Originally published in Chinese Journal of Oncology Clinical, 2021, 48(23): 1235-1238.
summary
Triple-negative breast cancer (TNBC) has the characteristics of high histological grading, late clinical stage, strong invasiveness, and easy metastasis. Due to the lack of effective therapeutic targets, traditional chemotherapy remains the mainstay of treatment for patients with TNBC. As a highly heterogeneous disease, TNBC requires more precise predictive biomarkers. The development of omics techniques and the implementation of clinical trials have brought new explorations to the prognostic biomarkers of adjuvant chemotherapy, covering different dimensions such as genes, proteins and microenvironment components, as well as the application of multi-molecule combined analysis. In this paper, we will review the prognostic biomarkers of TNBC adjuvant chemotherapy and their underlying molecular mechanisms and future development directions.
preface
Triple-negative breast cancer (TNBC) is a special molecular subtype of breast cancer (BC) with estrogen receptors (ER), progesterone receptors (PR) and human epidermal growth Factor receptor-2, HER-2) is negative and accounts for 10 to 15 percent of all BCs[1]. TNBC usually has a high histological grade, late clinical stage, biological behavior has the characteristics of strong invasiveness and easy metastasis, and lacks endocrine and anti-HER-2 targets, there is no targeted treatment plan, easy to resist and relapse, and poor prognosis. Adjuvant chemotherapy reduces the risk of recurrence and death of TNBC, but recurrence occurs in 20 to 40 percent of patients, and patients with TNBC who receive the same regimen in the same stage may have different clinical outcomes due to individual differences and tumor heterogeneity [2]. Prognostic biomarkers can help determine the clinical outcomes that may occur after a patient receives treatment, so effective prognostic indicators will provide a reference for TNBC treatment and improved prognosis. In this article, the prognostic biomarkers of TNBC adjuvant chemotherapy, their mechanisms of action and potential therapeutic value will be reviewed.
01 TNBC adjuvant chemotherapy regimen and its mechanism of action
TNBC is one of the factors considering adjuvant chemotherapy because it is a high risk of recurrence. At present, domestic and foreign guidelines and consensus suggest that anthracycline + cyclophosphamide sequential yew (AC-T/P), docetaxel + doxorubicin + cyclophosphamide (TAC), fluorouracil + epirubicin + cyclophosphamide sequential docetaxel (FEC-T), fluorouracil + doxorubicin + cyclophosphamide (FAC) and other anthracycline and taxosulos-based chemotherapy regimens are standard adjuvant treatment regimens [3]. In addition, capecitabine and platinum have also achieved significant results in TNBC adjuvant therapy, but adverse reactions have increased. Li et al. [4] studies have shown that standard anthracycline/yew chemotherapy regimens combined with capecitabine, i.e., docetaxel + capecitabine sequential capecitabine + epirubicin + cyclophosphamide (TX-XEC), improve the 5-year disease-free survival (DFS) rate in patients with early TNBC and reduce the risk of disease progression by 34%. Yuan et al. [5] studies have also affirmed the effect of low-dose capecitabine maintenance therapy after adjuvant chemotherapy. A phase III clinical trial suggests that platinum-plus yews have longer DFS than FEC-T regimens or may be a new option for adjuvant therapy [6]. Chemotherapy drugs mainly achieve anti-tumor purposes by directly killing tumor cells, among which anthracyclines, cyclophosphamides and platinums destroy the DNA double-stranded structure and belong to cycle-non-specific drugs; taxa inhibit microtubule depolymerization and act on mitosis M phase; capecitabine/fluorouracil interfere with nucleic acid synthesis, acting on S stage, and taxa and capecitabine/fluorouracil are cycle-specific drugs. Combination chemotherapy regimens should include more than two classes of drugs with different mechanisms of action, with cycle-specific nonspecific combination-specific agents, taking into account adverse effects.
