PRL-3: a phosphatase for metastasis?

The PRL-3 phosphatase has joined the cancer arena very recently but is rapidly gaining interest both as a putative prognostic factor and as a therapeutic target for metastatic tumors. In this issue Guo and colleagues provide another key piece of information by showing that the catalytic activity of PRL-3 is required for experimental metastasis formation in mouse models. Here we summarize the current knowledge and discuss what remains to be done before PRL-3 could be considered as a target for diagnostics or therapeutics in the clinical setting of human cancer.     

Targeting GSK-3: a promising approach for cancer therapy?

Glycogen synthase kinase (GSK)-3 has emerged as one of the most attractive therapeutic targets for the treatment of multiple neurological diseases, including Alzheimer's, stroke and bipolar disorders, as well as noninsulin-dependent diabetes mellitus and inflammation. Although the prominent role of GSK-3 in the adenomatous polyposis coli (APC)-beta-catenin destruction complex implies that inhibition of GSK-3 could possibly lead to tumor promotion through the activation of beta-catenin, several recent studies have shed new light on the activity of GSK-3 in cancer and provide insight into the molecular mechanisms by which it regulates tumor cell proliferation and survival of multiple human malignancies. In fact, GSK-3beta is a critical regulator of nuclear factor (NF)kappaB nuclear activity, suggesting that inhibition of GSK-3beta could be effective in the treatment of a wide variety of tumors with constitutively active NFkappaB. Herein, the authors will discuss the current understanding of the role of GSK-3 in human cancer and its potential as a therapeutic target.     

T3N0 rectal cancer: radiation for all?

The optimal oncologic management for patients with T3N0 rectal cancer is currently controversial. Patients with pathologic T3N0 disease may have an "intermediate" risk of disease recurrence, suggesting that perhaps trimodality therapy may not be indicated for all patients. Adverse prognostic features, including a greater depth of perirectal fat invasion, poor tumor differentiation, the presence of lymphovascular invasion, abnormally elevated pretreatment carcinoembryonic antigen levels (>5 ng/mL), circumferential margin involvement, and a low-lying position may identify T3N0 patients at high risk for local recurrence who may benefit from the addition of radiation therapy. However, recent randomized data suggest an improvement in local control and disease-free survival with preoperative radiation therapy compared with selective postoperative radiation therapy in all patient subgroups, arguing in favor of routine preoperative therapy. Additionally, rates of clinical understaging may exceed 20%, representing the percentage of patients who would require the delivery of postoperative radiotherapy with its associated sequelae. Future prospective randomized studies of T3N0 patients with upfront stratification by known prognostic factors and studies evaluating the molecular profile of rectal cancers hold the promise of better classifying patients at high risk of local and systemic recurrence, and thus, in need of adjuvant radiation and chemotherapy.     

5‐HT3 antiemetic therapy for patients with breast cancer

Antiemetic treatment should be considered for breast cancer patients receiving moderately emetogenic chemotherapy. Although the extent of chemotherapyinduced emesis is largely dependent on the emetogenic potential of the specific agents employed, patient characteristics such as age and sex also contribute. Recent clinical studies show that treatment with the currently available 5HT₃ antagonists effectively reduces the incidence of chemotherapyinduced nausea and vomiting and improves quality of life in a substantial number of these patients.A Medline search from 1994 through February 1998 identified clinical trials that included previously untreated breast cancer patients using antiemetic therapy such as granisetron, ondansetron, dolasetron, and metoclopramide.The studies reviewed here indicate that the antiemetic efficacy of 5HT₃ antagonists is equivalent in previously untreated patients receiving moderately emetogenic chemotherapy for breast cancer, depending on the doses and schedules utilized. In particular, two comparative studies of granisetron and ondansetron with specific data for breast cancer patients showed that both agents eliminate nausea in approximately 50%, and vomiting in 60–70% of these patients, with the higher values observed when steroids were added to the 5HT₃ receptor antagonist regimen.Although the chemotherapy regimens employed for breast cancer are considered only moderately emetogenic, these regimens account for 60–90% of patients experiencing nausea and vomiting. The most recent clinical studies demonstrate that 5HT₃ antagonists can significantly reduce the incidence of nausea in breast cancer patients receiving moderately emetogenic chemotherapy and should be employed in this setting.     

