The mechanisms by which neural stem cells give rise to neurons, astrocytes, or oligodendrocytes are beginning to be elucidated. However, it is not known how the specification of one cell lineage results in the suppression of alternative fates. We find that in addition to inducing neurogenesis, the bHLH transcription factor neurogenin (Ngn1) inhibits the differentiation of neural stem cells into astrocytes. While Ngn1 promotes neurogenesis by functioning as a transcriptional activator, Ngn1 inhibits astrocyte differentiation by sequestering the CBP-Smad1 transcription complex away from astrocyte differentiation genes, and by inhibiting the activation of STAT transcription factors that are necessary for gliogenesis. Thus, two distinct mechanisms are involved in the activation and suppression of gene expression during cell-fate specification by neurogenin.

A B S T R A C T PurposeThe purpose of this study was to characterize suicide rates among patients with cancer in the United States and identify patient and disease characteristics associated with higher suicide rates. Prior studies, mostly in Europe, have suggested that patients with cancer may be at increased risk for suicide, but large cohort studies comparing patients with cancer with the general population have not been performed in the United States. MethodsPatients in the study were residents of geographic areas served by the Surveillance, Epidemiology, and End Results (SEER) program who were diagnosed with cancer from 1973 to 2002. Comparisons with the general US population were based on mortality data collected by the National Center for Health Statistics. This was a retrospective cohort study of suicide in persons with cancer. ResultsAmong 3,594,750 SEER registry patients observed for 18,604,308 person-years, 5,838 suicides were identified, for an age-, sex-, and race-adjusted rate of 31.4/100,000 person-years. In contrast, the suicide rate in the general US population was 16.7/100,000 person-years. Higher suicide rates were associated with male sex, white race, and older age at diagnosis. The highest suicide risks were observed in patients with cancers of the lung and bronchus (standardized mortality ratio [SMR] ϭ 5.74; 95% CI, 5.30 to 6.22), stomach (SMR ϭ 4.68; 95% CI, 3.81 to 5.70), oral cavity and pharynx (SMR ϭ 3.66; 95% CI, 3.16 to 4.22), and larynx (SMR ϭ 2.83; 95% CI, 2.31 to 3.44). SMRs were highest in the first 5 years after diagnosis with cancer. ConclusionPatients with cancer in the United States have nearly twice the incidence of suicide of the general population, and suicide rates vary among patients with cancers of different anatomic sites. Further examination of the psychological experience of patients with cancer, particularly that of patients with certain types of cancer, is warranted.