody-dependent cell-mediated cytotoxicity via CD32 whereas a CD32+ individual expressing the FcgammaRIIb isoform was unable to trigger this function. These results demonstrate that the presence of multiple allelic polymorphisms in the FcgammaRIIC gene determine the expression and function of CD32 on NK cells.

A novel epitope of N-CAM defines precursors of human adherent NK cells.

Activated, adherent natural killer (A-NK) cells represent a distinct subpopulation of interleukin (IL)-2-stimulated NK cells, which are selectively endowed with the increased expression of integrins and ability to adhere to solid surfaces, migrate into, infiltrate, and destroy cancerous tissues. The present study defines the phenotype and functions of precursors of A-NK (pre-A-NK) cells in humans. Peripheral blood pre-A-NK cells, in contrast to the rest of NK cells, express a novel epitope of CD56 neuronal cell adhesion molecule, termed ANK-1, and increased cell-surface levels of integrins. Pre-A-NK cells also express low levels of CD56 and CD161, and some express CD162 receptor, do not express CD25 or activation markers, and are effective mediators of NK cytotoxicity. Thus, pre-A-NK cells are generally similar to CD56(dim) NK cells. However, pre-A-NK cells differ from the main NK cell subpopulation by having a lower expression level of CD16 and a lower ability to mediate redirected antibody-dependent, cell-mediated cytotoxicity. More importantly, pre-A-NK cells are preferentially endowed with the ability to rapidly respond to IL-2 by integrin-mediated adherence to endothelial cells, extracellular matrix, and plastic. This early, specific response of pre-A-NK cells to IL-2 is followed by their activation, vigorous proliferation, and differentiation into phenotypically and functionally similar A-NK cells. Pre-A-NK cells represent only approximately 26% of peripheral blood NK cells but encompass the majority of NK cells in normal and cancerous, solid tissues. We conclude that pre-A-NK cells represent a distinct subset of resting, mature NK cells with the characteristics indicative of their ability to migrate and reside in solid tissues.

The FDA guidance on therapeutic cancer vaccines: the need for revision to include preventive cancer vaccines or for a new guidance dedicated to them.

Cancer vaccines based on antigens derived from self molecules rather than pathogens have been under basic and clinical investigations for many years. Up until very recently, they had been tested primarily in the setting of metastatic disease with the goal to engage the immune system in slowing down disease progression. Many therapeutic vaccine trials, either investigator initiated or led by pharmaceutical companies, have been completed and many are currently ongoing, following the FDA Guidance on therapeutic cancer vaccines published in 2011. In recent years, the target of cancer vaccines is being shifted to early cancer and even premalignant disease with the goal of preventing cancer. Although some issues addressed in the FDA Guidance on therapeutic vaccines apply to preventive vaccines, many do not. Here, we discuss a set of recommendations for revising the current Guidance to also cover preventive vaccines, or to include in a new Guidance dedicated specifically to vaccines for cancer prevention.

Cancer immunotherapy with natural killer cells.

Natural killer (NK) cells were first identified for their ability to kill tumor cells of different origins. They were subsequently found to be able to kill some normal cells, especially those infected by certain viruses. Natural killer cells are a distinct lymphocytic population, with the morphology of large granular lymphocytes, and they lack surface Ig or T-cell markers. Natural killer cytotoxicity is enhanced in vitro in the presence of cytokines such as interleukin-2 and interferon-alpha. However, when used in immunotherapy, these cytokines have not consistently augmented NK activity or shown antitumor effects. One explanation for this divergence is that NK cell activity is suppressed in tumor tissues by various factors, including reactive oxygen species produced by infiltrating monocytes and macrophages. Agents that inhibit the generation of reactive oxygen species, such as histamine, may abrogate the suppression exerted on NK cells by monocytes/macrophages, therefore offering potential therapeutic benefit as immunoadjuvants.

Local administration of IL-12-transfected dendritic cells induces antitumor immune responses to colon adenocarcinoma in the liver in mice.

Colorectal cancer is one of the most common fatal malignancies in the United States, with an incidence second only to lung cancer. The liver is the most common site of colorectal metastases and frequently the only affected organ once the primary tumor has been surgically removed. The only potentially curative treatment for metastatic colorectal cancer in the liver is surgery, although most patients are not eligible for resection. We have therefore, evaluated the therapeutic efficacy of dendritic cells (DCs) engineered to express IL-12 in a liver metastasis model. Direct administration of DCs into the portal vein significantly inhibited the growth of established MC38 colon carcinoma in the liver in C57BL/6 mice. This effect was accompanied by an intratumoral accumulation of CD4+, CD8+, and NLDC-145+ immune effector cells, and also resulted in a systemic immune response as determined by enhanced production of IFN-gamma by T lymphocytes isolated from both spleen and draining lymph nodes. Evaluation of homing of Cy3-labeled DCs following the portal vein injection confirmed their distribution in the liver and lymphoid tissue. Thus, a local delivery of DCs transduced with the IL-12 gene can not only inhibit colorectal tumor growth in vivo but also mount systemic antitumor immune responses. This approach is likely to improve the outcome of immunotherapy for metastatic colorectal cancer since high numbers of tumor-associated DCs positively correlate with a more favorable prognosis. Simultaneous local gene therapy with IL-12 will further improve clinical efficacy without placing the patient at risk for systemic toxicity.