Are class II phosphoinositide 3-kinases potential targets for anticancer therapies?

Of the three classes of true phosphoinositide (PI) 3-kinases, the class II subdivision, which consists of three isoforms, PI3K-C2alpha, PI3K-C2beta and PI3K-C2gamma, is the least well understood. There are a number of reasons for this. This class of PI 3-kinase was identified exclusively by PCR and homology cloning approaches and not on the basis of cellular function. Like class I PI 3-kinases, class II PI 3-kinases are activated by diverse receptor types. To complicate the elucidation of class II PI 3-kinase function further, their in vitro substrate specificity is intermediate between the receptor activated class I PI 3-kinases and the housekeeping class III PI 3-kinase. The class II PI 3-kinases are inhibited by the two commonly used PI 3-kinase family selective inhibitors, wortmannin and LY294002, and there are no widely available, specific inhibitors for the individual classes or isoforms. Here the current state of understanding of class II PI 3-kinase function is reviewed, followed by an appraisal as to whether there is enough evidence to suggest that pharmaceutical companies, who are currently targeting the class I PI 3-kinases in an attempt to generate anticancer agents, should also consider targeting the class II PI 3-kinases.     

Can Glypican3 be Diagnostic for Early Hepatocellular Carcinoma among Egyptian Patients?

Background: Because of the high prevalence of hepatocellular carcinoma (HCC) in Egypt, new markerswith better diagnostic performance than alpha-feto protein (AFP) are needed to help in early diagnosis. Theaim of this work was to compare the clinical utility of both serum and mRNA glypican3 (GPC3) as probablediagnostic markers for HCC among Egyptian patients. Materials and Methods: A total of 60 subjects, including40 with HCC, 10 with cirrhosis and 10 normal controls were analyzed for serum GPC3 (sGPC3) by ELISA.GPC-3 mRNA from circulating peripheral blood mononuclear cells was amplified by RT-PCR. Both markerswere compared to some prognostic factors of HCC, and sensitivity of both techniques was compared. Results:Serum glypican-3 and AFP were significantly higher in the HCC group compared to cirrhotic and normal controls(p<0.001). Sensitivity and specificity were (95% each) for sGlypican-3, (82.5% and 85%) for AFP, and (100% and90%) for Glypican3 mRNA , and (80% and 95%) for double combination between sGPC3 and AFP respectively.Conclusion: Both serum GPC-3 and GPC-3mRNA are promising diagnostic markers for early detection of HCCin Egyptian patients. RT- PCR proved to be more sensitive (100%) than ELISA (95%) in detecting glypican3.     

COP9 signalosome subunit 6 stabilizes COP1, which functions as an E3 ubiquitin ligase for 14-3-3σ

14-3-3σ, a gene upregulated by p53 in response to DNA damage, exists as part of a positive-feedback loop, which activates p53 and is a human cancer epithelial marker downregulated in various cancer types. 14-3-3σ levels are critical for maintaining p53 activity in response to DNA damage and regulating signal mediators such as Akt. In this study, we identify mammalian constitutive photomorphogenic 1 (COP1) as a novel E3 ubiquitin ligase for targeting 14-3-3σ through proteasomal degradation. We show for the first time that COP9 signalosome subunit 6 (CSN6) associates with COP1 and is involved in 14-3-3σ ubiquitin-mediated degradation. Mechanistic studies show that CSN6 expression leads to stabilization of COP1 through reducing COP1 self-ubiquitination and decelerating COP1's turnover rate. We also show that CSN6-mediated 14-3-3σ ubiquitination is compromised when COP1 is knocked down. Thus, CSN6 mediates 14-3-3σ ubiquitination through enhancing COP1 stability. Subsequently, we show that CSN6 causes 14-3-3σ downregulation, thereby activating Akt and promoting cell survival. Also, CSN6 overexpression leads to increased cell growth, transformation and promotes tumorigenicity. Significantly, 14-3-3σ expression can correct the abnormalities mediated by CSN6 expression. These data suggest that the CSN6-COP1 axis is involved in 14-3-3σ degradation, and that deregulation of this axis will promote cell growth and tumorigenicity.     

