Transcriptomic profiling of a late recurrent nuclear protein in testis carcinoma of the lung 14 years after the initial operation: a case report
Case Report

Transcriptomic profiling of a late recurrent nuclear protein in testis carcinoma of the lung 14 years after the initial operation: a case report

Taketo Kato1 ORCID logo, Hironori Oyamatsu2, Yuki Hanamatsu3, Heng Huang1, Shoji Okado1, Yoshito Imamura1, Yuji Nomata1, Hiroki Watanabe1, Yuka Kadomatsu1, Harushi Ueno1, Shota Nakamura1, Tetsuya Mizuno1, Tetsunari Hase4, Tamotsu Takeuchi3, Toyofumi Fengshi Chen-Yoshikawa1

1Department of Thoracic Surgery, Nagoya University Graduate School of Medicine, Nagoya, Japan; 2Department of Thoracic Surgery, Okazaki City Hospital, Aichi, Japan; 3Department of Pathology and Translational Research, Gifu University Graduate School of Medicine, Gifu, Japan; 4Department of Respiratory Medicine, Nagoya University Graduate School of Medicine, Nagoya, Japan

Contributions: (I) Conception and design: T Kato, H Oyamatsu; (II) Administrative support: TF Chen-Yoshikawa; (III) Provision of study materials or patients: Y Kadomatsu, H Ueno, S Nakamura, T Mizuno, T Hase; (IV) Collection and assembly of data: H Huang, S Okado, Y Imamura, Y Nomata, H Watanabe; (V) Data analysis and interpretation: Y Hanamatsu, T Takeuchi; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors.

Correspondence to: Toyofumi Fengshi Chen-Yoshikawa, MD, PhD. Department of Thoracic Surgery, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466-8550, Japan. Email: tyoshikawa@med.nagoya-u.ac.jp.

Background: Nuclear protein in testis (NUT) carcinoma (NC) of the lung is a rare cancer that occurs mainly in young adolescents and adults. NC is genetically characterized by NUTM1 rearrangements, which usually take the form of BRD4-NUT fusions. The prognosis for NC is dismal, and treatment with conventional chemotherapeutic regimens is ineffective.

Case Description: We herein describe the case of a 53-year-old woman with recurrent NC of the lung 14 years after surgery for nasal cavity cancer. Chest computed tomography revealed a 5.5-cm tumor in the lower lobe of the left lung. We completely resected the recurrent lung NC via thoracotomy. Immunohistochemistry (IHC) of the lung and nasal cavity cancers showed diffuse strong expression of NUT. RNA-seq of the lung NC revealed NUTM1 rearrangement, with a fusion of BRD4 exon 10 to NUTM1 exon 4. This breakpoint has never been reported before. In addition, IHC revealed elevated expression of parathyroid hormone-like hormone in the lung NC but not in the nasal cavity NC, indicating that the lung and nasal cavity NCs were metachronous multiple primary cancers.

Conclusions: We experienced a rare recurrence of lung NC 14 years after the initial surgery. The BRD4-NUT fusion consisted of a new breakpoint. Furthermore, the expression pattern of parathyroid hormone-like hormone (PTHLH) suggested that the NCs in the nasal cavity and lung may be metachronous multiple lung cancers. This extremely rare case highlighted the possibility of identifying less malignant NCs in patients with poorly differentiated tumors via fusion gene analysis and the need to develop more effective treatment strategies for this malignancy.

Keywords: BRD4-NUT; parathyroid hormone-like hormone (PTHLH); late recurrence; extraterminal domain; case report

Submitted Mar 22, 2024. Accepted for publication Jun 24, 2024. Published online Jul 11, 2024.

doi: 10.21037/tlcr-24-259

Highlight box

Key findings

• Transcriptome profiling of a resected case of late recurrent nuclear protein in testis (NUT) carcinoma (NC) of the lung demonstrated a BRD4-NUT fusion, which may have influenced the favorable prognosis of this patient.

What is known and what is new?

• NC of the lung is a rare cancer and the prognosis is dismal. This disease is genetically characterized by NUTM1 rearrangements, which usually take the form of BRD4-NUT fusions.

• RNA-seq of the recurrent lung NC revealed NUTM1 rearrangement, with fusion of BRD4 exon 10 to NUTM1 exon 4. This breakpoint has never been reported before. In addition, immunohistochemistry revealed elevated parathyroid hormone-like hormone in the recurrent lung NC but not in the nasal cavity NC, indicating that the lung and nasal cavity NCs were metachronous multiple primary cancers.

What is the implication, and what should change now?

• This rare case provides evidence for NC with a favorable prognosis and supports the utility of fusion gene analysis to predict prognosis.

Introduction

Nuclear protein in testis (NUT) carcinoma (NC) of the lung is a rare malignancy that predominantly affects adolescents and young adults. NC occurs in the upper aerodigestive tract, particularly the sinonasal area. NC cases of the lung or mediastinum are extremely rare; only few cases have been reported to date (1). NC is characterized by the rearrangement of NUT. The NUT rearrangements usually form BRD4-NUT fusions, but BRD3-NUT or NUT-variant fusions are formed in a minority of cases (2,3). Treatment of NC with conventional chemotherapeutic regimens is ineffective, and the prognosis of patients with NC remains poor. Herein, we describe the case of a woman with recurrent NC of the lung 14 years after the removal of NC from the nasal cavity. The pathology of this rare disease and the relationship between the primary and recurrent tumors were investigated through RNA-seq and immunohistochemical analysis of the tumor tissue. We present this article in accordance with the CARE reporting checklist (available at https://tlcr.amegroups.com/article/view/10.21037/tlcr-24-259/rc).

Case presentation

A 53-year-old woman was referred to Nagoya University Hospital for examination of a tumor in the left lung after its detection via computed tomography (CT) (Figure 1). The patient was generally in good condition and had a history of spinocerebellar degeneration and surgery for nasal cavity cancer 14 years ago, which existed on middle nasal meatus and was 3.2 cm in size. Chest CT revealed a 5.5-cm tumor in the lower lobe of the left lung. The left inferior pulmonary vein (PV) was obstructed by the tumor, but no intrapericardial invasion was detected (Figure 1). Fluorodeoxyglucose (FDG) positron emission tomography revealed high accumulation of FDG in the tumor (maximum standard uptake was 7.25) but no accumulation in the hilar and mediastinal lymph nodes or distant metastases. After bronchoscopy, the tumor was diagnosed as squamous cell carcinoma and left lower lobectomy was planned.

Figure 1 Preoperative chest computed tomography scan showing a 5.5-cm tumor in the left lower lobe (yellow arrow).

Surgery was performed via thoracotomy, with the patient under general anesthesia. The tumor was located in the left lower lobe and extended into the extrapericardial PV. The pulmonary ligament was cut and PV was secured and resected within the pericardial sac. The lower lobe pulmonary artery was dissected and cut with a surgical stapler. After dissection of the subcarinal lymph nodes, the lower lobe bronchus was divided with a stapler. The upper mediastinal lymph nodes were also dissected. The postoperative course was uneventful. The chest tube was removed on postoperative day 2, and the patient was discharged without complications on postoperative day 6. Postoperative systemic therapy was not administered because the lung cancer was completely resected and no metastasis was detected on pathological diagnosis. Two years after surgery, the patient developed putaminal hemorrhage, and CT revealed metastasis of NC to the chest wall. The patient died by suicide in the same year.

Histopathological examination revealed that the nasal cavity cancer diagnosed 14 years ago also formed solid alveoli of poorly differentiated cells (Figure 2A). In the lung tumor, poorly differentiated proliferative cells with heteromorphic nuclei infiltrated and formed large and small solid alveoli with keratinization (Figure 2B). No pericardial involvement or lymph node metastases were observed. Immunohistochemical analysis revealed tumor cells in both the nasal cavity and lung with diffuse strong NUT expression (Figure 2C,2D). Although the nasal cavity cancer may have metastasized to the lung, the nasal cavity cancer was histologically more malignant in comparison with the lung cancer.

Figure 2 Histopathologic characteristics of the initial and recurrent tumors. Hematoxylin and eosin staining of the NUT carcinoma in the nasal cavity (A, ×40) and the lung (B, ×40). Both cancers formed solid alveoli of poorly differentiated cells. Immunohistochemistry for NUT in the nasal cavity (C, ×40 and ×400) and lung (D, ×40 and ×400) cancers demonstrated diffuse nuclear staining. NUT, nuclear protein in testis.

