ANALYSIS OF THE CORYNEBACTERIUM PARVUM-INDUCED DECLINE OF MURINE NATURAL KILLER CELL-MEDIATED CYTOTOXICITY

Treatment of mice with the immunomodulating agent, Corynebacterium parvum (C. parvum), was shown to result in a severe and long-lasting depression of splenic natural killer (NK) cell-mediated cytotoxicity 5-21 days post-inoculation. Because NK cells have been implicated in immunosurveillance against malignancy (due to their spontaneous occurrence and rapid reactivity to a variety of histological types of tumors), as well as in resistance to established tumors, this decreased activity was of particular concern, since this effect is contrary to that which would be considered therapeutically desirable in cancer treatment (i.e. a potentiation of antitumor effector functions, including NK cell activity, would be expected to lead to a more effective destruction of malignant cells). Therefore, an analysis of the mechanism of this decline of splenic NK cell activity in C.parvum treated mice was undertaken.^ From in vitro co-culturing experiments, it was found that low NK-responsive C. parvum splenocytes were capable of reducing the normally high-reactivity of cells from untreated syngeneic mice to YAC-1 lymphoma, suggesting the presence of NK-directed suppressor cells in C. parvum treated animals. This was further supported by the demonstration of normal levels of cytotoxicity in C. parvum splenocyte preparations following Ficoll-Hypaque separation, which coincided with removal of the NK-suppressive capabilities of these cells. The T cell nature of these regulatory cells was indicated by (1) the failure of C. parvum to cause a reduction of NK cell activity, or the generation of NK-directed suppressor cells in T cell-deficient athymic mice, (2) the removal of C. parvum-induced suppression by T cell-depleting fractionation procedures or treatments, and (3) demonstration of suppression of NK cell activity by T cell-enriched C. parvum splenocytes. These studies suggest, therefore, that the eventual reduction of suppression by T cell elimination and/or inhibition, may result in a promotion of the antitumor effectiveness of C. parvum due to the contribution of "freed" NK effector cell activity.^ However, the temporary suppression of NK cell activity induced by C. parvum (reactivity of treated mice returns to normal levels within 28 days after C. parvum injection), may in fact be favorable in some situations, e.g. in bone marrow transplantation cases, since NK cells have been suggested to play a role also in the process of bone marrow graft rejection.^ Therefore, the discriminate use of agents such as C. parvum may allow for the controlled regulation of NK cell activity suggested to be necessary for the optimalization of therapeutic regimens. ^

An analysis of two methods for the classification of stage of readiness to obtain repeat mammography screening

Background and purpose: Breast cancer continues to be a health problem for women, representing 28 percent of all female cancers and remaining one of the leading causes of death for women. Breast cancer incidence rates become substantial before the age of 50. After menopause, breast cancer incidence rates continue to increase with age creating a long-lasting source of concern (Harris et al., 1992). Mammography, a technique for the detection of breast tumors in their nonpalpable stage when they are most curable, has taken on considerable importance as a public health measure. The lifetime risk of breast cancer is approximately 1 in 9 and occurs over many decades. Recommendations are that screening be periodic in order to detect cancer at early stages. These recommendations, largely, are not followed. Not only are most women not getting regular mammograms, but this circumstance is particularly the case among older women where regular mammography has been proven to reduce mortality by approximately 30 percent. The purpose of this project was to increase our understanding of factors that are associated with stage of readiness to obtain subsequent mammograms. A secondary purpose of this research was to suggest further conceptual considerations toward the extension of the Transtheoretical Model (TTM) of behavior change to repeat screening mammography. ^ Methods. A sample (n = 1,222) of women 50 years and older in a large multi-specialty clinic in Houston, Texas was surveyed by mail questionnaire regarding their previous screening experience and stage of readiness to obtain repeat screening. A computerized database, maintained on all women who undergo mammography at the clinic, was used to identify women who are eligible for the project. The major statistical technique employed to select the significant variables and to examine the man and interaction effects of independent variables on dependent variables was polychotomous stepwise, logistic regression. A prediction model for each stage of readiness definition was estimated. The expected probabilities for stage of readiness were calculated to assess the magnitude and direction of significant predictors. ^ Results. Analysis showed that both ways of defining stage of readiness for obtaining a screening mammogram were associated with specific constructs, including decisional balance and processes of the change. ^ Conclusions. The results of the present study demonstrate that the TTM appears to translate to repeat mammography screening. Findings in the current study also support finding of previous studies that suggest that stage of readiness is associated with respondent decisional balance and the processes of change. ^

