INTRODUCTION
NUT carcinoma (midline testicular carcinoma nuclear protein) is a relatively new entity
that, because of its poor recognition, becomes underdiagnosed. The aggressive nature
is marked, with presence of lymph node involvement and / or metastatic invasion. The
preferred metastatic NUT carcinoma sites are distal lymph nodes, bone marrow and pleura[1]
[2]. Expression of the NUT protein is usually exclusive to the testes and its expression
outside the testis is diagnostic of NMC (NUT midline carcinoma)[3]
[4].
It has been postulated that these tumors arise from remnants of epithelial progenitor
cells that are observed early in life in the first two to three decades. This hypothesis
was further supported by the frequent immunoexpression of CD34, a marker of the stem
cell phenotype in cells of this tumor. The incidence of NMC remains unknown due to
its rarity, lack of pathognomonic morphological features and the need for molecular
diagnostic methods, such as fluorescence in situ hybridization (FISH) or reverse transcriptase
(PCR), which unfortunately are not available in most laboratories in the world. The
recent development of an immunohistochemical staining for NUT, which proved to be
sensitive and specific for the diagnosis of CMN, led to an increase in the number
of diagnosed cases and in patients of any age presenting “undifferentiated carcinoma”,
antibody immunostaining NUT must be extensivelyperformed to allow definitive diagnosis
in histology and immunohistochemistry, which can then be characterized by FISH or
RT-PCR[1].
Although their sites of involvement are generally defined as in medial structures
of the head and neck and in the mediastinum, other sites may be affected, such as
the larynx, and even in socalled common structures, the clinical course may impress.
Data on mediastinal NUT midline carcinoma with extensive cardiac invasion have been
reported in two cases and in one case it was possible to demonstrate extensive coronary
involvement that causes a fatal myocardial infarction[5]. Another study reports the second case that appears in the lacrimal fossa[6].
Because it is one of the most common sites of involvement, it is reported here the
clinic that can be found in head and neck NUT tumors: proptosis, decreased vision,
nasal obstruction and epistaxis. However, a brief clinical history with rapidly progressive
tumor mass is present in all cases.
Because incidence rates and published data are lacking, there is no standardized treatment
for NUT midline carcinoma.
The objective of this systematic review was therefore to describe the pathophysiological
characteristics of NUT carcinoma and, mainly, to analyze the types of treatments used
and their efficacy, in order to improve the knowledge about the subject, to decrease
the rate of underdiagnosis and to guide the possible treatments, in view of experiences
held by other professionals and demonstrated in other articles.
METHODS
The systematic review of the literature is a form of synthesis of the information
available at any given time on a specific topic. It is a scientific investigation
that brings together relevant studies on a formulated question, using the database
of the literature that deals with a question as a source and methods of identification,
selection and systematic analysis, with the purpose of performing a critical and comprehensive
review of the literature. Therefore, the systematic review seeks to overcome possible
bias in all stages, following a rigorous method of searching and selecting the research.
In this context, this work began with the elaboration of the clinical question, that
is, the main objective, and of a revision project. Next, a careful analysis was carried
out in the literature with the objective of identifying the largest possible number
of studies related to the subject.
Once selected, criteria for methodological quality evaluation were applied according
to the design of the original study, with emphasis on the academic relevance of the
selected material.
Thus, an electronic literature search was performed in the Medline database, using
the keyword “NUT carcinoma”, which contained articles from 01/01/2001 to 12/31/2018.
We identified 755 articles and submitted to the inclusion criteria: articles published
in the period; Languages English, Portuguese and Spanish; case report or case series,
cohort, control case, literature review, double-blind randomized controlled trials
and meta-analyzes. From this, 70 valid articles for the proposal were selected and
submitted to the exclusion criteria: article with duplicate databases or incomplete
access, inadequate methodologies to the proposed objective, non-corresponding or tangential
abstract to the central theme of the research and article not reviewed by expert.
At the end, there were 15 articles relevant to the theme, which were read in full,
so that each contributed to the construction of the present study.
RESULTS AND DISCUSSION
NUT midline carcinoma is a relatively recent entity, recognized and considered one
of the most aggressive solid human malignancies. It is a genetically defined neoplasm[6]
[7]. Tumors tend to distribute along the midline axis with a predilection for head and
neck, mediastinum, and lung. In addition, there are rare reports of involvement of
the primary bladder, breast, endometrium, kidney and orbit[8]. There is a propensity for early metastases in the lymph nodes and lungs, and the
tumors are almost inevitably fatal. Based on the frequent expression of keratin, it
has been concluded that the NUT midline carcinoma represents a carcinoma. The presence
of squamous keratinization led to the classification of the midline NUT carcinoma
as a subtype of squamous cell carcinoma.
