Predictive Signatures for Responses to Checkpoint Blockade in Small-Cell Lung Cancer in Second-Line Therapy Do Not Predict Responses in First-Line Patients.

Although immune checkpoint blockade (ICB) is currently approved for the treatment of extensive-stage small-cell lung cancer (SCLC) in combination with chemotherapy, relatively few patients have demonstrated durable clinical benefit (DCB) to these therapies. Biomarkers predicting responses are needed. Biopsies from 35 SCLC patients treated with ICB were subjected to transcriptomic analysis; gene signatures were assessed for associations with responses. Twenty-one patients were treated with ICB in the first-line setting in combination with platinum-based chemotherapy; fourteen patients were treated in the second-line setting with ICB alone. DCB after ICB in SCLC in the second-line setting (3 of 14 patients) was associated with statistically higher transcriptomic levels of genes associated with inflammation (p = 0.003), antigen presentation machinery (p = 0.03), interferon responses (p < 0.05), and increased CD8 T cells (p = 0.02). In contrast, these gene signatures were not significantly different in the first-line setting. Our data suggest that responses to ICB in SCLC in the second-line setting can be predicted by the baseline inflammatory state of the tumor; however, this strong association with inflammation was not seen in the first-line setting. We postulate that chemotherapy alters the immune milieu allowing a response to ICB. Other biomarkers will be needed to predict responses in first-line therapy patients.

The transcription factor Sp8 is required for the production of parvalbumin-expressing interneurons in the olfactory bulb.

Interneurons in the olfactory bulb (OB) represent a heterogeneous population, which are first produced at embryonic stages and persisting into adulthood. Using the BrdU birthdating method combined with immunostaining for several different neuronal markers, we provide the integrated temporal patterns of distinct mouse OB interneuron production from embryonic day 14 to postnatal day 365. We show that although the majority of OB interneuron subtypes continue to be generated throughout life, most subtypes show a similar "bell-like" temporal production pattern with a peak around birth. Tyrosine hydroxylase and calretinin-expressing interneurons are produced at a relatively low rate in the adult OB, while parvalbumin-expressing (PV+) interneuron production is confined to later embryonic and early postnatal stages. We also show that Dlx5/6-expressing progenitors contribute to PV+ interneurons in the OB. Interestingly, all PV+ interneurons in the external plexiform layer (EPL) express the transcription factor Sp8. Genetic ablation of Sp8 by cre/loxP-based recombination severely reduces the number of PV+ interneurons in the EPL of the OB. Our results suggest that Sp8 is required for the normal production of PV+ interneurons in the EPL of the OB. These data expand our understanding of the temporal and molecular regulation of OB interneuron neurogenesis.

Emx1-expressing neural stem cells in the subventricular zone give rise to new interneurons in the ischemic injured striatum.

Neural stem cells from different regions within the subventricular zone (SVZ) are able to produce several different subtypes of interneurons in the olfactory bulb throughout life. Previous studies have shown that ischemic stroke induces the production of new neurons in the damaged striatum from the SVZ. However, the origins and genetic profiles of these newborn neurons remain largely unknown as SVZ neural stem cells are heterogeneous. In the present study, using a mouse model of perinatal hypoxic-ischemic (H/I) brain injury combined with BrdU labeling methods, we found that, as in rat brains, virtually all newborn neuroblasts that migrate from the SVZ into the ischemic injured striatum exclusively express the transcription factor Sp8. Furthermore, although newborn neuroblasts are plentiful in the damaged striatum, only a few can differentiate into calretinin-expressing (CR+) interneurons that continuously express Sp8. Genetic fate mapping reveals that newly born CR+ interneurons are generated from Emx1-expressing neural stem cells in the dorsal-lateral SVZ. These results suggest that the fate of the Emx1-expressing lineage in the ischemic damaged striatum is restricted. However, when Sp8 was conditionally inactivated in the Emx1-lineage cells, Pax6 was ectopically expressed by a subpopulation of Emx1-derived CR+ cells in the normal and damaged striatum. Interestingly, these cells possessed large cell bodies and long processes. This work identifies the origin of the newly born CR+ interneurons in the damaged striatum after ischemic brain injury.

Sustained increase in adult neurogenesis in the rat hippocampal dentate gyrus after transient brain ischemia.

It is known that the number of newly generated neurons is increased in the young and adult rodent subventricular zone (SVZ) and dentate gyrus (DG) after transient brain ischemia. However, it remains unclear whether increase in neurogenesis in the adult DG induced by ischemic stroke is transient or sustained. We here reported that from 2 weeks to 6 months after transient middle cerebral artery occlusion (MCAO), there were more doublecortin positive (DCX+) cells in the ipsilateral compared to the sham-control and contralateral DG of the adult rat. After the S-phase marker 5-bromo-2'-deoxyuridine (BrdU) was injected 2 days after MCAO to label newly generated cells, a large number of BrdU-labeled neuroblasts differentiated into mature granular neurons. These BrdU-labeled neurons survived for at least 6 months. When BrdU was injected 6 weeks after injury, there were still more newly generated neuroblasts differentiated into mature neurons in the ipsilateral DG. Altogether, our data indicate that transient brain ischemia initiates a prolonged increase in neurogenesis and promotes the normal development of the newly generated neurons in the adult DG.