SARS-CoV-2 receptor ACE2 identifies immuno-hot tumors in breast cancer
Summary (2 min read)
Introduction
- Coronavirus disease 2019 (COVID-19) is infectious pneumonia caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection [1].
- Thus, organs expressing high ACE2 appear to be more impressionable to SARS-CoV-2 infection in healthy individuals.
- Cold tumors are characterized as immunosuppressive TME and insensitive to either chemotherapy or immunotherapy, and hot tumors represent higher response rates to these therapies, which is featured by T cell infiltration and immunosuppressive TME [14].
- The authors discovered that ACE2 exhibited the tightest correlation with immunological factors in BRCA, which may be a dominant tumor species for the in-depth analysis of the immunological role of ACE2.
Public datasets retrieval
- The pan-cancer normalized RNA-seq datasets, copy number variant (CNV) data processed by GISTIC algorithm, 450K methylation data, mutation profiles, the activities of transcription factor (TF) calculated by RABIT, and clinical information were obtained from UCSC Xena data portal (https://xenabrowser.net/datapages/).
- Prognostic analysis using PrognoScan PrognoScan database (http://dna00.bio.kyutech.ac.jp/PrognoScan/) was applied to assess the prognostic value of ACE2 in BRCA across a large cohort of public microarray datasets [17].
- All the results were exhibited in the study.
- ESTIMATE algorithm was also performed to calculate Tumor Purity, ESTIMATE Score, Immune Score and Stromal Score [26].
- Furthermore, the authors also collected several well-known effector genes of TIICs, and computed the T cell inflamed score according to the expression levels and weighting coefficient of 18 genes reported by Ayer et al. [27].
Immunophenoscore analysis
- As previously reported, a patient’s immunophenoscore (IPS) can be calculated without bias using machine learning by consideration of the 4 major categories of components that measure immunogenicity: effector cells, immunosuppressive cells, MHC molecules, and immunomodulators [19].
- The IPS values of BRCA patients were obtained from the Cancer Immunome Atlas (TCIA) (https://tcia.at/home).
- Calculation of the enrichment scores of various gene signatures According to previous research [28], the authors collected several gene-sets positively associated with therapeutic response to immunotherapy, targeted therapy and radiotherapy, and specific markers of biological process correlated with anti-tumor immunity such as genes involved in DNA replication.
- The enrichment scores of these signatures were obtained using the GSVA R package [29].
Prediction of therapeutic response
- The role of ACE in predicting the response to chemotherapy was also evaluated.
- First, BRCA-related drug-target genes were screened using the Drugbank database (https://go.drugbank.com/).
- Several common therapeutics, including vinblastine, cisplatin, doxorubicin, etoposide, gefitinib, gemcitabine, paclitaxel, parthenolide, sunitinib and vinorelbine were selected.
- The prediction process was performed by R package “pRRophetic” where the samples’ half-maximal inhibitory concentration (IC50) was calculated by ridge regression and the prediction accuracy was assessed by 10-fold cross-validation according to the CGP training set.
- Default options were used for all parameters [30].
Clinical samples
- Two tissue microarrays (TMAs, HBreD050Bc01 and HBreD090Bc03) were obtained from Outdo Biotech (Shanghai, China).
- The HBreD050Bc01 microarray contained 40 BRCA and 10 adjacent samples.
- The HBreD090Bc03 microarray contained 85 BRCA and 5 adjacent samples.
- Thus, a total of 125 BRCA samples and 15 adjacent samples were involved in the current research.
Immunohistochemistry and semi-quantitative evaluation
- Next, Immunohistochemistry (IHC) staining was conducted on these tissue slides.
- Antibody staining was visualized with DAB and hematoxylin counterstain, and stained sections were scanned using Aperio Digital Pathology Slide Scanners.
- All stained sections were independently evaluated by two independent pathologists.
- The immunoreactivity score (IRS) equals to the percentages of positive cells multiplied with staining intensity.
Statistical analysis
- Statistical analysis and figure exhibition performed using R language 4.0.0.
- The statistical difference of continuous variables between the two groups was evaluated by Wilcoxon rank sum test or Mann-Whitney test and chi-square test was used when the categorical variables were assessed.
- Pearson’s correlation was used to evaluete the correlation between two variables.
- Receiver-operating characteristic (ROC) analysis was plotted to assess the specificity and sensitivity of the candidate indicator, and the area under the ROC curve (AUC) was generated for diagnostic biomarkers.