CARMA3 is crucial for EGFR-Induced activation of NF-κB and tumor progression

EGF activates NF-κB, and constitutively activated NF-κB contributes to EGFR mutation-associated tumorigenesis, but it remains unclear precisely how EGFR signaling leads to NF-κB activation. Here we report that CARMA3, a caspase recruitment domain (CARD)-containing scaffold molecule, is required for EGF-induced NF-κB activation. CARMA3 deficiency impaired the activation of the IKK complex following EGF stimulation, resulting in a defect of EGF-induced IκBα phosphorylation and NF-κB activation. We found that CARMA3 and Bcl10 contributed to several characteristics of EGFR-associated malignancy, including proliferation, survival, migration, and invasion. Most importantly, CARMA3 contributed to tumor growth in vivo. Our findings elucidate a crucial link between EGFR-proximal signaling components and the downstream IKK complex, and they suggest a new therapeutic target for treatment of EGFR-driven cancers.     

Is the renal dosimetry for [90Y-DOTA0,Tyr3]octreotide accurate enough to predict thresholds for individual patients?

The accuracy in the dosimetry for radionuclide therapy shows a great contrast to that obtained in external beam radiotherapy. The dosimetry for [(90)Y-DOTA(0), Tyr(3)] octreotide is evaluated in patients to see whether the accuracy of the dosimetry is high enough to distinguish the probability for radiation nephropathy. The 5% threshold for late end-point nephropathy at 23 Gy with external beam radiotherapy becomes with (90)Y therapy at least 30-35 Gy, when it is given in three or more fractions. More accurate linear-quadratic (LQ) model parameters are, however, needed to predict a more precise threshold for renal damage in this dose rate region. The average MIRD-based dose to the kidneys was 27 +/- 4 Gy (N = 52) with no evidence for renal damage. The variance in the dose is only caused by the high variability in renal uptake kinetics of the compound. Using the actual kidney volumes instead of the phantom values lowered the kidney dose considerably, but the variance in the dose greatly increased. As the peptide specifically localizes in the kidney cortex, the dose to the cortex increased up to a factor 1.5 compared to the MIRD whole kidney dose. Both the sum of uncertainties of ? 40% in the actual dose to the kidneys and the unknown maximum tolerable kidney dose for internal therapy make that a fixed injected activity of 13.32 GBq together with a patient-averaged dosimetry is as good as patient-kinetics specific dosimetry using the MIRD method.     

ERBB3 is required for tumor promotion in a mouse model of?skin carcinogenesis

The epidermal growth factor receptor (EGFR) plays a key role in skin inflammation, wound healing, and carcinogenesis. Less is known about the functions of the structurally related receptor ERBB3 (HER3) in the skin. We assessed the requirement of ERBB3 for skin homeostasis, wound healing, and tumorigenesis by crossing mice carrying a conditional Erbb3 allele with animals expressing cre under the control of the keratin 5 promoter. Erbb3del mice, lacking ERBB3 specifically in keratinocytes, showed no obvious abnormalities. The EGFR was upregulated in Erbb3del skin, possibly compensating the loss of ERBB3. Nonetheless, healing of full‐thickness excisional wounds was negatively affected by ERBB3 deficiency. To analyze the function of ERBB3 during tumorigenesis, we employed the established DMBA/TPA multi‐stage chemical carcinogenesis protocol. Erbb3del mice remained free of papillomas for a longer time and had significantly reduced tumor burden compared to control littermates. Tumor cell proliferation was considerably reduced in Erbb3del mice, and loss of ERBB3 also impaired keratinocyte proliferation after a single application of TPA. In human skin tumor samples, upregulated ERBB3 expression was observed in squamous cell carcinoma, condyloma, and malignant melanoma. Thus, we conclude that ERBB3, while dispensable for the development and the homeostasis of the epidermis and its appendages, is required for proper wound healing and for the progression of skin tumors during multi‐stage chemical carcinogenesis in mice. ERBB3 may also be important for human skin cancer progression. The latter effects most probably reflect a key role for ERBB3 in increasing cell proliferation after stimuli as wounding or carcinogenesis.     