The incidence of NUT-associated tumors is unknown and occurs mainly in adolescents
and young adults, and is most commonly found in the second and third decades of life[8], and it is assumed that cases in soft tissues and viscera have not been recognized
until now[9]. More than 80% of patients die in the first year of diagnosis of NUT carcinoma;
locoregional and distant metastases are common and, in addition to complete surgical
resection, there is currently limited therapeutic benefit of chemoradiotherapy. The
prognosis remains extremely poor, with a median survival of 6.7 months and an overall
survival of 19% in the first two years after diagnosis[9].
Pathophysiology involves a rearrangement of the NUT gene on chromosome 15q14 with
members of the BRD gene family (BRD4 and BRD3) resulting in a BRD- NUT fusion product,
which decreases histone acetylation and therefore suppresses squamous cell differentiation.
Pathological examination may reveal positivity for cytokeratins (CKs) and p63, a squamous
basal cell marker, leading to an incorrect diagnosis of squamous cell carcinoma[9].
The recent availability of a commercially available NUT antibody for immunohistochemistry
facilitated the diagnosis of NMC, providing an economical and robust method to distinguish
it from other low differentiated carcinomas[6]. Positive immunoreactivity for anti-CK antibodies AE1 / AE3, as well as EMA (a marker
for the epithelial nature of neoplastic cells), p63 and p40 (basal cell carcinoma
markers) are the usual immunohistochemical findings and should raise suspected carcinoma
NUT in young individuals with a tumor in the midline[9].
Nuclear positivity of more than 50% for the antiNUT antibody with fluorescence in
situ hybridization (FISH) analysis allows the diagnosis of NUT carcinoma with 100%
specificity. The characterization of both BRD4-NUT and BRD3-NUT fusion genes, and
more rarely NSD3-NUT, is not mandatory for diagnosis but is recommended for itspossible
association with unique prognostic features. NUT carcinomas without the BRD4 fusion
gene rearrangements are more differentiated and therefore possibly less aggressive[9].
It was predicted that a set of 18, 33 and 34 miRNAs (micro RNAs) targeted the transcript
of the BRD4NUT fusion gene, BRD4 mRNA and NUT, respectively. The comparative analysis
of these miRNAs and functional enrichment of the pathway revealed that a set of 48
miRNA can be deregulated to target critical genes other than parental genes (BRD4
and NUT), causing cancer. The amplification at the level of expression of these miRNAs
can be used for the diagnosis and prognosis of CMN[1].
Currently, there is no consensus on the optimal treatment strategy. In the absence
of optimal treatment, platinum-based regimens and lymphoma types were used[10]. In addition to its rarity, the NUT midline carcinoma may initially and transiently
respond to several cytotoxic agents used to treat undifferentiated carcinomas, making
it less likely to give rise to the correct diagnostic suspicion. Regardless of the
treatment chosen, the activity was at most transient and short duration[2].
Initial non-surgical treatment is employed in most patients, and the majority of patients
undergoing definitive radiation were head and neck. Chemotherapy was also used as
part of the treatment[11]. However, the low chemoSensitivity of NUT carcinoma is proven, with a very transient
response rate to chemotherapy of approximately 36%, rapidly followed by tumor progression,
independently of the pharmacological schemes used[12].
Other combinations of second or subsequent conventional chemotherapy were not effective.
Responses to chemotherapy with anthracyclines and alkylating agents (ifosfamide) have
also been reported in the literature, but with limited efficacy. In a review of the
literature based on 31 cases of NUT intrathoracic carcinoma in adults, it was concluded
that the best treatment option was a combination of cisplatin, gemcitabine and docetaxel.
However, only transient responses were obtained[12].
As the currently available chemotherapy regimens are ineffective, new therapies have
been developed for this cancer, supported by preclinical studies reporting a positive
response to HDAC14 inhibitors (histone deacetylase inhibitors), such as vorinostat,
and BRD inhibitors (inhibitors of bromodomain), which induce the squamous differentiation
of NUT carcinoma cells and block their growth, however, the use of the NUT has been
limited due to serious side effects[12].
Several phase I / II clinical trials have been completed or are underway using BRD
inhibitors (TEN010 protein inhibitors [NCT01987362], GSK525762 [NCT01587703], MK-8628
[NCT02698176], INCB057643 [NCT02711137], BAY1238097 [NCT02369029] ) CUDC907 [NCT02307240])
which could effectively have a place in the treatment of this disease, possibly as
firstline treatment alone or in combination with other therapeutic agents, in view
of the poor prognosis of this tumor. Therefore, NUT carcinoma is essential to propose
the inclusion of these patients in targeted therapeutic studies as soon as possible[12].
