Trophoblast Cell Surface Antigen 2 (Trop-2) Protein is Highly Expressed in Salivary Gland Carcinomas and Represents a Potential Therapeutic Target

Adenoid Cystic carcinoma of minor salivary glands (AdCCmSG): a multidisciplinary update

INTRODUCTION

Adenoid cystic carcinoma of minor salivary glands (AdCCmSG) represents a 'rarity in the rarity,' posing a clinical challenge in lack of standardized, evidence-based recommendations. At present, AdCCmSG management is mostly translated from major salivary gland cancers (MSGCs). Ideally, AdCCmSG diagnostic-therapeutic workup should be discussed and carried out within a multidisciplinary, high-expertise setting, including pathologists, surgeons, radiation oncologists and medical oncologists.

AREAS COVERED

The present review provides an overview of epidemiology and pathologic classification. Moreover, the most recent, clinically relevant updates in the treatment of AdCCmSG (Pubmed searches, specific guidelines) are critically discussed, aiming to a better understanding of this rare pathologic entity, potentially optimizing the care process, and offering a starting point for reflection on future therapeutic developments.

EXPERT OPINION

The management of rare cancers is often hindered by limited data and clinical trials, lack of evidence-based guidelines, and hardly represented disease heterogeneity, which cannot be successfully tackled with a 'one-size-fits-all' approach. Our goal is to address these potential pitfalls, providing an easy-to-use, updated, multidisciplinary collection of expert opinions concerning AdCCmSG management as of today's clinical practice. We will also cover the most promising future perspectives, based on the potential therapeutic targets highlighted within AdCCmSG's molecular background.

Current diagnosis and treatment of salivary gland-type tumors of the lung

Salivary gland-type tumors of the lung are thought to originate from the submucosal exocrine glands of the large airways. Due to their rare occurrence, reports of their study are limited to small-scale or case reports. Therefore, daily clinical practices often require a search for previous reports. In the last 20 years, several genetic rearrangements have been identified, such as MYB::NF1B rearrangements in adenoid cystic carcinoma, CRTC1::MAML2 rearrangements in mucoepidermoid carcinoma, EWSR1::ATF1 rearrangements in hyalinizing clear cell carcinoma and rearrangements of the EWSR1 locus or FUS (TLS) locus in myoepithelioma and myoepithelial carcinoma. These molecular alterations have been useful in diagnosing these tumors, although they have not yet been linked to molecularly targeted therapies. The morphologic, immunophenotypic, and molecular characteristics of these tumors are similar to those of their counterparts of extrapulmonary origin, so clinical and radiologic differential diagnosis is required to distinguish between primary and metastatic disease of other primary sites. However, these molecular alterations can be useful in differentiating them from other primary lung cancer histologic types. The management of these tumors requires broad knowledge of the latest diagnostics, surgery, radiotherapy, bronchoscopic interventions, chemotherapy, immunotherapy as well as therapeutic agents in development, including molecularly targeted agents. This review provides a comprehensive overview of the current diagnosis and treatment of pulmonary salivary gland tumors, with a focus on adenoid cystic carcinoma and mucoepidermoid carcinoma, which are the two most common subtypes.

The Relationship between Trop-2, Chemotherapeutic Drugs, and Chemoresistance

Trop-2 is a highly conserved one-pass transmembrane mammalian glycoprotein that is normally expressed in tissues such as the lung, intestines, and kidney during embryonic development. It is overexpressed in many epithelial cancers but is absent in non-epithelial tumors. Trop-2 is an intracellular calcium signal transducer that participates in the promotion of cell proliferation, migration, invasion, metastasis, and probably stemness. It also has some tumor suppressor effects. The pro-tumoral actions have been thoroughly investigated and reported. However, Trop-2's activity in chemoresistance is less well known. We review a possible relationship between Trop-2, chemotherapy, and chemoresistance. We conclude that there is a clear role for Trop-2 in some specific chemoresistance events. On the other hand, there is no clear evidence for its participation in multidrug resistance through direct drug transport. The development of antibody conjugate drugs (ACD) centered on anti-Trop-2 monoclonal antibodies opened the gates for the treatment of some tumors resistant to classic chemotherapies. Advanced urothelial tumors and breast cancer were among the first malignancies for which these ACDs have been employed. However, there is a wide group of other tumors that may benefit from anti-Trop-2 therapy as soon as clinical trials are completed.

