Abstract
The fate of stars in the zero-age main-sequence (ZAMS) range ≈8–12
M
⊙
is unclear. They could evolve to form white dwarfs or explode as electron-capture supernovae (SNe) or iron ...core-collapse SNe (CCSNe). Even though the initial mass function indicates that this mass range should account for over 40% of all CCSN progenitors, few have been observationally confirmed, likely due to the faintness and rapid evolution of some of these transients. In this paper, we present a sample of nine Ca-rich/O-poor Type IIb SNe detected by the Zwicky Transient Facility with progenitors likely in this mass range. These sources have a Ca
ii
λ
λ
7291, 7324/O
i
λ
λ
6300, 6364 flux ratio of ≳2 in their nebular spectra. Comparing the measured O
i
luminosity (≲10
39
erg s
−1
) and derived oxygen mass (≈0.01
M
⊙
) with theoretical models, we infer that the progenitor ZAMS mass for these explosions is less than 12
M
⊙
. The ejecta properties (
M
ej
≲ 1
M
⊙
and
E
kin
∼ 10
50
erg) are also consistent. The low ejecta mass of these sources indicates a class of strongly-stripped SNe that is a transition between the regular stripped-envelope SNe and ultra-stripped SNe. The progenitor could be stripped by a main-sequence companion and result in the formation of a neutron star−main sequence binary. Such binaries have been suggested to be progenitors of neutron star−white dwarf systems that could merge within a Hubble time and be detectable with LISA.
The fate of stars in the zero-age main-sequence (ZAMS) range \(\approx 8-12\) Msun is unclear. They could evolve to form white dwarfs or explode as electron-capture supernovae (SNe) or iron ...core-collapse SNe (CCSNe). Even though the initial mass function indicates that this mass range should account for over 40% of all CCSNe progenitors, few have been observationally confirmed, likely owing to the faintness and rapid evolution of these transients. In this paper, we present a sample of nine Ca-rich/O-poor Type IIb SNe detected by the Zwicky Transient Facility with progenitors likely in this mass range. We perform a holistic analysis of the spectroscopic and photometric properties of the sample. These sources have a flux ratio of Ca II \(\lambda \lambda\)7291, 7324 to O I \(\lambda \lambda\)6300, 6364 of \(\gtrsim\) 2 in their nebular spectra. Comparing the measured O I luminosity (\(\lesssim 10^{39} \mathrm{erg\ s^{-1}}\)) and derived oxygen mass (\(\lesssim 0.1\) Msun) with theoretical models, we infer that the progenitor ZAMS mass for these explosions is less than 12 Msun. These correspond to He-stars with core masses less than around 3 Msun. We find that the ejecta properties (Mej \(\lesssim 1\) Msun) are also consistent with those expected for such low mass He-stars. The low ejecta mass of these sources indicates a class of strongly-stripped SNe that is a transition between the regular stripped-envelope SNe and ultra-stripped SNe. The progenitor could be stripped by a main sequence companion and result in the formation of a neutron star \(-\) main sequence binary. Such binaries have been suggested to be progenitors of neutron star \(-\) white dwarf systems that could merge within a Hubble time, and be detectable with LISA.
Background
The anti‐tumor immune response plays a key role in colorectal cancer (CRC) progression and survival. The T cell‐inflamed gene expression profile (GEP) is a biomarker predicting response to ...checkpoint inhibitor immunotherapy across immunogenic cancer types, but the prognostic value in CRC is unknown. We evaluated associations with disease‐specific survival, somatic mutations, and examined its differentially expressed genes and pathways among 84 sporadic CRC patients from the Seattle Colon Cancer Family Registry.
Methods
Gene expression profiling was performed using Nanostring's nCounter PanCancer IO 360 panel. Somatic mutations were identified by a targeted DNA sequencing panel.
Results
The T cell‐inflamed GEP was positively associated with tumor mutation burden and microsatellite instability high (MSI‐H). Higher T cell‐inflamed GEP had favorable CRC‐specific survival (hazard ratio HR per standard deviation unit = 0.50, p = 0.004) regardless of hypermutation or MSI status. Analysis of recurrently mutated genes having at least 10 mutation carriers, suggested that the T cell‐inflamed GEP is positively associated with RYR1, and negatively associated with APC. However, these associations were attenuated after adjusting for hypermutation or MSI status. We also found that expression of genes RPL23, EPCAM, AREG and ITGA6, and the Wnt signaling pathway was negatively associated with the T cell‐inflamed GEP, which might indicate immune‐inhibitory mechanisms.
Conclusions
Our results show that the T cell‐inflamed GEP is a prognostic biomarker in non‐hypermutated microsatellite‐stable CRC. This also suggests that patient stratification for immunotherapy within this CRC subgroup should be explored further. Moreover, reported immune‐inhibitory gene expression signals may suggest targets for therapeutic combination with immunotherapy.
T cell‐inflamed gene expression profile score, a biomarker predicting immune checkpoint inhibitor responses, is related to colorectal cancer (CRC)‐specific survival among non‐hypermutated and microsatellite stable patients, a group refractory to immunotherapy. Our finding suggests that patient stratification for immunotherapy within this CRC subgroup should be explored further.
