Many tumours are composed of genetically diverse cells; however, little is known about how diversity evolves or the impact that diversity has on functional properties. Here, using xenografting and ...DNA copy number alteration (CNA) profiling of human BCR-ABL1 lymphoblastic leukaemia, we demonstrate that genetic diversity occurs in functionally defined leukaemia-initiating cells and that many diagnostic patient samples contain multiple genetically distinct leukaemia-initiating cell subclones. Reconstructing the subclonal genetic ancestry of several samples by CNA profiling demonstrated a branching multi-clonal evolution model of leukaemogenesis, rather than linear succession. For some patient samples, the predominant diagnostic clone repopulated xenografts, whereas in others it was outcompeted by minor subclones. Reconstitution with the predominant diagnosis clone was associated with more aggressive growth properties in xenografts, deletion of CDKN2A and CDKN2B, and a trend towards poorer patient outcome. Our findings link clonal diversity with leukaemia-initiating-cell function and underscore the importance of developing therapies that eradicate all intratumoral subclones.
To describe the clinical, pathological and genomic characteristics of pancreatic cancer with DNA mismatch repair deficiency (MMRD) and proficiency (MMRP).
We identified patients with MMRD and MMRP ...pancreatic cancer in a clinical cohort (N=1213, 519 with genetic testing, 53 with immunohistochemistry (IHC)) and a genomic cohort (N=288 with whole-genome sequencing (WGS)).
12 out of 1213 (1.0%) in the clinical cohort were MMRD by IHC or WGS. Of the 14 patients with Lynch syndrome, 3 (21.4%) had an MMRP pancreatic cancer by IHC, and 4 (28.6%) were excluded because tissue was unavailable for testing. MMRD cancers had longer overall survival after surgery (weighted HR after coarsened exact matching 0.11, 95% CI 0.02 to 0.78, p=0.001). One patient with an unresectable MMRD cancer has an ongoing partial response 3 years after starting treatment with PD-L1/CTLA-4 inhibition. This tumour showed none of the classical histopathological features of MMRD. 9 out of 288 (3.1%) tumours with WGS were MMRD. Despite markedly higher tumour mutational burden and neoantigen loads, MMRD cancers were significantly less likely to have mutations in usual pancreatic cancer driver genes like
and
, but more likely to have mutations in genes that drive cancers with microsatellite instability like
and
. MMRD tumours were significantly more likely to have a basal-like transcriptional programme and elevated transcriptional markers of immunogenicity.
MMRD pancreatic cancers have distinct clinical, pathological and genomic profiles. Patients with MMRD pancreatic cancer should be considered for basket trials targeting enhanced immunogenicity or the unique genomic drivers in these malignancies.
The molecular drivers of antitumor immunity in pancreatic ductal adenocarcinoma (PDAC) are poorly understood, posing a major obstacle for the identification of patients potentially amenable for ...immune-checkpoint blockade or other novel strategies. Here, we explore the association of chemokine expression with effector T-cell infiltration in PDAC.
Discovery cohorts comprised 113 primary resected PDAC and 107 PDAC liver metastases. Validation cohorts comprised 182 PDAC from The Cancer Genome Atlas and 92 PDACs from the Australian International Cancer Genome Consortium. We explored associations between immune cell counts by immunohistochemistry, chemokine expression, and transcriptional hallmarks of antitumor immunity by RNA sequencing (RNA-seq), and mutational burden by whole-genome sequencing.
Among all known human chemokines, a coregulated set of four (
, and
) was strongly associated with CD8
T-cell infiltration (
< 0.001). Expression of this "4-chemokine signature" positively correlated with transcriptional metrics of T-cell activation (
, and
), cytolytic activity (
and
), and immunosuppression (
, and
). Furthermore, the 4-chemokine signature marked tumors with increased T-cell activation scores (MHC I presentation, T-cell/APC costimulation) and elevated expression of innate immune sensing pathways involved in T-cell priming (STING and NLRP3 inflammasome pathways, BATF3-driven dendritic cells). Importantly, expression of this 4-chemokine signature was consistently indicative of a T-cell-inflamed phenotype across primary PDAC and PDAC liver metastases.
A conserved 4-chemokine signature marks resectable and metastatic PDAC tumors with an active antitumor phenotype. This could have implications for the appropriate selection of PDAC patients in immunotherapy trials.