02 Markers of gene and epigenetic prognosis
2.1 System homologous recombination to repair defects
Homologous recombination is a mechanism by which cells repair DNA double-strand breaks, and key components include BRCA1/2 and other Fanconi anemia pathway genes. Telli et al. [7] studies have shown that in patients with TNBC treated with doxorubicin or cyclophosphamide, a positive state (containing a pathogenic tBRCA1/2 mutation or HRD score≥ of 42) with homologous recombination deficiency (HRD) is associated with longer DFS (P=0.049). The study also found that in patients with negative tBRCA mutations, high HRD (score ≥42) also predicted better DFS (P=0.023) and overall survival [overall survival, OS, P=0.049]. HRD status can be used as a prognostic marker and is strongly associated with dna damage induced by chemotherapy drugs that cause cells to be unable to repair.
In HRD, epigenetics also play an important role in BRCA1 inactivation. BRCA1 resists apoptosis caused by DNA damage drugs, reduces drug sensitivity, and promoter methylation (PM) reduces mRNA and protein expression, enhancing drug efficacy [8]. A study of TNBC using anthracyclines as adjunctive therapy showed a significant increase in median DFS in PM patients with BRCA1 (P=0.001), and multivariate analysis showed that PM of BRCA1 was an independent prognostic factor affecting DFS (P=0.001) [9]. Jacot et al. [10] also confirmed that patients with high BRCA1 PM had a significantly improved prognosis after receiving adjuvant chemotherapy (P=0.024). The above results provide evidence that THE PM of BRCA1 is a prognostic marker of TNBC adjuvant chemotherapy. However, Sharma et al. [2] studies have shown that in PATIENTS with adjuvant chemotherapy BC, the PM of BRCA1 is associated with longer DFS and OS, but the difference is not statistically significant (P=0.25 and P=0.50), and these results may be related to sample size and patient population heterogeneity.
2.2 Polymorphism of the polyamorous ADP ribose polymerase 1 gene
PolyADP-riobsepolymerase (PARP) is a highly abundant and structurally conserved signaling protein that is critical for DNA single-strand break repair and is a pathway associated with base excision repair, with PARP1 primarily responsible for identifying damaged bases and recruiting repaired proteins [11]. An analysis of anthracycline/yew adjuvant chemotherapy regimens in patients with stage I to III TNBC showed that survival was significantly associated with PARP1 gene polymorphisms after adjusting for factors such as age, grade, tumor size, lymph node status, and vascular infiltration [12]. The study showed that the DFS of rs7531668 TA carriers was significantly higher than that of TT carriers, with 5-year DFS of 79.3% and 69.2% (P=0.046), respectively; in the lymph node-negative subgroup, the DFS of rs6664761 CC carriers was significantly higher than that of TT carriers (P=0.016), and the DFS of rs7531668 AA carriers was lower than that of TT carriers (P=0.015); in the ≤50-year subgroup, rs6664761 Patients with TC have better DFS than TT (P=0.042). The above results show that PARP1 gene polymorphisms have a predictive effect on DFS after anthracene/yew adjuvant chemotherapy regimens in patients with TNBC, especially for stratified analysis of clinical pathological features.
2.3 Genes associated with epithelial mesenchymal transformation
TNBC has strong ability to invade and transfer, and epithelial mesenchymal transition (EMT) is an important biological mechanism for metastasis. For metastatic TNBC, six gene signatures of EMT genes, including LUM, SFRP4, COL6A3, MMP2, CXCL12, and HTRA1, were identified by gene collection and enrichment analysis, which were consistently highly expressed in metastatic TNBC and had predictive value for metastasis in patients with tNBC undergoing adjuvant chemotherapy (P=0.032) [13]. Therefore, the above EMT gene analysis can suggest the metastatic potential of TNBC after surgery combined with adjuvant chemotherapy to monitor TNBC progression.