RNA-seq (Macrogen, Seoul Korea) of the lung cancer tissue was performed, and Arriba analysis of whole transcriptomic sequence data showed the fusion of BRD4 exon 10 to NUTM1 exon 4 (Figure 3). Breakpoints are usually located at exon 11 or 15 in BRD4 and exon 1b or 2 in NUTM1 (4). Differential gene expression analysis comparing RNA-seq data from this case and the GTEx (https://www.gtexportal.org/) normal lung dataset (Table 1) identified SOX2 and TP63, which were previously reported as NC-related genes (5). Immunohistochemical analysis of parathyroid hormone-like hormone (PTHLH), which was highly expressed in lung NC (Table 1), revealed negative staining in the previous nasal cavity cancer (Figure 4A) but positive in the lung cancer (Figure 4B). This finding suggests that the lung and nasal cavity NCs were metachronous multiple primary cancers. All procedures performed in this study were in accordance with the ethical standards of the institutional research committee and with the Declaration of Helsinki (as revised in 2013). This study was approved by the Ethics Committee for Human Research of the Faculty of Medicine of Nagoya University (#2017-0034). Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Figure 3 Genomic structure of BRD4-NUT translocation in this case.

Table 1

Top 30 genes specifically expressed in NUT carcinoma compared to normal lung tissue

Gene symbol NUT tissue (TPM) Normal lung (TPM) Fold change
PTHLH 1,598.0 0.6 1,000.5
SOX2 1,594.0 0.6 974.8
XIST 466.9 0.1 428.8
MIF 1,669.8 3.2 399.1
IGF2 3,969.3 9.2 389.1
TFAP2B 319.4 0.0 316.1
KRT5 1,389.7 3.6 303.9
CXCL11 547.3 1.5 219.0
LGALS7B 351.2 0.7 211.5
SOX2-OT 206.0 0.1 196.3
CA9 243.6 0.3 192.5
MYB 476.2 1.8 169.8
TP63 272.2 0.6 169.6
IRX4 158.4 0.0 156.4
SYT8 1,165.3 7.3 139.7
TFAP2A 171.2 0.2 138.3
ART3 161.8 0.3 128.1
RPL41P1 196.0 0.6 126.9
CALB1 114.1 0.1 100.6
GPR87 111.6 0.1 99.1
RN7SL4P 123.7 0.3 98.9
FOXD1 126.3 0.3 97.3
SNORA67 131.9 0.4 93.4
PNCK 129.2 0.4 93.0
PLEKHG4B 159.0 0.7 92.8
P2RY12 247.5 1.7 91.1
COL7A1 587.0 5.7 87.7
ZDHHC8P1 152.7 0.8 83.2
SERPINB5 92.8 0.1 82.8
TRIM74 124.7 0.5 82.1

NUT, nuclear protein in testis; TPM, transcripts per million.

Figure 4 Immunohistochemical staining for PTHLH was negative in the nasal cavity cancer (A, ×200) and positive in the lung cancer (B, ×100). PTHLH, parathyroid hormone-like hormone.

Discussion

NC is characterized by NUT rearrangements. The t(15:19) translocation, which brings NUT in frame with BRD4, is the most common rearrangement. BRD4 is a widely expressed transcriptional activator that promotes the expression of the BRD4-NUT fusion gene (6). Standard chemotherapeutic drugs and radiotherapy are ineffective in treating NC, and the prognosis and outcomes for patients with NC are unfavorable, with a median survival time of 6.5 months (7).

Currently, no standard treatment options are available for patients with NC. The only treatment for this case was surgery. However, new treatments that specifically address unique tumorigenic mechanisms are under investigation, including bromodomain and extraterminal (BET) inhibitors, histone deacetylase inhibitors (HDACi), and immunotherapies (8-10). BET inhibitors bind to the bromodomain and acetylated histones of BET proteins to reduce the expression of MYC, SOX2, and TP63. Unfortunately, the efficacy of BET inhibitors is limited, response rates are moderate, and response durations are only 2–3 months (11). Therefore, BET inhibitors are combined with other chemotherapies. HDACi reduce hyperacetylated chromatin in the BRD4 mega-domain and return cellular transcription to normal levels (12). To date, evidence supporting the efficacy of HDACi is lacking, and HDACi treatment cannot be recommended as a standard treatment for patients with NC.

In this case, we differentiated between metastatic and metachronous cancers. PTHLH was highly expressed in the lung cancer but not in the nasal cavity cancer. Although tumor heterogeneity and clonal evolution may influence the differences in protein expression between these two cancers (13), the higher pathological malignancy of the nasal cavity cancer and the long disease-free duration indicated that the cancers were metachronous primary cancers (14). Furthermore, PTHLH is a marker of poor prognosis. PTHLH stimulates in vitro cell proliferation in squamous cell carcinoma through the promotion of cell-cycle progression (15). Cyclin genes, including CCNA2, CCNE2, and CDC25A, are stimulated by PTHLH and contribute to cell-cycle checkpoint evasion and phase transition. Therefore, therapeutic agents that inhibit PTHLH expression, such as roxithromycin, may prevent the proliferation of NCs expressing PTHLH and complications associated with PTHLH-induced cancer (14).

