Generation and evaluation of a monoclonal antibody, designated MAdL, as a new specific marker for adenocarcinomas of the lung

Abstract

Background: Different therapy regimens in non-small-cell lung cancer (NSCLC) are of rising clinical importance, and therefore a clear-cut subdifferentiation is mandatory. The common immunohistochemical markers available today are well applicable for subdifferentiation, but a fraction of indistinct cases still remains, demanding upgrades of the panel by new markers.

Methods: We report here the generation and evaluation of a new monoclonal antibody carrying the MAdL designation, which was raised against primary isolated human alveolar epithelial cells type 2.

Results: Upon screening, one clone (MAdL) was identified as a marker for alveolar epithelial cell type II, alveolar macrophages and adenocarcinomas of the lung. In a large-scale study, this antibody, with an optimised staining procedure for formalin-fixed tissues, was then evaluated together with the established markers thyroid transcription factor-1, surfactant protein-A, pro-surfactant protein-B and napsin A in a series of 362 lung cancer specimens. The MAdL displays a high specificity (>99%) for adenocarcinomas of the lung, together with a sensitivity of 76.5%, and is capable of delivering independent additional diagnostic information to the established markers.

Conclusion: We conclude that MAdL is a new specific marker for adenocarcinomas of the lung, which helps to clarify subdifferentiation in a considerable portion of NSCLCs.

Figure 1

Photomicrograph of IHC on FFPE tissues targeting MAdL, with red colour indicating positive signal. Immunoreactivity of MAdL in AECII (indicated with arrow) and intra-alveolar macrophages (indicated with star; A, × 1000, indicated with arrows), as well as a case of corresponding adenocarcinoma of the lung (B, × 400) is depicted in the upper part. Non-malignant tissues of proximal kidney tubules (C, × 200) as well as chromophile renal cell carcinoma (D, × 200) are shown in the centre lane. Lymph node (E, × 200) and spleen tissue (F, × 200) housing non-alveolar macrophages are all negative for MAdL.

Figure 2

Bar plot depicting general sensitivity (A) of applied IHC markers on 167 adenocarcinomas of the lung and sensitivity depending on grading (B) or specimen origin (C). Thyroid transcription factor-1 was expressed in 154 out of 167 (92.2%) cases of adenocarcinomas and MAdL in 124 out of 167 (74.2) cases. The surfactant proteins SP-A and SP-B were found to be expressed in 92 (55%) and 88 (52.6%) of 167 samples, respectively.

Figure 3

Observed expression patterns of applied IHC markers for 167 cases of adenocarcinomas of the lung. Within the observed patterns, 55 (32.7%) cases were positive for all the markers. Thyroid transcription factor-1 alone was observed in 21 cases (12.5%) and MAdL alone in 2 cases (1.1%). Thyroid transcription factor-1 and MAdL as the only expressed markers were observed in 25 cases (14.9%), whereas TTF-1/MAdL/SP-A or TTF-1/MAdL/SP-B stated for 21 (12.5%) or 16 (9.5%) cases, respectively. Expression of TTF-1 and SP-A or TTF-1 with both surfactant proteins counted for each seven (4.1%) cases. Less frequent combinations of markers included TTF-1/SP-B, MAdL/SP-A, MAdL/SP-B, MAdL/SP-A/SP-B and SP-A/SP-B and were grouped as ‘other’ with 4.7%. No expression of any marker was observed in six cases (3.5%). The possible diagnostic benefit of MAdL is displayed with ‘#’ and accounts for 27 cases (16%) within the investigated collective.

Figure 4

Photomicrograph of IHC on a case of pleura carcinosis from pulmonary adenocarcinoma origin. Hematoxylin–eosin-stained overview (A). No expression of either SP-A or SP-B was observed (data only shown for SP-A; B). Targeting TTF-1 resulted in strong nuclear (C) or cytoplasmic staining for MAdL (D). All images were at × 400 magnification.

Figure 5

Photomicrograph of IHC on a case of adenosquamous carcinoma of the lung. Squamous-differentiated tumour component revealed a strong CK5/6 positivity (A). Adenoid component of the tumour shows a distinct nuclear signal for TTF-1 (B) and a patchy staining for SP-B (C). Cytoplasmic signals for MAdL could be observed, in contrast to TTF-1, in the majority of glands (D).