Human papillomavirus type 16 E7 up-regulates AKT activity through the retinoblastoma protein

Human papillomaviruses (HPV) are small DNA tumor viruses causally associated with cervical cancer. The early gene product E7 from high-risk HPV is considered the major transforming protein expressed by the virus. Although many functions have been described for E7 in disrupting normal cellular processes, we describe in this study a new cellular target in primary human foreskin keratinocytes (HFK), the serine/threonine kinase AKT. Expression of HPV type 16 E7 in HFK caused inhibition of differentiation, hyperproliferation, and up-regulation of AKT activity in organotypic raft cultures. The ability of E7 to up-regulate AKT activity is dependent on its ability to bind to and inactivate the retinoblastoma (Rb) gene product family of proteins. Furthermore, we show that knocking down Rb alone, with short hairpin RNAs, was sufficient to up-regulate AKT activity in differentiated keratinocytes. Up-regulation of AKT activity and loss of Rb was also observed in HPV-positive cervical high-grade squamous intraepithelial lesions when compared with normal cervical tissue. Together, these data provide evidence linking inactivation of Rb by E7 in the up-regulation of AKT activity during cervical cancer progression.     

Alcohol Intake and Risk of Breast Cancer by Histologic Subtype and Estrogen Receptor Status Among Women Aged 55 to 74 Years

Previous studies suggest that alcohol consumption and risk of breast cancer may differ by histologic subtype and hormone receptor status, though results are not entirely consistent. In this population-based case-control study, we evaluated the association between alcohol consumption and risk of invasive ductal carcinoma (IDC), invasive lobular carcinoma (ILC), and invasive ductal-lobular carcinoma (IDLC) overall and by estrogen receptor (ER) status, among women aged 55–74 years of age. Using polytomous regression, associations between current alcohol consumption, overall and by type of alcohol, and breast cancer risk were evaluated in 891 controls and 905 IDC, 567 ILC, and 489 IDLC cases. Current alcohol use was moderately associated with risk of ILC (odds ratio = 1.25, 95% confidence interval 0.99, 1.58) with a positive dose-response relationship based on average number of drinks per week consumed (P _trend = 0.0005). When further stratified by ER status, alcohol use was positively associated with risk of ER+ ILC (P _trend = 0.002) and ER+ IDC (P _trend = 0.02), but inversely associated with risk of ER?IDC (P _trend = 0.01). No association between alcohol and risk of IDLC tumors was observed. While the link between alcohol consumption and breast cancer risk is well established, our results suggest that the increased risk associated with alcohol is largely limited to ER+ ILC and ER+ IDC. Thus, avoiding or moderating alcohol consumption may be one way that women can lower their risks of these forms of breast cancer.     

Nuclear ribonucleoprotein release and nucleoside triphosphatase activity are inhibited by antibodies directed against one nuclear matrix glycoprotein.

Circumstantial evidence suggests that nucleocytoplasmic exchange or transport is an active process involving the nuclear pore complex of the nuclear envelope. To test this hypothesis, antibodies were generated against nuclear envelope components from a highly enriched pore complex fraction from Spisula solidissima oocytes. Some of these antibodies inhibited ATP-dependent ribonucleoprotein release from prelabeled, isolated rat nuclei and inhibited nucleoside triphosphatase activity essential in nucleocytoplasmic transport. Inhibition of both functions by lectins indicated that the antigen was a glycoprotein. It was identified as lamin B, a major component of the nuclear envelope and nuclear matrix. This glycoprotein may not only be a structural nuclear protein but also may have nucleoside triphosphatase activity. We speculate that lamin B represents the solid support for ribonucleoprotein transport. This protein is expected to be highly conserved if active transport in and out of the nucleus is essential in the eukaryotic system.     

An Epstein-Barr virus-negative Burkitt lymphoma cell line (sfRamos) secretes a prolactin-like protein during continuous growth in serum-free medium.

Pituitary human PRL (hPRL) antiserum inhibits growth of B-lymphoblastoid cells in vitro, but the mechanism of inhibition is unclear. In this study the mechanism of inhibition of human B-cell growth by anti-hPRL was explored with an Epstein-Barr virus nuclear antigen (EBNA)-negative Burkitt lymphoma cell line (sfRamos) that proliferates continuously in serum-free medium with human transferrin as the only protein supplement. The data show that antiserum immunoglobulin fraction G (IgG) to pituitary hPRL, but not nonimmune serum IgG, completely inhibited the growth of sfRamos cells. In addition, anti-hPRL IgG identified a single band (29 kDa) in sfRamos spent medium, but not in fresh serum-free medium or in human transferrin, as demonstrated by sodium dodecyl sulfate-reducing polyacrylamide gel electrophoresis and Western immunoblot analysis. Polyacrylamide gel electrophoresis and Western analysis of a mixture containing sfRamos spent medium and excess pituitary hPRL established that the sfRamos 29-kDa PRL-like protein (PLP29) and pituitary hPRL (23 kDa) were electrophoretically distinct. Finally, sfRamos spent medium, but not fresh serum-free medium, was mitogenic for sfRamos and Nb2, a PRL-sensitive node rat lymphoma cell line. These findings demonstrate that PLP29 is biologically and immunologically like pituitary hPRL, but is electrophoretically different from this hormone. We suggest that PLP29 is secreted as an autocrine growth factor by sfRamos Burkitt lymphoma cells during continuous serum-free growth.     