Cancer immunotherapy with interleukin-2-activated natural killer cells.

Natural killer (NK) cells are a subset of lymphocytes with a distinct morphologic appearance (large granular lymphocytes [LGL]) and the ability to kill virally infected and tumor targets but to spare most normal cells. NK cells respond to a variety of biologic agents, such as interleukin-2 (IL-2), or interferons, by upregulation of cytolytic, secretory, and proliferative functions. In cancer-bearing hosts, NK cells have been considered to be the major component of antitumor immunity responsible for rapid elimination of malignant cells from the blood. More recently, however, studies have demonstrated the ability of adoptively transferred, IL-2-activated NK cells to selectively localize into solid tumors tissue and to eliminate established tumors. While these findings indicate a role for NK cells in cancer immunotherapy, additional studies are needed in both animal models and in humans to optimize clinical protocols of cancer therapy based on these cells.

Therapeutic in situ autovaccination against solid cancers with intratumoral poly-ICLC: case report, hypothesis, and clinical trial.

Pathogen-associated molecular patterns (PAMP) are stand-alone innate and adaptive immunomodulators and critical vaccine components. We present a strategy of sequential intratumoral (i.t.) and intramuscular (i.m.) injections of the stabilized dsRNA viral mimic and PAMP, polyinosinic-polycytidylic acid-polylysine-carboxymethylcellulose (poly-ICLC, Hiltonol; Oncovir). We report the first treated patient, a young man with an exceptionally advanced facial embryonal rhabdomyosarcoma with extension to the brain. After treatment, the patient showed tumor inflammation consistent with immunotherapy, followed by gradual, marked tumor regression, with extended survival. Sequential i.t. and i.m. poly-ICLC injections mimicking a viral infection can induce an effective, in situ, personalized systemic therapeutic "autovaccination" against tumor antigens of a patient. We postulate a three-step immunomodulatory process: (i) innate-immune local tumor killing induced by i.t. poly-ICLC; (ii) activation of dendritic cells with Th1 cell- and CTL-weighted priming against the released tumor antigens; and (iii) i.m. poly-ICLC maintenance of the systemic antitumor immune response via chemokine induction, facilitation of CTL killing through the induction of costimulators such as OX40, inflammasome activation, and increase in the T-effector/Treg ratio. These results support the use of certain simple and inexpensive i.t. PAMPs to favorably stimulate effective immunity against solid cancers. A phase II clinical trial testing the hypothesis presented has begun accrual (clinicaltrials.gov, NCT01984892).

Immunotherapy of cancer via mediation of cytotoxic T lymphocytes by methionine enkephalin (MENK).

The aim of this study was to investigate the immunological mechanisms by which synthetic methionine enkephalin (MENK) exerts therapeutic effects on tumor growth. Our findings in vivo or in vitro show that MENK treatment either in vivo or in vitro could up-regulate the percentages of CD8+T cells, induce markers of activated T cells, increased cytotoxic activity against mouse S180 tumor cells and increase secretion of IFNγ. In addition, the adoptively transferred CD8+T cells, after either in vitro or in vivo treatment with MENK, result in significantly increased survival of S180 tumor-bearing mice and significant shrinkage in tumor growth. Opioid receptors are detected on normal CD8+T cells and exposure to MENK leads to increased expression of opioid receptors. Interaction between MENK and the opioid receptors on CD8+T cells appears to be essential for the activation of CTL, since the addition of naltrexone (NTX), an opioid receptor antagonist, significantly inhibits all of the effects of MENK. The evidence obtained indicates that the MENK-induced T cell signaling is associated with a significant up-regulation of Ca2+ influx into the cytoplasm and the translocation of NFAT2 into nucleus, and these signaling effects are also inhibited by naltrexone.

Regulatory approval of cancer risk-reducing (chemopreventive) drugs: moving what we have learned into the clinic.

This article endeavors to clarify the current requirements and status of regulatory approval for chemoprevention (risk reduction) drugs and discusses possible improvements to the regulatory pathway for chemoprevention. Covering a wide range of topics in as much depth as space allows, this report is written in a style to facilitate the understanding of nonscientists and to serve as a framework for informing the directions of experts engaged more deeply with this issue. Key topics we cover here are as follows: a history of definitive cancer chemoprevention trials and their influence on the evolution of regulatory assessments; a brief review of the long-standing success of pharmacologic risk reduction of cardiovascular diseases and its relevance to approval for cancer risk reduction drugs; the use and limitations of biomarkers for developing and the approval of cancer risk reduction drugs; the identification of individuals at a high(er) risk for cancer and who are appropriate candidates for risk reduction drugs; business models that should incentivize pharmaceutical industry investment in cancer risk reduction; a summary of scientific and institutional barriers to development of cancer risk reduction drugs; and a summary of major recommendations that should help facilitate the pathway to regulatory approval for pharmacologic cancer risk reduction drugs.

