Lung squamous cell carcinoma (LSCC) is a deadly disease for which only a subset of patients responds to immune checkpoint blockade (ICB) therapy. Therefore, preclinical mouse models that recapitulate ...the complex genetic profile found in patients are urgently needed.
We used CRISPR genome editing to delete multiple tumor suppressors in lung organoids derived from Cre-dependent SOX2 knock-in mice. We investigated both the therapeutic efficacy and immunologic effects accompanying combination PD-1 blockade and WEE1 inhibition in both mouse models and LSCC patient-derived cell lines.
We show that multiplex gene editing of mouse lung organoids using the CRISPR-Cas9 system allows for efficient and rapid means to generate LSCCs that closely mimic the human disease at the genomic and phenotypic level. Using this genetically defined mouse model and three-dimensional tumoroid culture system, we show that WEE1 inhibition induces DNA damage that primes the endogenous type I IFN and antigen presentation system in primary LSCC tumor cells. These events promote cytotoxic T-cell-mediated clearance of tumor cells and reduce the accumulation of tumor-infiltrating neutrophils. Beneficial immunologic features of WEE1 inhibition are further enhanced by the addition of anti-PD-1 therapy.
We developed a mouse model system to investigate a novel combinatory approach that illuminates a clinical path hypothesis for combining ICB with DNA damage-inducing therapies in the treatment of LSCC.
The mammalian target of rapamycin (mTOR) complex 1 (mTORC1) is a nutrient-sensitive protein kinase that is aberrantly activated in many human cancers. Whether dysregulation of mTORC1 signaling in ...normal tissues increases the risk for cancer, however, is unknown. We focused on hepatocellular carcinoma, which has been linked to environmental factors that affect mTORC1 activity, including diet. Ablation of the gene encoding TSC1 (tuberous sclerosis complex 1), which as part of the TSC1-TSC2 complex is an upstream inhibitor of mTORC1, results in constitutively increased mTORC1 signaling, an effect on this pathway similar to that of obesity. We found that mice with liver-specific knockout of Tsc1 developed sporadic hepatocellular carcinoma with heterogeneous histological and biochemical features. The spontaneous development of hepatocellular carcinoma in this mouse model was preceded by a series of pathological changes that accompany the primary etiologies of this cancer in humans, including liver damage, inflammation, necrosis, and regeneration. Chronic mTORC1 signaling led to unresolved endoplasmic reticulum stress and defects in autophagy, factors that contributed to hepatocyte damage and hepatocellular carcinoma development. Therefore, we conclude that increased activation of mTORC1 can promote carcinogenesis and may thus represent a key molecular link between cancer risk and environmental factors, such as diet.
Patients with lung cancer often present with metastatic disease and therefore have a very poor prognosis. The recent discovery of several novel ROS receptor tyrosine kinase molecular alterations in ...non-small cell lung cancer (NSCLC) presents a therapeutic opportunity for the development of new targeted treatment strategies. Here, we report that the NSCLC-derived fusion CD74-ROS, which accounts for 30% of all ROS fusion kinases in NSCLC, is an active and oncogenic tyrosine kinase. We found that CD74-ROS-expressing cells were highly invasive in vitro and metastatic in vivo. Pharmacologic inhibition of CD74-ROS kinase activity reversed its transforming capacity by attenuating downstream signaling networks. Using quantitative phosphoproteomics, we uncovered a mechanism by which CD74-ROS activates a novel pathway driving cell invasion. Expression of CD74-ROS resulted in the phosphorylation of the extended synaptotagmin-like protein E-Syt1. Elimination of E-Syt1 expression drastically reduced invasiveness both in vitro and in vivo without modifying the oncogenic activity of CD74-ROS. Furthermore, expression of CD74-ROS in noninvasive NSCLC cell lines readily conferred invasive properties that paralleled the acquisition of E-Syt1 phosphorylation. Taken together, our findings indicate that E-Syt1 is a mediator of cancer cell invasion and molecularly define ROS fusion kinases as therapeutic targets in the treatment of NSCLC.
