Intercellular signaling through the cell-surface receptor Notch plays important roles in a variety of developmental processes as well as in pathogenesis of some human cancers and genetic disorders. However, the mechanisms by which Notch signals are transduced into cells still remain elusive. Here we investigated the signaling mechanisms for Notch in the cell fate control of neural progenitor cells. We show that Deltex-1 (DTX1), a mammalian homolog of Drosophila Deltex, mediates a Notch signal to block differentiation of neural progenitor cells. We found that a significant fraction of DTX1 proteins were localized in the nucleus and physically interacted with the transcriptional coactivator p300. Through its binding to p300, DTX1 inhibited transcriptional activation by the neural-specific helix-loop-helixtype transcription factor MASH1, and this mechanism is likely responsible for the differentiation inhibition of neural progenitor cells. Our results further suggest that DTX1 regulates transcription independently of the previously characterized Notch signaling pathway involving RBP-J and HES1/HES5. Thus, DTX1 serves as an important signaling component downstream of Notch that regulates transcription in the nucleus.

Fluorogenic probes in the near-infrared (NIR) region have the potential to provide stimuli-dependent information in living organisms. Here, we describe a new class of fluorogenic probes based on the heptamethine cyanine scaffold, the most broadly used NIR chromophore. These compounds result from modification of heptamethine norcyanines with stimuli-responsive carbamate linkers. The resulting cyanine carbamates (CyBams) exhibit exceptional turn-ON ratios (∼170×) due to dual requirements for NIR emission: carbamate cleavage through 1,6-elimination and chromophore protonation. Illustrating their utility in complex in vivo settings, a γ-glutamate substituted CyBam was applied to imaging γ-glutamyl transpeptidase (GGT) activity in a metastatic model of ovarian cancer. Overall, CyBams have significant potential to extend the reach of fluorogenic strategies to intact tissue and live animal imaging applications.

Near-infrared photoimmunotherapy (NIR-PIT) is a newly developed and selective cancer treatment that induces necrotic and immunogenic cell death and utilizes a mAb conjugated to a photo-absorber dye, IR700DX, activated by NIR light. Although CD44 is a surface cancer marker associated with drug resistance, anti-CD44-IR700 NIR-PIT results in inhibited cell growth and prolonged survival in multiple tumor types. Meanwhile, CD25targeted NIR-PIT has been reported to achieve selective and local depletion of FOXP3 þ CD25 þ CD4 þ regulatory T cells (Treg), which are primary immunosuppressive cells in the tumor microenvironment (TME), resulting in activation of local antitumor immunity. Combined NIR-PIT with CD44-and CD25-targeted agents has the potential to directly eliminate tumor cells and also amplify the immune response by removingTregs from the TME. We investigated the difference in therapeutic effects of CD44-targeted NIR-PIT alone, CD25-targeted NIR-PIT alone, and the combination of CD44-and CD25-targeted NIR-PIT in several syngeneic tumor models, including MC38-luc, LL/2, and MOC1. The combined NIR-PIT showed significant tumor growth inhibition and prolonged survival compared with CD44-targeted NIR-PIT alone in all tumor models and showed prolonged survival compared with CD25-targeted NIR-PIT alone in MC38-luc and LL/2 tumors. Combined CD44-and CD25-targeted NIR-PIT also resulted in some complete remissions. Therefore, combined NIR-PIT simultaneously targeting cancer antigens and immunosuppressive cells in the TME may be more effective than either type of NIR-PIT alone and may have potential to induce prolonged immune responses in treated tumors.