- Prognostic values of categorical variables were assessed by log-rank test.
Results
- Expression and immunological roles of ACE2 across human cancers.
- In their research, ACE2 was suggested to be positively related to most immune checkpoints, including VTCN1, PD-L1, PD-1, CTLA4 and so on .
- As Figure 4A exhibited, ACE2 expression was significantly associated with age, histological type, molecular type, ER status and PR status, but not related to other features.
- To further validate above results, the authors also obtained a TMA cohort for verification, which included 125 BRCA samples and 15 adjacent samples.
- In conclusion, ACE2 expression is related to clinical features and immune phenotypes in BRCA.
Discussion
- COVID-19 is becoming a global concern and the major public threat in the last two years.
- Besides, cancer patients have a worse prognosis after SARS-CoV-2 infection.
- Thus, the authors speculated SARS‐CoV‐2 infection induced spontaneous remission of tumor has parallels with oncolytic virotherapy to some extent.
- Besides, the associations between ACE2 with anti-tumor immunity and immunotherapy were also explored.
- PD-L1 was often overexpressed in TNBC [46], and its response to immune checkpoint inhibition was encouraging.
Conclusions
- In the current study, the authors revealed that ACE2 shaped an inflamed TME according to the evidence that ACE2 positively related to the immunological patterns of TME in BRCA.
- Besides, the authors uncovered that BRCA had the potential to estimate the response of immunotherapy, the molecular subtypes and the response to several therapeutic strategies.
- Overall, ACE2 may be used as a promising biomarker for the identification of immunological features in BRCA.
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Frequently Asked Questions (14)
Q2. What is the significance of ACE2 in the pan-cancer analysis?
After a systematic pan-cancer analysis of the expression of ACE2 in the TCGA database, the authors discovered that ACE2 was lowly expressed in a fraction of cancers, including BRCA, KICH, and LUAD.
Q3. What is the significance of the isolated case report?
an isolated case report has revealed that SARS-CoV-2 infection inducedcomplete spontaneous remission in a patient with lymphoma [42].
Q4. What is the role of ACE2 in identifying an inflamed TME?
ACE2 is tightly correlated with the development of an inflamed TME, which may act as a critical role in identifying the immunogenicity of BRCA.
Q5. What are the main components of the tumor microenvironment?
Themultiple interplays between these cells via cytokines, chemokines and growth factors constitute the tumor microenvironment (TME) [13].
Q6. What is the significance of ACE2 in the diagnosis of BRCA?
In their research, ACE2 was suggested to be positively related to most immune checkpoints, including VTCN1, PD-L1, PD-1, CTLA4 and so on (Figure 2F).
Q7. What were the top 5 terms positively correlated with ACE2 expression of each analysis?
Plentiful of statistically significant terms were found and the top 5 terms positively correlated with ACE2 expression of each analysis were retained.
Q8. What is the prognostic value of ACE2 in BRCA?
The authors speculated that the prognostic value of ACE2 may be associated with subtypes and therapeutic regimens in BRCA, which needed to be further studied.
Q9. What is the significance of the ACE2 expression in BRCA?
according to previous research, ACE2 was not expressed in immune cells, and the expression of ACE2 in bulk RNA-seq data was derived from non-immune cells in all probability, such as tumor cells in the tissues.[31]
Q10. What is the ACE2 biomarker for predicting the response to PD-1?
T cell inflamed score is developed using IFN-γ-related mRNA profiles to predict clinical response to PD-1 blockade [27], and BRCA patients in the high ACE2 group exhibited higher T cell inflamed scores (Figure 3B).
Q11. What is the significance of ACE2 in breast cancer?
ACE2 was upregulated in ER-negative, PR-negative and the triple-negative breast cancer (TNBC) tissues (Figure S5A), and ROC analysis indicated a notable diagnostic value in identifying these molecular subtypes (Figure S5B).
Q12. What is the significance of ACE2 in BRCA?
targeted therapy suppressing these oncogenic pathways could be applied for the treatment of BRCA with high ACE2 expression.
Q13. What is the significance of IPS in BRCA?
Using IPS as a surrogate of the response to immunotherapy, the authors discovered that patients with high ACE2 expression had notably higher IPS (Figure 3G).
Q14. In what studies did Yang et al. report that ACE2 was associated with enhanced?
Yang et al. [12] reported that the overexpression of ACE2 was significantly associated with enhanced immune infiltration in endometrial cancer and renal papillary cell cancer.