Chau et al. (7) recently established a predictive risk model of survival outcomes based on the largest study cohort of patients with NC to date. Patients were classified into the following three risk groups based on anatomic site and NUTM1 fusion type: patients with nonthoracic primary NC and BRD3- or NSD3-NUTM1 fusion, patients with nonthoracic primary NC and BRD4-NUTM1 fusion, and patients with thoracic primary NC and any NUTM1 fusion type. Patients with nonthoracic BRD3- and NSD3-NUTM1 fusion tumors exhibited significantly longer overall survival rates than those with nonthoracic primary BRD4-NUTM1 fusion tumors. Patients with thoracic primary tumors exhibited worse outcomes than the other patient groups, regardless of the NUTM1 fusion type. In our case, the patient experienced no recurrence for 14 years after surgery for NC in the nasal cavity, but NC subsequently recurred in the left lung and metastasized to the chest wall 2 years after the second surgery. Although this case may be in line with previous reports, no metachronous NUT cancer cases separated by a long period have been reported due to the poor prognosis of NC.

Recurrence-free survival after surgery for thoracic NC was 2 years in this case. This prognosis was relatively favorable compared with that in previous reports (1,16). However, some thoracic NC cases with better prognoses have been reported. The cases with better outcomes were NUT variants involving BRD3 or other uncharacterized partner genes (17). Based on RNA-seq results, the NC was characterized as a BRD4-NUT fusion tumor in our case. Although this is a typical fusion gene for NC, the breakpoint was BRD4 exon 10 and NUTM1 exon 4, which are not typical breakpoints (4). The most common oncogenic variation in NC is an in-frame fusion of BRD4 exon 11 with the start of NUTM1 exon 2 (18,19). In the case reported here, the predicted protein domain structure of BRD4-NUT fusion consisted of two NUT protein families and three well-characterized BRD4 domains, including two bromodomains and the extraterminal (ET) domain (Figure 5) (20,21). The breakpoint of this case was in the ET domain of BRD4. Therefore, the ET domain of the fusion gene was incomplete. The ET domain regulates transcription factors (22,23). Thus, the low-grade malignancy and better prognosis of the NC may have been due to this new variant. Although complete resection of lung cancer improves survival and this is the only case with a breakpoint at BRD4 exon 10 and NUTM1 exon 4, this new variant may result in a favorable prognosis of NC.

Figure 5 Predicted protein domain structure of BRD4-NUT fusion in this case. BRD, bromodomain; ETD, extraterminal domain; NUTP, NUT protein; NUT, nuclear protein in testis.

Conclusions

We experienced a rare recurrence of lung NC 14 years after the initial surgery. The BRD4-NUT fusion consisted of a new breakpoint. Furthermore, the expression pattern of PTHLH suggested that the NCs in the nasal cavity and lung were metachronous multiple lung cancers. Although the prognosis of NC is usually very poor, this case highlights the possible identification of a more favorable prognosis of pulmonary NCs via gene fusion analysis. However, more effective treatment strategies for this malignancy are needed.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://tlcr.amegroups.com/article/view/10.21037/tlcr-24-259/rc

Peer Review File: Available at https://tlcr.amegroups.com/article/view/10.21037/tlcr-24-259/prf

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tlcr.amegroups.com/article/view/10.21037/tlcr-24-259/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional research committee and with the Declaration of Helsinki (as revised in 2013). This study was approved by the Ethics Committee for Human Research of the Faculty of Medicine of Nagoya University (#2017-0034). Written informed consent was obtained from the patient for publication of this case report and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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Cite this article as: Kato T, Oyamatsu H, Hanamatsu Y, Huang H, Okado S, Imamura Y, Nomata Y, Watanabe H, Kadomatsu Y, Ueno H, Nakamura S, Mizuno T, Hase T, Takeuchi T, Chen-Yoshikawa TF. Transcriptomic profiling of a late recurrent nuclear protein in testis carcinoma of the lung 14 years after the initial operation: a case report. Transl Lung Cancer Res 2024;13(7):1756-1762. doi: 10.21037/tlcr-24-259

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