Complex 3D bioengineered tumour models provide the opportunity to better capture the heterogeneity of patient tumours. Patient-derived organoids are emerging as a useful tool to study tumour ...heterogeneity and variation in patient responses. Organoid cultures typically require a 3D microenvironment that can be manufactured easily to facilitate screening. Here we set out to create a high-throughput, “off-the-shelf” platform which permits the generation of organoid-containing engineered microtissues for standard phenotypic bioassays and image-based readings. To achieve this, we developed the Scaffold-supported Platform for Organoid-based Tissues (SPOT) platform. SPOT is a 3D gel-embedded in vitro platform that can be produced in a 96- or 384-well plate format and enables the generation of flat, thin, and dimensionally-defined microgels. SPOT has high potential for adoption due to its reproducible manufacturing methodology, compatibility with existing instrumentation, and reduced within-sample and between-sample variation, which can pose challenges to both data analysis and interpretation. Using SPOT, we generate cultures from patient derived pancreatic ductal adenocarcinoma organoids and assess the cellular response to standard-of-care chemotherapeutic compounds, demonstrating our platform's usability for drug screening. We envision 96/384-SPOT will provide a useful tool to assess drug sensitivity of patient-derived organoids and easily integrate into the drug discovery pipeline.
Modified FOLFIRINOX (mFFX) and gemcitabine/nab-paclitaxel (GnP) remain standard first-line options for patients with advanced pancreatic ductal adenocarcinoma (PDAC). Human equilibrative nucleoside ...transporter 1 (hENT1) was hypothesized to be a biomarker of gemcitabine in the adjuvant setting, with conflicting results. In this study, we explore hENT1 mRNA expression as a predictive biomarker in advanced PDAC.
COMPASS was a prospective observational trial of patients with advanced PDAC. A biopsy was required prior to initiating chemotherapy, as determined by treating physician. Biopsies underwent laser capture microdissection prior to whole genome and RNA sequencing. The cut-off thresholds for hENT1 expression were determined using the maximal χ2 statistic.
253 patients were included in the analyses with a median follow-up of 32 months, with 138 patients receiving mFFX and 92 receiving GnP. In the intention to treat population, median overall survival (OS) was 10.0 months in hENT1high versus 7.9 months in hENT1low (P = 0.02). In patients receiving mFFX, there was no difference in overall response rate (ORR; 35% vs. 28%, P = 0.56) or median OS (10.6 vs. 10.5 months, P = 0.45). However, in patients treated with GnP, the ORR was significantly higher in hENT1high compared with hENT1low tumors (43% vs. 21%, P = 0.038). Median OS in this GnP-treated cohort was 10.6 months in hENT1high versus 6.7 months hENT1low (P < 0.001). In an interaction analysis, hENT1 was predictive of treatment response to GnP (interaction P = 0.002).
In advanced PDAC, hENT1 mRNA expression predicts ORR and OS in patients receiving GnP.
GATA6 is a key regulator of the classical phenotype in pancreatic ductal adenocarcinoma (PDAC). Low GATA6 expression associates with poor patient outcome.
is the second most expressed GATA factor in ...the pancreas. We assessed whether, and how, GATA4 contributes to PDAC phenotype and analysed the association of expression with outcome and response to chemotherapy.
We analysed PDAC transcriptomic data, stratifying cases according to
and
expression and identified differentially expressed genes and pathways. The genome-wide distribution of GATA4 was assessed, as well as the effects of
knockdown. A multicentre tissue microarray study to assess GATA4 and GATA6 expression in samples (n=745) from patients with resectable was performed. GATA4 and GATA6 levels were dichotomised into high/low categorical variables; association with outcome was assessed using univariable and multivariable Cox regression models.
messenger RNA is enriched in classical, compared with basal-like tumours. We classified samples in 4 groups as high/low for
and
. Reduced expression of
had a minor transcriptional impact but low expression of
enhanced the effects of
low expression. GATA4 and GATA6 display a partially overlapping genome-wide distribution, mainly at promoters. Reduced expression of both proteins in tumours was associated with the worst patient survival.
and
expression significantly decreased in metastases and negatively correlated with basal markers.
and
cooperate to maintain the classical phenotype. Our findings provide compelling rationale to assess their expression as biomarkers of poor prognosis and therapeutic response.
The majority of pancreatic ductal adenocarcinomas (PDACs) harbour oncogenic mutations in
with variants in
,
and
also prevalent. The presence of oncogenic fusions including
fusions are rare but ...important to identify. Here we ascertain the prevalence of
fusions and document their genomic characteristics in a large series of PDAC.
Whole genome sequencing and RNAseq were performed on a series of patients with resected or locally advanced/metastatic PDAC collected between 2008 and 2020 at a single institution. A subset of specimens underwent immunohistochemistry (IHC) analysis. Clinical and molecular characterisation and IHC sensitivity and specificity were evaluated.
400 patients were included (resected n=167; locally advanced/metastatic n=233). Three patients were identified as harbouring an
fusion, two
(
-WT) and a single novel
fusion. The latter occurring in the presence of a subclonal
mutation. Typical PDAC drivers were present including mutations in
and
. Substitution base signatures and tumour mutational burden were similar to typical PDAC. The prevalence of
fusions was 0.8% (3/400), while in
wild-type tumours, it was 6.25% (2/32). DNA prediction alone documented six false-positive cases. RNA analysis correctly identified the in-frame fusion transcripts. IHC analysis was negative in the
fusion but positive in a
case, highlighting lower sensitivity of IHC.
fusions are rare; however, with emerging therapeutic options targeting these fusions, detection is vital. Reflex testing for
mutations and subsequent RNA-based screening could help identify these cases in PDAC.