In terms of local treatment, patients undergoing complete surgery and / or initial
radiotherapy had significantly higher disease-free survival and progression-free survival.
Local treatments appear to be potentially useful for controlling disease, especially
when localized[13].
In the literature, a patient with NUT carcinoma has been reported to be cured and
with long-term follow-up: a 10-year-old male, treated in 1991, with a 10-cm tumor
involving iliac bone with soft tissue extension. Cytogenetic analysis revealed a translocation
(15; 19) (q13; p13) and FISH reported a specific translocation of BRD4- NUT. This
patient was treated with conventional chemotherapy with alternating cycles of vincristine
/ doxorubicin / ifosfamide and cisplatin / doxorubicin / ifosfamide combined with
focal radiotherapy according to the Scandinavian protocol of inoperable Ewing's sarcoma.
The patient remained in complete remission 13 years after treatment[13].
In one study, two cases, the first of a nine-year-old boy with enlarged cervical lymph
nodes, and a sublingual gland identified as the site of the primary tumor, and the
second of a nine-year-old boy with swelling of the left cheek and magnetic resonance
imaging revealing a 1.3 × 3 cm mass gently rising over the masseter muscle, contiguous
with the parotid gland, entered complete remission after initiation of treatment using
chemotherapy according to the protocol of the Scandinavian Sarcoma Group (SSG) IX
for inoperable Ewing's Sarcoma. This protocol provides for 4 cycles of chemotherapy,
each including two courses of VAI (vincristine, adriamycin and ifosfamide) alternating
with a course of PAI (cisplatin, adriamycin and ifosfamide). To avoid late toxicity
of cumulative high doses of drugs, 3 cycles were given. Radiotherapy was applied to
all involved regions simultaneously[13].
Another study provides a framework for deconvolution and prediction of genotype-chemootype
relationships in a large-scale kinase inhibitor screen and identifies CDK9 as a drugable
target in NMC. One of the most notable specific vulnerabilities of genotypes on our
screen was the excellent activity of LDC67, a known inhibitor of CDK9 in NMC cells.
The chemical genomics approach revealed a role for CDK9 as a non-oncogenic factor
for tumorigenesis in BRD4-NUT-dependent cells mediated by transcriptional regulation
and Myc protein levels in NMC. It is indicated that the inhibition of BRD4 leads to
the dissolution of hyperacetylated nuclear foci, release of p53 with induction of
p21, cell cycle arrest and differentiation. CDK9 may be an attractive drug target
in NMC patients.
Inhibition of CDK9 specifically modulates transcriptional elongation and effectively
impairs viability by inducing apoptosis and DNA damage response of NUT midline carcinoma
cells[14]. In the past, clinical studies investigating spectrum CDK inhibitors such as dinaciclib
or flavopiridol have reported high rates of dose-limiting side effects and toxicities,
but more selective compounds such as ribocyclib (CDK4 and CDK6) have demonstrated
the feasibility of inhibiting CDK even as treatment of first line cancer. For this
reason, several CDK9 inhibitors with better selectivity profiles have been developed
and promising for future development in clinical applications. Such findings may therefore
be relevant to the future development of these drugs and to the stratification of
patients receiving these types of selective CDK9 inhibitors[14].
Another point is the observed elevation of alpha-fetoprotein in NUT medial carcinoma,
which may be related to the suggested hypothesis that these cells arise from cells
derived from the primitive neural crest. In fact, both the gene expression profile
similar to the adult ciliary ganglion and the absence of the in-situ component are
consistent with that cell of origin. Alpha-fetoprotein levels during treatment were
not reported in the majority of available cases. Considering these findings, it is
suggested not to exclude and, instead, to take into account the diagnosis of NUT medial
carcinoma when facing a patient with a rapidly growing nodule in the midline structures
and elevation of alpha-fetoprotein. Of course, assessment of alpha- fetoprotein levels
in other cases of medullary NUT carcinoma may help to better define the role of this
serum marker in this challenging disease. It is suggested to measure alpha-fetoprotein
levels during tumor treatment to monitor the course of the disease[2].
Several publications advocate a multimodal strategy that adapts to the aggressive
behavior of NUT carcinoma. In line with this, an aggressive combined approach with
radiotherapy and surgery, whenever possible, as part of the initial multimodal treatment
should be used[15].
Due to the rarity, the data that are available are limited, especially in relation
to the care standards and prognostic factors of that tumor, that is uniformly weak.
Cases report metastasis via the hematogenic route, in addition to almost all patients
succumbing to the disease, despite aggressive management strategies, thus emphasizing
the lethal behavior of this neoplasm.
