Detection of HER2 amplification in formalin-fixed paraffin-embedded breast carcinoma tissue with digital PCR using two TFF3 sequences as internal reference

Digital PCR quantification of ultrahigh ERBB2 copy number identifies poor breast cancer survival after trastuzumab

HER2/ERBB2 evaluation is necessary for treatment decision-making in breast cancer (BC), however current methods have limitations and considerable variability exists. DNA copy number (CN) evaluation by droplet digital PCR (ddPCR) has complementary advantages for HER2/ERBB2 diagnostics. In this study, we developed a single-reaction multiplex ddPCR assay for determination of ERBB2 CN in reference to two control regions, CEP17 and a copy-number-stable region of chr. 2p13.1, validated CN estimations to clinical in situ hybridization (ISH) HER2 status, and investigated the association of ERBB2 CN with clinical outcomes. 909 primary BC tissues were evaluated and the area under the curve for concordance to HER2 status was 0.93 and 0.96 for ERBB2 CN using either CEP17 or 2p13.1 as reference, respectively. The accuracy of ddPCR ERBB2 CN was 93.7% and 94.1% in the training and validation groups, respectively. Positive and negative predictive value for the classic HER2 amplification and non-amplification groups was 97.2% and 94.8%, respectively. An identified biological "ultrahigh" ERBB2 ddPCR CN group had significantly worse survival within patients treated with adjuvant trastuzumab for both recurrence-free survival (hazard ratio, HR: 3.3; 95% CI 1.1-9.6; p = 0.031, multivariable Cox regression) and overall survival (HR: 3.6; 95% CI 1.1-12.6; p = 0.041). For validation using RNA-seq data as a surrogate, in a population-based SCAN-B cohort (NCT02306096) of 682 consecutive patients receiving adjuvant trastuzumab, the ultrahigh-ERBB2 mRNA group had significantly worse survival. Multiplex ddPCR is useful for ERBB2 CN estimation and ultrahigh ERBB2 may be a predictive factor for decreased long-term survival after trastuzumab treatment.

Development and Evaluation of a Droplet Digital PCR Assay for 8p23 β-Defensin Cluster Copy Number Determination

Introduction

It has been proposed that the copy number (CN) variation (CNV) in β-defensin genes (DEFB) on human chromosome 8p23 determines phenotypic differences in inflammatory diseases. However, no method for accurate and easy DEFB CN quantification is yet available.

Objective

Droplet digital polymerase chain reaction (ddPCR) is a novel method for CNV quantification and has been used for genes such as CCL4L, CCL3L1, AMY1, and HER2. However, to date, no ddPCR assay has been available for DEFB CN determination. In the present study, we aimed to develop and evaluate such a ddPCR assay.

Methods

The assay was designed using DEFB4 and RPP30 as the target and the reference gene, respectively. To evaluate the assay, 283 DNA samples with known CNs previously determined using the multiple ligation-dependent probe amplification (MLPA) method, the current gold standard, were used as standards. To discover the optimal DNA template amount, we tested 80 to 2.5 ng DNA by a serial of one to two dilutions of eight samples. To evaluate the reproducibility of the assay, 31 samples were repeated to calculate the intra- and inter-assay variations. To further validate the reliability of the assay, the CNs of all 283 samples were determined using ddPCR. To compare results with those using quantitative PCR (qPCR), DEFB CNs for 48 samples were determined using qPCR with the same primers and probes.

Results

In a one-dimensional plot, the positive and negative droplets were clearly separated in both DEFB4 and RPP30 detection channels. In a two-dimensional plot, four populations of droplets were observed. The 20 ng template DNA proved optimal, with either high (80 ng) or low (10, 5, 2.5 ng) template input leading to ambiguous or inaccurate results. For the 31 standard samples, DEFB CNs were accurately determined with small intra- and inter-assay variations (coefficient of variation < 0.04 for both). In the validation cohort, ddPCR provided the correct CN for all 283 samples with high confidence. qPCR measurements for the 48 samples produced noisy data with high uncertainty and low accuracy.

Conclusions

ddPCR is an accurate, reproducible, easy-to-use, cheap, high-throughput method for DEFB CN determination. ddPCR could be applied to DEFB CN quantification in large-scale case–control studies.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40291-021-00546-2.

Detection of human papillomavirus infection in laryngeal and hypopharyngeal carcinoma using droplet digital PCR and its correlation with prognosis

OBJECTIVE

To use droplet digital polymerase chain reaction (ddPCR) to detect human papillomavirus (HPV) infection in squamous cell carcinoma of the larynx and hypopharynx (SCCLHP) and to analyze its association with the prognosis of patients with HPV.

METHODS

We used ddPCR for HPV detection in 114 patients with SCCLHP; clinical data were collected, and the patients were followed-up for prognosis analysis. Univariate and multivariate Cox regression analyses were used to complete the analysis of risk factors. This clinical study was registered (clinical trial registration no. ChiCTR2000033032).

RESULT

Of the total cases, 15.79% (18/114) were HPV-positive and 8 (8/18, 44.4%) patients had tumors with HPV-16. There was a significant correlation between HPV-16 and the T classification and Tumor-Node-Metastasis (TNM) (P = 0.025 and 0.036, respectively). The 3-year overall survival rates in the HPV-positive and HPV-negative patients were 39.8% and 48.6% (P = 0.776), respectively. In the univariate analysis, HPV infection was not associated with the relative risk of progression (hazard ratio [HR] = 1.109, P = 0.778). Patients with laryngeal carcinoma (HR = 1.805, P = 0.037), no alcohol consumption (HR = 0.430, P = 0.009), well-differentiated tumors (HR = 2.570, p = 0.006), TNM I-II (HR = 2.482, P = 0.003), and no lymph node metastasis (HR = 2.615, P = 0.001) had better prognoses. In the multivariate analysis, tumor location (HR = 3.044, P = 0.001), alcohol consumption (HR = 0.474, P = 0.022), tumor differentiation (HR = 2.131, P = 0.030), and lymph node metastasis (HR = 4.179, P < 0.001) were independent predictors of better overall survival in SCCLHP.

CONCLUSION

ddPCR is an advanced technology that can accurately diagnose HPV infection with high specificity and sensitivity. The HPV infection rate in SCCLHP was low, and there was no significant difference in the prognosis of SCCLHP.