Premenopausal plasma 25-hydroxyvitamin D,mammographic density,and risk of breast cancer

Breast Cancer Research and Treatment - Epidemiologic evidence for an association between plasma 25-hydroxyvitamin D [25(OH)D] and breast cancer is inconsistent. Data are especially limited for...     

Irinotecan treatment and senescence failure promote the emergence of more transformed and invasive cells that depend on anti-apoptotic Mcl-1

Induction of senescence by chemotherapy was initially characterized as a suppressive response that prevents tumor cell proliferation. However, in response to treatment, it is not really known how cells can survive senescence and how irreversible this pathway is. In this study, we analyzed cell escape in response to irinotecan, a first line treatment used in colorectal cancer that induced senescence. We detected subpopulations of cells that adapted to chemotherapy and resumed proliferation. Survival led to the emergence of more transformed cells that induced tumor formation in mice and grew in low adhesion conditions. A significant amount of viable polyploid cells was also generated following irinotecan failure. Markers such as lgr5, CD44, CD133 and ALDH were downregulated in persistent clones, indicating that survival was not associated with an increase in cancer initiating cells. Importantly, malignant cells which resisted senescence relied on survival pathways induced by Mcl-1 signaling and to a lesser extent by Bcl-xL. Depletion of Mcl-1 increased irinotecan efficiency, induced the death of polyploid cells, prevented cell emergence and inhibited growth in low-adhesion conditions. We therefore propose that Mcl-1 targeting should be considered in the future to reduce senescence escape and to improve the treatment of irinotecan-refractory colorectal cancers.     

Disrupting LIN28 in atypical teratoid rhabdoid tumors reveals the importance of the mitogen activated protein kinase pathway as a therapeutic target

Atypical teratoid rhabdoid tumor (AT/RT) is among the most fatal of all pediatric brain tumors. Aside from loss of function mutations in the SMARCB1 (BAF47/INI1/SNF5) chromatin remodeling gene, little is known of other molecular drivers of AT/RT. LIN28A and LIN28B are stem cell factors that regulate thousands of RNAs and are expressed in aggressive cancers. We identified high-levels of LIN28A and LIN28B in AT/RT primary tumors and cell lines, with corresponding low levels of the LIN28-regulated microRNAs of the let-7 family. Knockdown of LIN28A by lentiviral shRNA in the AT/RT cell lines CHLA-06-ATRT and BT37 inhibited growth, cell proliferation and colony formation and induced apoptosis. Suppression of LIN28A in orthotopic xenograft models led to a more than doubling of median survival compared to empty vector controls (48 vs 115 days). LIN28A knockdown led to increased expression of let-7b and let-7g microRNAs and a down-regulation of KRAS mRNA. AT/RT primary tumors expressed increased mitogen activated protein (MAP) kinase pathway activity, and the MEK inhibitor selumetinib (AZD6244) decreased AT/RT growth and increased apoptosis. These data implicate LIN28/RAS/MAP kinase as key drivers of AT/RT tumorigenesis and indicate that targeting this pathway may be a therapeutic option in this aggressive pediatric malignancy.     

Determination of free testosterone fraction of human serum by gel bead dialysis

The gel bead dialysis technique is an application of the steady-state gel filtration method. Preswollen gel beads are used as microdialysers. The gel is incubated for 3.5 h at 22 degrees C with 2.5 mL of serum and 3H-testosterone. During incubation, the equilibrium between free and protein-bound fractions is reached and the concentration of testosterone in the bead dialysate is equal to the free testosterone concentration in the incubation medium surrounding the beads. After incubation, the gel is separated from the medium by using a rigid filter and the radioactivity within the gel is counted. The effect on the assay of serum dilution and incubation time were studied. Within-batch imprecision (CV) was 3% (N = 30) and between-batch imprecision computed from lyophilized quality controls run over a one year-period, was 7%, 13% and 17% for free testosterone fractions (free over total) of 0.043, 0.032 and 0.021 respectively. An excellent correlation between this technique and the equilibrium dialysis method was found (r = 0.944, N = 59). Reference intervals were determined for men, women and pregnant women; mean +/- SD were 0.0216 +/- 0.0067 (N = 20), 0.0106 +/- 0.0020 (N = 20) and 0.0077 +/- 0.0017 (N = 19) respectively. Patients suffering from polycystic ovary syndrome had significantly higher free testosterone ratio (mean of 0.0285 +/- 0.0074, N = 20) than normal females.