Utility of patient-derived lymphoblastoid cell lines as an ex vivo capecitabine sensitivity prediction model for breast cancer patients

Abstract

Capecitabine is commonly used in treating breast cancer; however, therapeutic response varies among patients and there is no clinically validated model to predict individual outcomes. Here, we investigated whether drug sensitivity quantified in ex vivo patients' blood-derived cell lines can predict response to capecitabine in vivo. Lymphoblastoid cell lines (LCLs) were established from a cohort of metastatic breast cancer patients (n = 53) who were prospectively monitored during treatment with single agent capecitabine at 2000 mg/m2/day. LCLs were treated with increasing concentrations of 5'-DFUR, a major capecitabine metabolite, to assess patients' ex vivo sensitivity to this drug. Subsequently, ex vivo phenotype was compared to observed patient disease response and drug induced-toxicities. We acquired an independent cohort of breast cancer cell lines and LCLs derived from the same donors from ATCC, compared their sensitivity to 5'-DFUR. As seen in the patient population, we observed large inter-individual variability in response to 5'-DFUR treatment in patient-derived LCLs. Patients whose LCLs were more sensitive to 5'-DFUR had a significantly longer median progression free survival (9-month vs 6-month, log rank p-value = 0.017). In addition, this significant positive correlation for 5'-DFUR sensitivity was replicated in an independent cohort of 8 breast cancer cell lines and LCLs derived from the same donor. Our data suggests that at least a portion of the individual sensitivity to capecitabine is shared between germline tissue and tumor tissue. It also supports the utility of patient-derived LCLs as a predictive model for capecitabine treatment efficacy in breast cancer patients.

Keywords: breast cancer; capecitabine; ex vivo model; lymphoblastoid cell lines; patient-derived model.

Figure 1. 5′-DFUR sensitivity obtained from patient-derived LCLs can be used to predict breast cancer patients' PFS

Kaplan-Meier curve represents PFS of stratified patients based on their LCL sensitivity to 5′-DFUR. 18 patients who have greater than mean ex vivo 5′-DFUR treatment AUC were compared to 17 patients who have lesser than mean ex vivo 5′-DFUR treatment AUC. Patients with lower AUC had a median 9 months PFS compared to those with higher AUC who only had a median of 6 months PFS (log rank p = 0.017).

Figure 2. Cellular sensitivity to 5′-DFUR assessed in LCLs and their matched breast cancer cell lines

(A) Decreased cellular viability was observed in both breast cancer (BC) cell lines and their matched LCLs when treated with increasing concentrations of 5′-DFUR for 72 hours. (B) Comparing cellular sensitivity to 5′-DFUR in both the BC cell lines and their matched LCLs. Student's t-test p = 0.0004 shows a significant difference in cellular response between BC cell lines and their matched LCLs in Area under the % viability curve (AUC) was calculated using trapezoidal rules. (C) AUC correlation between BC cell lines and their matched LCLs. Pearson correlation: r = 0.857 and p = 0.0067.

Figure 3. Effects of other anti-tumor drugs on 2 pairs of matching BC cell lines and LCLs

HCC1954, HCC1937 and their matched LCLs were treated with (A) lapatinib (B) daunorubicin and (C) paclitaxel at their pharmacological concentrations. Percent cell viability was analyzed after 72 hours treatment with respective drugs. *p < 0.05.