Preclinical Rationale for PI3K/Akt/mTOR Pathway Inhibitors as Therapy for Epidermal Growth Factor Receptor Inhibitor-Resistant Non–Small-Cell Lung Cancer

Mutations in the epidermal growth factor receptor gene (EGFR) are frequently observed in non–small-cell lung cancer (NSCLC), occurring in about 40% to 60% of never-smokers and in about 17% of patients with adenocarcinomas. EGFR tyrosine kinase inhibitors (TKIs), such as gefitinib and erlotinib, have transformed therapy for patients with EGFR-mutant NSCLC and have proved superior to chemotherapy as first-line treatment for this patient group. Despite these benefits, there are currently 2 key challenges associated with EGFR inhibitor therapy for patients with NSCLC. First, only 85% to 90% of patients with the EGFR mutation derive clinical benefit from EGFR TKIs, with the remainder demonstrating innate resistance to therapy. Second, acquired resistance to EGFR TKIs inevitably occurs in patients who initially respond to therapy, with a median duration of response of about 10 months.Mutant EGFR activates various subcellular signaling cascades, including the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) pathway, which demonstrates maintained activity in a variety of TKI-resistant cancers. Given the fundamental role of the PI3K/Akt/mTOR pathway in tumor oncogenesis, proliferation, and survival, PI3K pathway inhibitors have emerged as a possible solution to the problem of EGFR TKI resistance. However resistance to EGFR TKIs is associated with considerable heterogeneity and complexity. Preclinical experiments investigating these phenomena suggest that in some patients, PI3K inhibitors will have to be paired with other targeted agents if they are to be effective. This review discusses the preclinical data supporting PI3K/Akt/mTOR pathway inhibitor combinations in EGFR TKI-resistant NSCLC from the perspective of the various agents currently being investigated in clinical trials.     

Quit Smoking for Life—Social Marketing Strategy for Youth: A Case for Pakistan

Smoking is the single most avoidable risk factor for cancers. Majority of smokers know about this fact but it is difficult for them to give it up mainly in the face of widespread smoking advertisements by the tobacco industries. To reduce the prevalence of smoking and its associated cancers, immediate actions are required by public health authorities. Social marketing is an effective strategy to promote healthy attitudes and influence people to make real, sustained health behavior change by transiting through different stages which include precontemplation, contemplation, preparation, action, and maintenance. Social marketing can influence smokers to voluntarily accept, reject, modify, or abandon their smoking behavior. In Pakistan, the smoking prevalence has been increasing, necessitating effective measures. The trend of its usage has been going upwards and, according to the World Health Organization, in Pakistan, the usage of cigarette smoking is increased by 30% compared to 1998 figures. The Pakistan Pediatrics Association has estimated 1,000 to 1,200 school-going children between the ages of 6 and 16 years take up smoking every day. In Pakistan, ex-smokers in the low socioeconomic group reported spending 25% of the total household income on this habit. This paper focuses on the antismoking social marketing strategy in Pakistan with an aim to reduce smoking prevalence, especially among the youth.     

Synchronization of cells in the S phase of the cell cycle by 3′-azido-3′-deoxythymidine: implications for cell cytotoxicity

The mechanism of synergy between 3-azido-3-deoxythymidine (AZT) and anticancer agents was inverstigated with emphasis on cell-cycle events. Exposure of exponentially growing WiDr human colon carcinoma cells to AZT resulted in synchronization of cells in the S phase of the cell cycle. Forllowing treatment with AZT at 50 or 200 M, 62%±3% or 82%±4% of the cells were in the S phase as compared with 36%±2% in the control. Bromodeoxyuridine uptake studies revealed that the synchronized cells actively synthesized DNA. At concentrations of up to 200 M, AZT produced a cytostatic rather than cytotoxic effect as indicated by viability and cell growth measurements. at 200 M, AZT-induced synchronization was significant (P=<0.001) after 12 h of drug exposure, reached a maximum at 24 h, and reversed to baseline levels by 72 h even in the continued presence of the drug. This indicates that AZT-induced cytostasis is a transient and reversible effect. The cell-cycle events seen with AZT in WiDr cells were also observed in eight of nine human tumor cell lines tested. Isobologram analysis of WiDr cells preexposed to AZT for 24 h and then exposed to either AZT-5-fluorouracil or AZT-methotrexate for a further 72 h revealed synergy between AZT and the anticancer agents, indicating that AZT-induced synchronization may have therapeutic benefits.Abbreviations AZT 3-Azido-3-deoxythymidine - 5-FU 5-fluorouracil - MTX methotrexate - BrdUrd bromodeoxyuridine - MTT 3-(4-5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide