Kinetics of development and characteristics of antibodies induced in cancer patients against yeast expressed rDNA derived granulocyte macrophage colony stimulating factor (GM-CSF)

We have determined the presence and kinetics of granulocyte macrophage colony stimulating factor (GM-CSF) antibodies induced after repeated administration of a yeast expressed GM-CSF product in prostate cancer patients with minimal recurrent disease using a panel of assays for detection and characterization of antibodies. Results showed that all 15 prostate cancer patients treated with GM-CSF developed GM-CSF reactive antibodies during the course of therapy. Most patients (87%) developed GM-CSF reactive antibodies within 3 months while in other patients (13%), these antibodies were induced after additional cycles of GM-CSF treatment. For most patients, the timing of occurrence of these antibodies was the same regardless of whether the ELISA or surface plasmon resonance (SPR) assays were used for detection. However, in two patients, the recognition of GM-CSF reactive antibodies by SPR assays preceded their detection by ELISA. A significant number of patients (n=9, 60%) developed GM-CSF antibodies which neutralized the biological activity of GM-CSF in vitro in a cell-line based bioassay. These antibodies also recognized GM-CSF protein from different expression systems including the non-glycosylated protein from E. coli indicating that the antibody response is directed towards the amino acid backbone of the protein. A significant effect of GM-CSF antibodies on PSA modulation was not observed in this small cohort of patients despite an alteration in PSA levels in some treated patients. The study design used here did not allow conclusions regarding the relationship between neutralizing antibodies and the PSA levels which were used as a marker for clinical outcome. Implementation of a clinical strategy which permits monitoring for antibody development and for levels of a relevant pre-determined clinical marker at appropriate time-points is necessary for assessing the impact of antibody development on the therapeutic efficacy of the protein.

Transgenic crops : new weed problems for Canada?

Over 25 000 transgenic field trials were conducted globally from 1986-1997, and many transgenic crops, including soybean (Glycine max), maize (Zea mays), tobacco (Nicotiana tabaccum), cotton (Gossypium hirsutum), canola (Brassica napus, B. rapa), tomato (Lycopersicon esculentum) and potato (Solarium tuberosum) have been commercially released. There has been a high adoption rate, with at least 28 million ha reported for 1998, with herbicide- and insect-resistant plants occupying 71 and 28% of the releases, respectively. The current status of commercial production of transgenic crops in Canada is summarized. Transgenic crops have the potential to change weed communities/populations in three principal ways, via: 1 ) escape and proliferation of the transgenic plants as 'weedy' volunteers with subsequent displacement of the crop, weed and/or natural vegetation; 2) hybridization with and transgene infiltration into related weedy and/or wild species, resulting in invigorated weeds and/or alteration of natural gene frequencies in these species; and 3) genetic changes in populations of unrelated species, as a result of changes to the environment, in particular herbicide-resistant (HR) transgenic crops and the development of HR weeds. Potential risk can be estimated a priori using knowledge of the systematics of crop/wild/weed complexes. Risk must be assessed on a case-by-case basis for each crop, each country/ecological region, and for each trait. Potential weed risks will be greater if crop volunteers are predisposed to becoming weedy, are well adapted to the Canadian climate and if sexually compatible wild species are present.

Immunogenicity of GM-CSF products in cancer patients following immunostimulatory therapy with GM-CSF

There is a high risk of developing neutralising and non-neutralising antibodies when GM-CSF is used as an immunomodulatory agent in non-immunocompromised patients. The presence of neutralising antibodies may seriously hamper the clinical response of the patients. This must be taken into account when designing protocols if the biological activity of the exogenously administered GM-CSF is not to be impaired and the endogenous production of GM-CSF is not to be inactivated. Assessment of production of neutralising antibodies during cytokine therapy is important for predicting the clinical response to progressive therapy. Use of validated assays is imperative for evaluation of antibodies generated following therapy with a particular protein.