Molecular mechanism of PUVA-induced apoptosis in mouse epidermal cells

A combination of psoralens and ultraviolet-A radiation referred to as PUVA, is widely used in the treatment of psoriasis. PUVA therapy is highly effective in killing hyperproliferative cells, but its mechanism of action has not been fully elucidated. Psoralen binds to DNA, and upon photoactivation by UVA, it forms monofunctional adducts and interstrand cross-links. PUVA treatment has been shown to be mutagenic and to produce tumors in animals. In addition, epidemiological studies have reported a 10 to 15 percent increased risk of developing squamous cell carcinoma in individuals treated chronically with PUVA. However, it remains a treatment for skin disorders such as psoriasis because its benefits outweigh its risks. The widespread use of PUVA therapy and its associated cancer risk requires us to understand the molecular mechanisms by which PUVA induces cell death. Immortalized JB6 mouse epidermal cells, p53−/− mice, and Fas Ligand−/− (gld) mice were used to investigate the molecular mechanism by which PUVA kills cells. Treatment of JB6 cells with 10 μg/ml 8-methoxypsoralen followed by irradiation with 20 kJ/m2 UVA resulted in cell death. The cells exhibited morphological and biochemical characteristics of apoptosis such as chromatin condensation, DNA ladder formation, and TUNEL-positivity. PUVA treatment stabilized and phosphorylated p53 leading to its activation, as measured by nuclear localization and induction of p21Waf/Cip1, a transcriptional target of p53. Subsequent in vivo studies revealed that there was statistically significantly less apoptosis in p53 −/− mice than in p53+/+ mice at 72 hours after PUVA. In addition, immunohistochemical analysis revealed more Fas and FasL expression in p53+/+ mice than in p53−/− mice, suggesting that p53 is required to transcriptionally activate Fas, which in turn causes the cells to undergo apoptosis. Studies with gld mice confirmed a role for Fas/FasL interactions in PUVA-induced apoptosis. There was statistically significantly less apoptosis in gld mice compared with wild-type mice 24, 48, and 72 hours after PUVA. These results demonstrate that PUVA-induced apoptosis in mouse epidermal cells requires p53 and Fas/FasL interactions. These findings may be important for designing effective treatments for diseases such as psoriasis without increasing the patient's risk for skin cancer. ^

Effects of congressional modernization laws on public access to innovative medical device technologies

The Federal Food and Drug Administration (FDA) and the Centers for Medicare and Medicaid (CMS) play key roles in making Class III, medical devices available to the public, and they are required by law to meet statutory deadlines for applications under review. Historically, both agencies have failed to meet their respective statutory requirements. Since these failures affect patient access and may adversely impact public health, Congress has enacted several “modernization” laws. However, the effectiveness of these modernization laws has not been adequately studied or established for Class III medical devices. ^ The aim of this research study was, therefore, to analyze how these modernization laws may have affected public access to medical devices. Two questions were addressed: (1) How have the FDA modernization laws affected the time to approval for medical device premarket approval applications (PMAs)? (2) How has the CMS modernization law affected the time to approval for national coverage decisions (NCDs)? The data for this research study were collected from publicly available databases for the period January 1, 1995, through December 31, 2008. These dates were selected to ensure that a sufficient period of time was captured to measure pre- and post-modernization effects on time to approval. All records containing original PMAs were obtained from the FDA database, and all records containing NCDs were obtained from the CMS database. Source documents, including FDA premarket approval letters and CMS national coverage decision memoranda, were reviewed to obtain additional data not found in the search results. Analyses were conducted to determine the effects of the pre- and post-modernization laws on time to approval. Secondary analyses of FDA subcategories were conducted to uncover any causal factors that might explain differences in time to approval and to compare with the primary trends. The primary analysis showed that the FDA modernization laws of 1997 and 2002 initially reduced PMA time to approval; after the 2002 modernization law, the time to approval began increasing and continued to increase through December 2008. The non-combined, subcategory approval trends were similar to the primary analysis trends. The combined, subcategory analysis showed no clear trends with the exception of non-implantable devices, for which time to approval trended down after 1997. The CMS modernization law of 2003 reduced NCD time to approval, a trend that continued through December 2008. This study also showed that approximately 86% of PMA devices do not receive NCDs. ^ As a result of this research study, recommendations are offered to help resolve statutory non-compliance and access issues, as follows: (1) Authorities should examine underlying causal factors for the observed trends; (2) Process improvements should be made to better coordinate FDA and CMS activities to include sharing data, reducing duplication, and establishing clear criteria for “safe and effective” and “reasonable and necessary”; (3) A common identifier should be established to allow tracking and trending of applications between FDA and CMS databases; (4) Statutory requirements may need to be revised; and (5) An investigation should be undertaken to determine why NCDs are not issued for the majority of PMAs. Any process improvements should be made without creating additional safety risks and adversely impacting public health. Finally, additional studies are needed to fully characterize and better understand the trends identified in this research study.^

Information sources influencing urban Mexican-American women's cancer screening participation

Breast and cervical cancer, though less common in Mexican-American than in Anglo women, are more likely to go undetected in Mexican-American women, leaving them more vulnerable to advanced disease and death. Although highly effective screening tests--the Pap smear and the mammogram--can detect these cancers early, many Mexican-American women do not regularly undergo these preventive screening tests.^ To explore the differential influence of encouraging sources of health information, this investigation examined the relationship between encouragement from a "peer"--husband or partner, child or children, other family members, or close friends--and a "health professional"--a doctor, a nurse, or another health professional--on Mexican-American women's cancer screening intentions and behaviors. Furthermore, this research explored whether the sources' influence on cancer screening intentions and behaviors differed depending on level of acculturation.^ One thousand seven hundred eleven surveys of Mexican-American women were analyzed to identify the source that most effectively encourages these women to participate in cancer screening. The data provided evidence that health professionals strongly influenced this population's cancer screening intentions and behaviors. Evidence for peer influence was also found; however, it was usually weaker, and, in some cases, negligible. Peer encouragement was related to Pap test behaviors and mammogram intentions, but not to Pap test intentions or mammogram behaviors. Consistently, women reported greater intentions and screening behaviors when encouraged from a health professional than from a peer. Acculturation was not found to be a modifying variable related to the relationship between sources of information and Pap test or mammogram intentions and behaviors.^ Because health professionals were identified as strongly influencing both intentions and behaviors for Pap tests and mammograms, further efforts should be undertaken to urge them to encourage their clients to obtain cancer screening. Failure to provide this encouragement leads to missed opportunities. Enlisting support from peers also may help to increase cancer screening participation in urban Mexican-American women; however, the consistently greater intentions and behaviors related to a health professional's encouragement indicated the greater power of the latter. ^