Pancreatic ductal adenocarcinoma (PDA), with its highly metastatic propensity, is one of the most lethal subtypes of pancreatic cancer. Although recent large-scale transcriptomic studies have ...demonstrated that heterogeneous gene expressions play an essential role in determining molecular phenotypes of PDA, biological cues for and consequences of distinct transcriptional programs remain unclear.
We developed an experimental model that enforces the transition of PDA cells toward a basal-like subtype. We combined epigenome and transcriptome analyses with extensive in vitro and in vivo evaluations of tumorigenicity to demonstrate the validity of basal-like subtype differentiation in association with endothelial-like enhancer landscapes via TEA domain transcription factor 2 (TEAD2). Finally, we used loss-of-function experiments to investigate the importance of TEAD2 in regulating reprogrammed enhancer landscape and metastasis in basal-like PDA cells.
Aggressive characteristics of the basal-like subtype are faithfully recapitulated in vitro and in vivo, demonstrating the physiological relevance of our model. Further, we showed that basal-like subtype PDA cells acquire a TEAD2-dependent proangiogenic enhancer landscape. Genetic and pharmacologic inhibitions of TEAD2 in basal-like subtype PDA cells impair their proangiogenic phenotypes in vitro and cancer progression in vivo. Last, we identify CD109 as a critical TEAD2 downstream mediator that maintains constitutively activated JAK-STAT signaling in basal-like PDA cells and tumors.
Our findings implicate a TEAD2-CD109-JAK/STAT axis in the basal-like differentiated pancreatic cancer cells and as a potential therapeutic vulnerability.
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TEAD2 expression is increased in basal-like pancreatic cancer cells and activates endothelial-like enhancers. Hence, inhibition of TEAD2 activity is sufficient to repress basal-like subtype differentiation and its associated phenotypes.
Introduction: Much of our fundamental understanding of stem cell biology comes from studies of hematopoiesis where single cells produce differentiated progeny while still retaining the ability to ...produce daughter stem cells (self-renewal). The cardinal property of a stem cell, whether normal or malignant, is self-renewal; the key biological process that ensures the ability of the stem cell to maintain long-term clonal growth. However, our understanding of the molecular basis of self-renewal in human hematopoiesis is limited.
At the embryonic stage fetal liver is the main source of hematopoiesis; from week 6 of gestation until before birth. At this stage HSCs are in a different microenvironment but capable of self-renewing and differentiation to the full spectrum of blood lineages. While murine studies uncovered several intrinsic differences between fetal and adult HSCs, a comprehensive analysis of human HSC compartment across development is lacking.
In this study we have combined HSC purification methods and xenograft quantitative assay in conjunction with low input RNA sequencing and Enhanced Reduced Representation Bisulfite Sequencing (ERRBS) to provide a comprehensive functional and molecular outlook of human stem cell compartment across development.
Results: We followed the dynamics of four sub-fractions of CD34+CD38- divided by CD90 and CD49f expression across human blood development: fetal liver (hFL) and adult bone marrow (hBM). Using xenograft model, we identified human long, intermediate and short term HSCs in hFL and hBM. 5 single CD90+CD49f+ hFL cells were capable of sustaining the multilineage graft for over 52 weeks up to tertiary recipient, while BM cells only last for 20 weeks in the primary recipient. The frequency of LT-HSC in the CD90+CD49f+ compartment goes from 1/8 in hFL to 1/50 in hBM. hFL CD90-CD49f+ cells showed an intermediate repopulation capacity up to 44 weeks in secondary recipient.
On average 10% of hFL long term HSC (LT-HSC) were in S/G2/M phase, in contrast only 0.4% of BM LT-HSC were in S/G2/M phase indicating that hFL HSCs are 20 times more in cycle compare to BM.
We found that 320 genes were expressed differentially between LT-HSC and multipotent progenitors (MPP) in hBM as oppose to only 32 genes found to be differentially expressed in hFL (FDR<0.1). Interestingly, we found only 2 genes in common between these two groups.
ERRBS showed an overall increase in methylation of HSC compartment in hBM compare to hFL and gradual demethylation of lineage associated genes in MPP.
Conclusion: Our data indicate that there are distinct regulatory networks that govern hFL and hBM HSC self-renewal. We found very little differences in gene expression between all hFL HCS compartments (average 20 genes) compare to hBM (average 224), indicating that by adulthood self-renewal is becoming more restricted to the LT-HSC compartment.
No relevant conflicts of interest to declare.
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