The new bisphosphonate, Zometa (zoledronic acid), decreases skeletal complications in both osteolytic and osteoblastic lesions: a comparison to pamidronate

Bisphosphonates are the treatment of choice for lytic bone lesions associated with breast cancer. In contrast, bone lesions associated with prostate cancer are predominately osteoblastic. Zoledonic acid (Zol) is a new-generation bisphosphonate that is approximately 2-3 orders of magnitude more potent than pamidronate (Pam) in preclinical models and has demonstrated clinical efficacy in patients with both lytic and blastic lesions. Zoledonic acid (4 mg via 15 min infusion) every 3-4 weeks was directly compared to Pam (90 mg via 2 hr infusion) in 767 patients with breast cancer and bone metastases. The primary endpoint was the proportion of patients experiencing a skeletal-related event (SRE) over 13 months. Zoledonic acid was as effective as Pam, and the proportion of Zol-treated patients with an SRE (42% in the hormonal therapy strata and 44% in the chemotherapy strata) was comparable to the original studies comparing Pam to placebo. Among 371 breast cancer patients receiving hormonal therapy, the proportion of patients with an SRE was 47% for Pam vs. 57% for placebo (P = 0.057), and among 380 patients treated with chemotherapy, the proportions with an SRE were 43% for Pam vs. 56% for placebo (P = 0.008) at 12 months. Zoledronic acid (4 mg) has been compared to placebo in a randomized Phase III trial involving 422 men with hormone-refractory prostate cancer metastatic to bone. Zoledonic acid demonstrated a significant advantage over placebo for median time to first SRE (median not reached for Zol vs. 321 days for placebo; P = 0.011), the proportion of patients with an SRE over 15 months (33 vs. 44% for placebo; P = 0.021), and mean skeletal morbidity rate (number of SREs/time, 0.08 vs. 1.49 for placebo; P = 0.006). In addition, the effects of Zol were apparent early. At 3 months, only 12% of Zol-treated patients had an SRE vs. 23% for placebo (P = 0.003), and at 6 months, the proportions were 21 vs. 31% for placebo (P = 0.025). In contrast, a previous study of Pam in 236 prostate cancer patients found that Pam was no more effective than placebo in reducing bone pain or SREs over 6 months. In these studies, Zol was well tolerated with a safety profile similar to other IV bisphosphonates. In conclusion, Zol is the first bisphosphonate to demonstrate efficacy in both lytic and blastic disease. The unique properties of this novel agent should be further explored in future clinical trials.

Dendritic cell-based treatment of cancer: closing in on a cellular therapy

PURPOSE

Dendritic cells are the most potent antigen-presenting cells and are critical to initiation of immune responses. Dendritic cells loaded ex vivo with tumor-associated antigen are being administered to cancer patients in an effort to jump-start a potent, cell-mediated anticancer immune response resulting in tumor shrinkage and clinical benefit.

PATIENTS AND METHODS

Dendreon Corporation has designed three therapeutic vaccines using blood-derived dendritic cells loaded ex vivo with antigen: Provenge for prostate cancer; Mylovenge for multiple myeloma and other B-cell malignancies; and APC8024 for cancers expressing the HER-2/neu proto-oncogene.

RESULTS

Preclinical studies demonstrated that blood dendritic cells matured spontaneously in short-term culture without growth factors, and that fusion of antigens with granulocyte-macrophage colony-stimulating factor enhances antigen uptake and presentation by blood dendritic cells. Phase I/II trials suggest that these dendritic cell-based vaccines are safe and well tolerated. Provenge has demonstrated antitumor activity in hormone-refractory prostate cancer; approximately 20% of patients experienced decreased prostate-specific antigen (i.e., PSA) levels and a similar percentage experienced disease stabilization. Double-blind, placebo-controlled, randomized trials in metastatic, asymptomatic hormone-refractory prostate cancer have been initiated. Phase II data on Mylovenge are similarly encouraging, and expanded phase II testing is ongoing in anticipation of opening phase III trials in 2002. APC8024 is in early clinical development and has shown significant capacity to elicit antigen-specific immune responses.

CONCLUSION

Antigen delivery by ex vivo antigen-loaded dendritic cells may be an effective approach to cancer immunotherapy.

Creatine use among young athletes

OBJECTIVE

Creatine is a nutritional supplement that is purported to be a safe ergogenic aid in adults. Although as many as 28% of collegiate athletes admit taking creatine, there is little information about creatine use or potential health risk in children and adolescents. Although the use of creatine is not recommended in people less than 18 years of age, numerous anecdotal reports indicate widespread use in young athletes. The purpose of this study was to determine the frequency, risk factors, and demographics of creatine use among middle and high school student athletes.

METHODS

Before their annual sports preparticipation physical examinations, middle and high school athletes aged 10 to 18 in Westchester County, a suburb north of New York City, were surveyed in a confidential manner. Information was collected regarding school grade, gender, specific sport participation, and creatine use.