03 Protein molecules expressed by tumor cells
3.1 B lymphocytoma-2
Excessive activation of the apoptotic regulatory protein B-cell lymphoma-2 (BCL-2) can affect the development of tumors, chemoradiotherapy resistance, and disease outcome. In 70% of early TNBCs, BCL-2 deletion (BCL-2-) was significantly associated with strong tumor proliferation and increased expression of CK19, P-calciumin, E-calcinixin, and HER-3 (P<0.01), and positive BCL-2 (BCL-2+) was significantly associated with high expression of p27, MDM4, and SPAG5 (P <0.01）。 In patients with early TNBC with BCL-2-, anthracycline adjuvant chemotherapy increased both BC-specific survival (P=0.002) and DFS (P=0.003) compared with no chemotherapy or cyclophosphamide+methotrexate+fluorouracil (CMF) regimens [14]. However, Tawfik et al. [15] found that TNBC with BCL-2+ had a worse prognosis than a negative one, and the reason for the difference may be related to sample size and treatment options. Whether BCL-2 can be used in clinical practice as a prognostic marker is still controversial.
3.2 Fork head box protein C1
Forkhead box protein C1 (FOXC1) is a member of the forkhead box transcription factor superfamily that plays an important role in cell growth, survival, differentiation, and migration, and overexpression and silencing FOXC1 in BC cells induces and inhibits invasion phenotypes. Patients with relapsed and/or metastatic TNBC were found to have a higher rate of FOXC1 overexpression than in the control group (P<0.05), and foxc1 expression patients with poor DFS (P=0.038) in patients undergoing anthracycline chemotherapy regimens, but were not associated with OS [16]. Therefore, FOXC1 may be associated with anthracycline chemotherapy sensitivity and can be used as a potential biomarker for TNBC chemotherapy regimen selection and prognosis.
3.3 Cytochrome P450 reductase
Cytochrome P450 reductase (CYPOR) is an endoplasmic reticulum-associated flavin protein whose function involves enzyme composition and steroid and drug metabolism, so most of the related tumor research focuses on the metabolic effects of anti-cancer drugs such as doxorubicin, mitomycin C and PR-104A. In one proteomics study, higher CYPOR expression was found in metastatic patients by analyzing TNBC lesions (P=0.026) [17]. For further validation, Pedersen et al. [18] found that the relapse-free survival (RFS) of patients with high CYPOR expression was significantly shortened (P=0.018) in the inclusion of TNBC and was confirmed in the cohort of basal-like BC (P=0.018). The study also analyzed the cohort of enrolled Danish patients with TNBC and found that high CYPOR expression was associated with shorter RFS (P=0.017), particularly in the lymph node-negative group (P=0.029), and the multivariate analysis of the Cox proportional risk regression model suggested that CYPOR was an independent prognostic factor for RFS shortening in patients with TNBC (P=0.032). CYPOR high expression predicts RFS shortening and identifies patients who require active adjuvant therapy and monitoring.
04 Prognostic markers in the tumor microenvironment
There is a complex interaction between tumors and the body's immune system, namely immune editing, which is mainly mediated by CD8+ T cells and involves a variety of immunostimulators and suppressors. BC is a non-immunogenic disease with a relatively low mutation rate, while TNBC has a high mutation rate and tumor-infiltrating lymphocytes (TILs) are more. Currently, TNBC immune-related markers for prognosis show predictive potential and provide a reference for clinical applications.