The association of soy food consumption with the risk of subtype of breast cancers defined by hormone receptor and HER2 status

Soy food intake has previously been associated with reduced breast cancer risk. Epidemiological evidence for subgroups of breast cancer, particularly by menopausal and hormone receptor status, is less consistent. To evaluate the role of hormone receptor and menopausal status on the association between soy food intake and breast cancer risk, we measured usual soy food intake in adolescence and adulthood via food frequency questionnaire in 70,578 Chinese women, aged 40–70 years, recruited to the Shanghai Women's Health Study (1996–2000). After a median follow‐up of 13.2 years (range: 0.01–15.0), 1,034 incident breast cancer cases were identified. Using Cox models, we found that adult soy intake was inversely associated with breast cancer risk [hazard ratio (HR) for fifth versus first quintile soy protein intake = 0.78; 95% confidence interval (CI):0.63–0.97]. The association was predominantly seen in premenopausal women (HR = 0.46; 95% CI:0.29‐0.74). Analyses further stratified by hormone receptor status showed that adult soy intake was associated with significantly decreased risk of estrogen receptor (ER)+/progesterone receptor (PR)+ breast cancer in postmenopausal women (HR = 0.72; 95% CI:0.53–0.96) and decreased risk of ER?/PR? breast cancer in premenopausal women (HR = 0.46; 95% CI:0.22–0.97). The soy association did not vary by human epidermal growth factor‐2 (HER2) status. Furthermore, we found that high soy intake during adulthood and adolescence was associated with reduced premenopausal breast cancer risk (HR = 0.53; 95% CI: 0.32–0.88; comparing third vs. first tertile) while high adulthood soy intake was associated with postmenopausal breast cancer only when adolescent intake was low (HR = 0.63; 95% CI: 0.43–0.91). Our study suggests that hormonal status, menopausal status and time window of exposure are important factors influencing the soy‐breast cancer association.     

Alcohol,smoking, and risk of Her2‐overexpressing and triple‐negative breast cancer relative to estrogen receptor‐positive breast cancer

Epidemiological evidence is limited on how alcohol consumption and smoking are associated with risk of different subtypes of breast cancer, such as triple‐negative (TN) and human epidermal growth factor receptor 2‐overexpressing (H2E) breast cancers, which may have different etiologies from more common luminal (estrogen receptor [ER+]) breast cancers. In this population‐based case‐case study, we evaluated the association between alcohol, smoking, and risk of H2E and TN breast cancer, compared with ER+ breast cancers, among women aged 20–69 years. Using polytomous regression, associations between alcohol consumption, smoking, and breast cancer risk were evaluated in 909 ER+, 1,290 TN, and 489 H2E breast cancer patients, with ER+ breast cancer patients as the reference group. Current alcohol consumption at diagnosis was associated with a lower risk of H2E breast cancer (odds ratio = 0.74, 95% confidence interval: 0.58–0.92) relative to ER+ cancers. No difference in association was observed by menopausal status. No association between alcohol consumption and TN breast cancer relative to ER+ breast cancer was observed. Women who smoked did not have an altered risk of TN or H2E breast cancer, relative to ER+ cancer. Our results suggest that alcohol is associated with lower risk of H2E breast cancer relative to ER+ breast cancer. This study adds to the body of epidemiologic evidence that breast cancer etiology differs by breast cancer subtype.     

Defective binding of factor XI-N248 to activated human platelets.

Variants of factor XI containing Gln226 to Arg (Q226 to R) and Ser248 to Asn (S248 to N) substitutions were first identified in an African American family with a history of excessive bleeding. The substitutions have recently been identified in unrelated individuals, suggesting they are relatively common. Both amino acids are located in the third apple domain of factor XI, an area implicated in binding interactions with factor IX and activated platelets. Recombinant factor XI-R226 and factor XI-N248 were compared with wild-type factor XI in assays for factor IX activation or platelet binding. Factor XI-R226 activates factor IX with a Michaelis-Menten constant (K(m)) about 5-fold greater than wild-type protein. The catalytic efficiency of factor IX activation is similar to wild-type protein, however, due to an increase in the turnover number (k(cat)) for the reaction. Iodinated factor XI-N248 binds to activated platelets with a dissociation constant (K(d)) more than 5-fold higher than wild-type protein (55 nM and 10 nM, respectively). Activation of factor XI-N248 by thrombin in the presence of activated platelets is slower and does not progress to the same extent as activation of the wild-type protein under similar conditions. Factor XI-N248 activates factor IX normally in a purified protein system and has relatively normal activity in activated partial thromboplastin time (aPTT) assays. Factor XI-N248 is the first factor XI variant described with a clear functional difference compared with wild-type protein. Importantly, the defect in platelet binding would not be detected by routine clinical evaluation with an aPTT assay.