RESULTS

Overall, 62 of 1103 participants (5.6%) admitted taking creatine. Creatine use was reported in every grade, from 6 to 12. Forty-four percent of grade 12 athletes surveyed reported using creatine. Creatine use was significantly more common (P <.001) among boys (53/604, 8.8%) than girls (9/492, 1.8%). Although creatine was taken by participants in every sport, use was significantly more common among football players, wrestlers, hockey players, gymnasts, and lacrosse players (P <.001 for all). The most common reasons cited for taking creatine were enhanced performance (74.2% of users) and improved appearance (61.3%), and the most common reason cited for not taking creatine was safety (45.7% of nonusers).

CONCLUSIONS

Despite current recommendations against use in adolescents less than 18 years old, creatine is being used by middle and high school athletes at all grade levels. The prevalence in grades 11 and 12 approaches levels reported among collegiate athletes. Until the safety of creatine can be established in adolescents, the use of this product should be discouraged.

Activation of cardiac gene expression by myocardin, a transcriptional cofactor for serum response factor

Serum response factor (SRF) regulates transcription of numerous muscle and growth factor-inducible genes. Because SRF is not muscle specific, it has been postulated to activate muscle genes by recruiting myogenic accessory factors. Using a bioinformatics-based screen for unknown cardiac-specific genes, we identified a novel and highly potent transcription factor, named myocardin, that is expressed in cardiac and smooth muscle cells. Myocardin belongs to the SAP domain family of nuclear proteins and activates cardiac muscle promoters by associating with SRF. Expression of a dominant negative mutant of myocardin in Xenopus embryos interferes with myocardial cell differentiation. Myocardin is the founding member of a class of muscle transcription factors and provides a mechanism whereby SRF can convey myogenic activity to cardiac muscle genes.

Strength training by children and adolescents

Pediatricians are often asked to give advice on the safety and efficacy of strength training programs for children and adolescents. This review, a revision of a previous American Academy of Pediatrics policy statement, defines relevant terminology and provides current information on risks and benefits of strength training for children and adolescents.

Organized sports for children and preadolescents

Participation in organized sports provides an opportunity for young people to increase their physical activity and develop physical and social skills. However, when the demands and expectations of organized sports exceed the maturation and readiness of the participant, the positive aspects of participation can be negated. The nature of parental or adult involvement can also influence the degree to which participation in organized sports is a positive experience for preadolescents. This updates a previous policy statement on athletics for preadolescents and incorporates guidelines for sports participation for preschool children. Recommendations are offered on how pediatricians can help determine a child's readiness to participate, how risks can be minimized, and how child-oriented goals can be maximized.

Focal therapy for prostate cancer 1996: maximizing outcome

OBJECTIVES

To summarize improvements in patient selection and the results of focal therapy for the management of localized prostate cancer.

METHODS

A contemporary series of patients managed with wide surgical excision, radiation therapy (three-dimensional conformal radiation, interstitial radiation, and charged-particle or proton therapy), and cryo-therapy were reviewed.

RESULTS

We used preoperative cancer grade, transrectal ultrasound, and serum prostate-specific antigen (PSA) in all patients, and cross-sectional imaging and bone scans in selected patients to allow for reasonably accurate cancer staging and selection of patients most likely to be cured by radical prostatectomy or radiation. In patients with extracapsular extension of prostate cancer, wide surgical excision and achievement of a clear surgical margin had therapeutic value. Newer radiation techniques resulted in a higher likelihood of prostate cancer control than previous techniques. Cryotherapy for patients with stages T1 through 3 prostate cancer was associated with a posttreatment undetectable PSA rate of 48% and a positive biopsy rate of 23%.

CONCLUSIONS

Patients with organ-confined and, therefore, curable prostate cancer can be identified. Well-performed radical prostatectomy, radiation, and cryotherapy are alternative treatments for the management of localized prostate cancer.

The young athlete with chronic disease

Iron deficiency anemia can affect athletic performance. Physicians must be wary of the at risk population, namely vegetarians, female adolescents, and long distance athletes. Particular attention must be paid to nutritional intake and to the use of nonsteroidal anti-inflammatory agents and aspirin.

Valuing the unseen emotional labour of nursing

This paper argues that comforting, listening, being reassuring and showing sympathy are important nursing skills that are vital to a patients' well-being and, as such, should be both valued and remunerated. The author also argues that the invisibility of these skills has been compounded by the NHS and Community Care Act 1990. This has meant that long-term care is being transferred into the hands of the private and voluntary sectors and informal carers. As an alternative to residential care, many social services departments now use the home care services of not-for-profit care agencies who employ 'ordinary' people to enable those needing long-term care to remain in their own home. Such workers are often paid in a way that does not remunerate the emotional element of their labour.