The
p53 tumor suppressor gene is commonly altered in human tumors, predominantly through missense mutations that result in accumulation of mutant p53 protein. These mutations may confer ...dominant-negative or gain-of-function properties to
p53. To ascertain the physiological effects of
p53 point mutation, the structural mutant
p53
R172H
and the contact mutant
p53
R270H
(codons 175 and 273 in humans) were engineered into the endogenous
p53 locus in mice.
p53
R270H/+
and
p53
R172H/+
mice are models of Li-Fraumeni Syndrome; they developed allele-specific tumor spectra distinct from
p53
+/− mice. In addition,
p53
R270H/
− and
p53
R172H/
− mice developed novel tumors compared to
p53
−/− mice, including a variety of carcinomas and more frequent endothelial tumors. Dominant effects that varied by allele and function were observed in primary cells derived from
p53
R270H/+
and
p53
R172H/+
mice. These results demonstrate that point mutant
p53 alleles expressed under physiological control have enhanced oncogenic potential beyond the simple loss of
p53 function.
Distinguishing aggressive from indolent disease and developing effective therapy for advanced disease are the major challenges in prostate cancer research. Chromosomal rearrangements involving ETS ...transcription factors, such as ERG and ETV1, occur frequently in prostate cancer. How they contribute to tumorigenesis and whether they play similar or distinct in vivo roles remain elusive. Here we show that in mice with ERG or ETV1 targeted to the endogenous Tmprss2 locus, either factor cooperated with loss of a single copy of Pten, leading to localized cancer, but only ETV1 appeared to support development of invasive adenocarcinoma under the background of full Pten loss. Mechanistic studies demonstrated that ERG and ETV1 control a common transcriptional network but largely in an opposing fashion. In particular, while ERG negatively regulates the androgen receptor (AR) transcriptional program, ETV1 cooperates with AR signaling by favoring activation of the AR transcriptional program. Furthermore, we found that ETV1 expression, but not that of ERG, promotes autonomous testosterone production. Last, we confirmed the association of an ETV1 expression signature with aggressive disease and poorer outcome in patient data. The distinct biology of ETV1-associated prostate cancer suggests that this disease class may require new therapies directed to underlying programs controlled by ETV1.
Neuronal loss and axonal degeneration are important pathological features of many neurodegenerative diseases. The molecular mechanisms underlying the majority of axonal degeneration conditions remain ...unknown. To better understand axonal degeneration, we studied a mouse mutant wabbler-lethal (wl). Wabbler-lethal (wl) mutant mice develop progressive ataxia with pronounced neurodegeneration in the central and peripheral nervous system. Previous studies have led to a debate as to whether myelinopathy or axonopathy is the primary cause of neurodegeneration observed in wl mice. Here we provide clear evidence that wabbler-lethal mutants develop an axonopathy, and that this axonopathy is modulated by Wld(s) and Bax mutations. In addition, we have identified the gene harboring the disease-causing mutations as Atp8a2. We studied three wl alleles and found that all result from mutations in the Atp8a2 gene. Our analysis shows that ATP8A2 possesses phosphatidylserine translocase activity and is involved in localization of phosphatidylserine to the inner leaflet of the plasma membrane. Atp8a2 is widely expressed in the brain, spinal cord, and retina. We assessed two of the mutant alleles of Atp8a2 and found they are both nonfunctional for the phosphatidylserine translocase activity. Thus, our data demonstrate for the first time that mutation of a mammalian phosphatidylserine translocase causes axon degeneration and neurodegenerative disease.