Elimination of human lung cancer stem cells through targeting of the stem cell factor-c-kit autocrine signaling loop.

Cancer stem cells (CSC) are thought to be responsible for tumor initiation and tumor regeneration after chemotherapy. Previously, we showed that chemotherapy of non-small cell lung cancer (NSCLC) cells lines can select for outgrowth of highly tumorigenic and metastatic CSCs. The high malignancy of lung CSCs was associated with an efficient cytokine network. In this study, we provide evidence that blocking stem cell factor (SCF)-c-kit signaling is sufficient to inhibit CSC proliferation and survival promoted by chemotherapy. CSCs were isolated from NSCLC cell lines as tumor spheres under CSC-selective conditions and their stem properties were confirmed. In contrast to other tumor cells, CSCs expressed c-kit receptors and produced SCF. Proliferation of CSCs was inhibited by SCF-neutralizing antibodies or by imatinib (Gleevec), an inhibitor of c-kit. Although cisplatin treatment eliminated the majority of tumor cells, it did not eliminate CSCs, whereas imatinib or anti-SCF antibody destroyed CSCs. Significantly, combining cisplatin with imatinib or anti-SCF antibody prevented the growth of both tumor cell subpopulations. Our findings reveal an important role for the SCF-c-kit signaling axis in self-renewal and proliferation of lung CSCs, and they suggest that SCF-c-kit signaling blockade could improve the antitumor efficacy of chemotherapy of human NSCLC.

Biological significance of prolactin in gynecologic cancers.

There is increasing evidence that prolactin (PRL), a hormone/cytokine, plays a role in breast, prostate, and colorectal cancers via local production or accumulation. Elevated levels of serum PRL in ovarian and endometrial cancers have been reported, indicating a potential role for PRL in endometrial and ovarian carcinogenesis. In this study, we show that serum PRL levels are significantly elevated in women with a strong family history of ovarian cancer. We show dramatically increased expression of PRL receptor in ovarian and endometrial tumors as well as in endometrial hyperplasia, signifying the importance of PRL signaling in malignant and premalignant conditions. PRL mRNA was expressed in ovarian and endometrial tumors, indicating the presence of an autocrine loop. PRL potently induced proliferation in several ovarian and endometrial cancer cell lines. Binding of PRL to its receptor was followed by rapid phosphorylation of extracellular signal-regulated kinase (ERK) 1/2, mitogen-activated protein kinase/ERK kinase 1, signal transducer and activator of transcription 3, CREB, ATF-2, and p53 and activation of 37 transcription factors in ovarian and endometrial carcinoma cells. PRL also activated Ras oncogene in these cells. When human immortalized normal ovarian epithelial cells were chronically exposed to PRL, a malignant transformation occurred manifested by the acquired ability of transformed cells to form clones, grow in soft agar, and form tumors in severe combined immunodeficient-beige mice. Transformation efficiency was diminished by a Ras inhibitor, providing proof that PRL-induced transformation uses the Ras pathway. In summary, we present findings that indicate an important role for PRL in ovarian and endometrial tumorigenesis. PRL may represent a risk factor for ovarian and endometrial cancers.

Sheddase activity of tumor necrosis factor-alpha converting enzyme is increased and prognostically valuable in head and neck cancer.

Tumor necrosis factor alpha converting enzyme (TACE) is a sheddase overexpressed in cancers that generates cancer cell growth and survival factors, and is implicated in carcinogenesis and tumor growth. This indicates that TACE could be a potentially important cancer biomarker. Unexpectedly, TACE expression in cancer tissues does not correlate with cancer stage or invasiveness. Although TACE sheddase activity is a more direct and potentially better indicator of TACE biology and might be a better cancer biomarker than TACE expression, it has not been studied in cancer tissues. In the present study, we developed a reliable specific assay for quantification of TACE sheddase activity, investigated TACE activity and TACE protein expression in head and neck cancer (HNC) tissues, and examined the correlation of the results with HNC clinical stages and likelihood to recur. We found that HNC cell lines and tissues contained remarkably higher quantities of TACE activity and TACE protein than normal keratinocytes or oral mucosa. siRNA silencing of TACE resulted in the inhibition of release of the tumorogenic factors amphiregulin and transforming growth factor alpha, and tumor protective factors tumor necrosis factor receptors from HNC cells. Importantly, TACE activity, but not TACE protein expression, was significantly higher in large, T3/T4, primary tumors relative to small, T1/T2, primary tumors, and especially in primary tumors likely to recur relative to those unlikely to recur. These data show that increased TACE activity in cancer is biologically and clinically relevant, and indicate that TACE activity could be a significant biomarker of cancer prognosis.