4.1 Immune-related genes
Based on gene expression profiling, Lehmann et al. [19] divided TNBC into six different subtypes: basal sample (BL) 1 and 2, immunomodulatory (IM), mesenchymal (M), mesenchymal stem cells (MSL), and luminal/androgen receptor (LAR). A high-risk BC study of adjuvant chemotherapy showed that IM-type DFS was optimal, enriching multiple genes involved in immune regulation, involving immune cell signal transduction, antigen processing, and expression [20]. The study showed through cluster analysis that TNBC with T cell activation characteristics showed better DFS after adjuvant chemotherapy (P=0.04). At the same time, T cell-mediated cytotoxicity-related genes (such as GZMA, PRF1, PDL2, and CD8A) predict longer DFS; conversely, the expression of five other immune-related genes (B7H3, CD24, CD29, IL8, and LY6E) predicts shorter DFS. Asleh et al. [21] Using TNBC tissues in FinXX clinical trials, 770 genes and 30 genes associated with capecitabine metabolic pathways involved in multiple biological mechanisms were analyzed and found that genes related to anti-tumor immunity, immune response, and activation of capecitabine metabolic enzymes, including cytotoxic cell, endothelial and mast cell gene markers, and programmed death-ligand 2 (PD-L2), The RFS of patients was significantly improved, and the difference was statistically significant (P=0.01, P=0.02, P=0.04, and P=0.03). These predictive genes may screen out patients with TNBC who are more likely to benefit from capecitabine-assisted therapy.
4.2 Procedural death ligand 1
Programmed death-ligand 1 (PD-L1) is primarily involved in the negative regulation of T cell function and is expressed in a variety of tumor cells (TCs) and immune cells (IC). PD-L1 is associated with some aggressive features in BC, such as young, high-grade, and Luminal-negative/HER-2 positive, TNBC, basal-like, and HER-2 enriched subtypes, but high expression of PD-L1 still shows chemotherapy sensitivity and better OS, indicating an interaction between immune response and antitumor activity. IMpassion 130 studies have shown that 1% of patients with PD-L1-positive IC ≥ use albumin-binding paclitaxel combined with atezolizumab as a first-line treatment, and OS can be extended by 7 months (25 months vs. 18 months)[22], suggesting that PD-L1 has predictive value. However, due to the influence of the sample and time, the positive TC and IC test results are different and the stability is not clear due to the influence of the sample and the time.
4.3 TILs
TILs are present in intratumoral and paratumorous interstitial tissues, mainly composed of CD8+ cytotoxic T cells, and there are also few cd4+ helper T cells, Treg, macrophages, mast cells and plasma cells. More than 50 to 60 percent of tumors are TILs, which are defined as lymphocyte predominant breast cancer (LPBC), with a better prognosis of LPBC in TNBC [23]. Loi et al. [24] studies have shown that in ER-negative/HER-2-negative BC, interstitial TILs increase by 10%, the risk of recurrence is reduced by 15% (P=0.025), and the risk of death is reduced by 17% (P=0.023), regardless of the chemotherapy regimen. Another study showed a 10 percent increase in TNBC interstitial TILs, a 14 percent lower risk of recurrence or death (P=0.02), a 18 percent lower risk of distant metastases (P=0.04), and a 19 percent lower risk of death (P=0.01) [25]. TILs have been widely recognized as markers of TNBC prognosis, and the Saint Gallen Consensus (2019) recommends routine clinical use.
05
epilogue
The ideal prognostic biomarker for TNBC-assisted chemotherapy is similar to other markers. It should also have the following characteristics: high validity, can more accurately predict the prognosis of TNBC adjuvant chemotherapy, good reliability, less interfered with by other clinical pathological factors, strong specificity, targeted prediction results, easy to use, such as present in body fluids, conducive to popularization, can predict short-term drug treatment response, provide a reference for TNBC patient management, has potential therapeutic value, provides clues for drug development, and develops in the direction of multiomics, making full use of emerging biomedical technologies. At the same time, large-scale prospective clinical studies are still needed to verify them because prognostic biomarkers need to be ruled out by other factors.
End
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Cite this article:
GUO Fengzhu, LI Zhijun, XU Binghe. Research Progress on Prognostic Biomarkers of Adjuvant Chemotherapy for Triple-Negative Breast Cancer[J]. Chinese Journal of Clinical Oncology, 2021, 48(23): 1235-1238. doi: 10.12354/j.issn.1000-8179.2021.20211156