Oncoproteins and tumor suppressors antagonistically converge on critical nodes governing neoplastic growth, invasion, and metastasis. We discovered that phosphorylation of the ETS1 and ETS2 ...transcriptional oncoproteins at specific serine or threonine residues creates binding sites for the COP1 tumor suppressor protein, which is an ubiquitin ligase component, leading to their destruction. In the case of ETS1, however, phosphorylation of a neighboring tyrosine residue by Src family kinases disrupts COP1 binding, thereby stabilizing ETS1. Src-dependent accumulation of ETS1 in breast cancer cells promotes anchorage-independent growth in vitro and tumor growth in vivo. These findings expand the list of potential COP1 substrates to include proteins whose COP1-binding sites are subject to regulatory phosphorylation and provide insights into transformation by Src family kinases.
•ETS1 and ETS2 are substrates of the COP1 tumor suppressor ubiquitin ligase complex•Phosphorylation of specific Ser/Thr residues in ETS1 and ETS2 enables COP1 binding•Tyr phosphorylation of ETS1 by Src family kinases prevents COP1 binding•Src-induced accumulation of ETS1 promotes breast cancer growth in vitro and in vivo
Lu et al. show that the degradation of the ETS1 transcription factor mediated by the binding of ubiquitin ligase component COP1 is abolished when ETS1 is phosphorylated by Src family kinases (SFK) near the COP1 binding site. Phosphorylation of ETS by SFK leads to ETS1 accumulation to promote tumorigenesis.
L3mbtl2 has been implicated in transcriptional repression and chromatin compaction but its biological function has not been defined. Here we show that disruption of L3mbtl2 results in embryonic ...lethality with failure of gastrulation. This correlates with compromised proliferation and abnormal differentiation of L3mbtl2−/− embryonic stem (ES) cells. L3mbtl2 regulates genes by recruiting a Polycomb Repressive Complex1 (PRC1)-related complex, resembling the previously described E2F6-complex, and including G9A, Hdac1, and Ring1b. The presence of L3mbtl2 at target genes is associated with H3K9 dimethylation, low histone acetylation, and H2AK119 ubiquitination, but the latter is neither dependent on L3mbtl2 nor sufficient for repression. Genome-wide studies revealed that the L3mbtl2-dependent complex predominantly regulates genes not bound by canonical PRC1 and PRC2. However, some developmental regulators are repressed by the combined activity of all three complexes. Together, we have uncovered a highly selective, essential role for an atypical PRC1-family complex in ES cells and early development.
► The Polycomb group protein L3mbtl2 is essential for early embryonic development ► L3mbtl2 promotes ES cell proliferation and represses differentiation programs ► L3mbtl2 interacts with pluripotency factors and a non-canonical PRC1 complex ► L3mbtl2 represses regulators of endoderm, trophectoderm, and germ cell development
The chromatin protein L3mblt2 plays an essential role in early differentiation in vitro and in vivo through an atypical PRC1 complex and repressive histone modifications.
Cells that are deficient in homologous recombination, such as those that lack functional breast cancer-associated 1 (BRCA1) or BRCA2, are hypersensitive to inhibition of poly(ADP-ribose) polymerase ...(PARP). However, BRCA-deficient tumors represent only a small fraction of adult cancers, which might restrict the therapeutic utility of PARP inhibitor monotherapy. Cyclin-dependent kinase 1 (Cdk1) phosphorylates BRCA1, and this is essential for efficient formation of BRCA1 foci. Here we show that depletion or inhibition of Cdk1 compromises the ability of cells to repair DNA by homologous recombination. Combined inhibition of Cdk1 and PARP in BRCA-wild-type cancer cells resulted in reduced colony formation, delayed growth of human tumor xenografts and tumor regression with prolonged survival in a mouse model of lung adenocarcinoma. Inhibition of Cdk1 did not sensitize nontransformed cells or tissues to inhibition of PARP. Because reduced Cdk1 activity impaired BRCA1 function and consequently, repair by homologous recombination, inhibition of Cdk1 represents a plausible strategy for expanding the utility of PARP inhibitors to BRCA-proficient cancers.
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