Epithelial/Mesenchymal Characteristics and PD-L1 Co-Expression in CTCs of Metastatic Breast Cancer Patients Treated with Eribulin: Correlation with Clinical Outcome

Abstract

We aimed to evaluate the co-expression of PD-L1 and epithelial-mesenchymal markers in CTCs from metastatic breast cancer (MBC) patients and to determine if there is any relationship with patients’ outcome after eribulin treatment. Using cytospin preparations of peripheral blood mononuclear cells (PBMCs) from MBC patients treated with eribulin and a combination of immunocytochemistry and immunofluorescence, we quantified PD-L1, keratins and vimentin in single and cluster CTCs on days 1 and 8 of the first-treatment cycle. CTCs (n = 173) were found in 31 out of 38 patients. At baseline, the presence of cluster CTCs (p = 0.048), cluster mesenchymal CTCs (mCTCs) (p = 0.0003) or cluster PD-L1+mCTCs (p = 0.006) was associated with shorter overall survival (OS). In multivariate cox regression analysis, the detection of cluster mCTCs was the only parameter associated with increased risk of death (p = 0.024). On day 8 post-eribulin administration, PD-L1+mCTCs and especially single PD-L1+mCTCs decreased in 75% and 89% of patients, respectively. The detection of single PD-L1+mCTCs after eribulin treatment was correlated with shorter PFS (p = 0.047) and OS (p = 0.020). In conclusion, our study identified for the first time that cluster and single PD-L1+mCTCs subpopulations are of clinical significance in patients with MBC and highlighted the importance of CTC phenotyping during treatment with eribulin.

Prognostic significance of programmed cell death‐ligand 1 expression on circulating tumor cells in various cancers: A systematic review and meta‐analysis

“…Furtherly, we excluded five candidate studies for the following reasons: one only provided specimen‐level survival data, 29 one reported the correlation of PD‐L1 + CTCs/circulating immune cells with survival, 30 one was duplicated with another study, 18 , 31 and two did not report survival outcomes. 32 , 33 Finally, we identified 30 studies eligible for the present meta‐analysis 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 as shown in Figure 1 . A total of 1419 patients with malignant tumors, including 208 breast cancer, 253 gastrointestinal cancer, 194 genitourinary cancer, 161 head and neck cancer, 25 melanoma, 12 metastatic neuroendocrine tumor, and 566 NSCLC, were analyzed.…”

“…Previous studies found that CTCs undergoing epithelial‐to‐mesenchymal transition (EMT) were associated with invasion and metastasis and had increased expression of mesenchymal markers such as CSV. 54 Subgroup analysis involving five cohorts of patients 22 , 24 , 34 , 45 showed that patients with CSV + PD‐L1 + CTCs had markedly worse PFS (HR = 2.47, 95% CI 1.41–4.33) and OS (HR = 3.46, 95% CI 2.13–5.61).…”

“…If so, there should be a correlation between the effect size, that is, HR, of both markers. We included seven studies that reported the associations of both markers with PFS 22 , 24 , 34 , 38 , 42 , 49 and OS. 22 , 24 , 34 , 37 , 38 , 42 Meta‐regression analysis showed that HRs for CTCs did not modify the effect sizes of PD‐L1 + CTCs with PFS and OS ( p = 0.870 and 0.410, respectively).…”

“…Furtherly, we excluded five candidate studies for the following reasons: one only provided specimen-level survival data, 29 one reported the correlation of PD-L1 + CTCs/circulating immune cells with survival, 30 one was duplicated with another study, 18,31 and two did not report survival outcomes. 32,33 Finally, we identified 30 studies eligible for the present meta-analysis [18][19][20][21][22][23][24][25][26][27][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53] as shown in Figure 1…”

Currently Used Laboratory Methodologies for Assays Detecting PD-1, PD-L1, PD-L2 and Soluble PD-L1 in Patients with Metastatic Breast Cancer

“…Moreover, diverse methods have been utilized for the enrichment and detection of circulating tumor cells [107,108]. The developed techniques demonstrated high sensitivity and facilitated the quantification of these cells [109,110]. However, analyses of images can be subjective, and therefore, data should be interpreted with caution because of the high background fluorescence related to this methodology.…”