Locally Advanced Adenoid Cystic Carcinoma of the Breast-A Case Report with a Review of the Literature

Breast cancer (BC) is a heterogeneous disease distinguished by four main subtypes based on the expression of estrogen, progesterone receptors, and human epidermal growth factor-2 on the cancer cells. Triple-negative breast cancer (TNBC) consists of approximately 10-20% of all BCs and is characterized by a poor prognosis. Adenoid cystic carcinoma (ACC) of the breast is a rare, special type of TNBC with low metastatic potential and usually favorable prognosis. There are no established recommendations concerning systemic therapy in advanced ACC. We present a case of a 70-year-old woman with locally advanced ACC with progression after radical mastectomy, and review the literature concerning the treatment of metastatic disease focused on systemic therapy.

Nectin-4 is frequently expressed in primary salivary gland cancer and corresponding lymph node metastases and represents an important treatment-related biomarker

Many locally advanced and metastatic salivary gland carcinomas (SGC) lack therapeutic targets. Enfortumab vedotin, an antibody-drug conjugate binding to Nectin-4, recently gained FDA approval for third-line urothelial carcinoma. Therefore, the aim of this study was to assess the expression of Nectin-4 in primary SGC and corresponding lymph node metastases and to correlate it with clinicopathological data. Immunohistochemical staining for Nectin-4 was performed for patients who had undergone surgery with curative intent for primary SGC of the parotid or submandibular gland in a tertiary referral center between 1990 and 2019. One hundred twenty-two primary SGC and twenty corresponding lymph node metastases were included. Nectin-4 was expressed in 80.3% of primary SGC with a mean Histo(H-)score of 61.2 and in 90.0% of lymph node metastases with a mean H-score of 75.6. A moderate or high Nectin-4 expression was found in 25.9% of salivary duct carcinomas (SaDu) and in 30.7% of adenoid cystic carcinomas (ACC). SaDu patients with a lower T-stage (p = 0.04), no loco-regional lymph node metastases (p = 0.049), no vascular invasion (p = 0.04), and no perineural spread (p = 0.03) showed a significantly higher mean Nectin-4 H-score. There was a statistical tendency towards a more favorable disease-free survival among SaDu patients with a higher Nectin-4 expression (p = 0.09). Nectin-4 is expressed in SGC and therefore represents a potential therapeutic target, especially in entities with a high rate of local recurrence and metastatic spread such as SaDu and ACC.

Current management and future challenges in salivary glands cancer

Salivary gland cancers (SGCs) are rare, accounting for less than 5% of all malignancies of the head and neck region, and are morphologically heterogeneous. The diagnosis is mainly based on histology, with the complementary aid of molecular profiling, which is helpful in recognizing some poorly differentiated, borderline, or atypical lesions. Instrumental imaging defines the diagnosis, representing a remarkable tool in the treatment plan. Ultrasound and magnetic resonance are the most common procedures used to describe the primary tumour. The treatment of SGCs is multimodal and consists of surgery, radiotherapy, and systemic therapy; each treatment plan is, however, featured on the patient and disease's characteristics. On 24 June 2022, in the meeting "Current management and future challenges in salivary gland cancers" many experts in this field discussed the state of the art of SGCs research, the future challenges and developments. After the meeting, the same pool of experts maintained close contact to keep these data further updated in the conference proceedings presented here. This review collects the insights and suggestions that emerged from the discussion during and after the meeting per se.

Targeting Trop-2 in cancer: Recent research progress and clinical application

The development of new antitumor drugs depends mainly upon targeting tumor cells precisely. Trophoblast surface antigen 2 (Trop-2) is a type I transmembrane glycoprotein involved in Ca2+ signaling in tumor cells. It is highly expressed in various tumor tissues than in normal tissues and represents a novel and promising molecular target for caner targeted therapy. Up to now, the mechanisms and functions associated with Trop-2 have been extensively studied in a variety of solid tumors. According to these findings, Trop-2 plays an important role in cell proliferation, apoptosis, cell adhesion, epithelial-mesenchymal transition, as well as tumorigenesis and tumor progression. In addition, Trop-2 related drugs are also being developed widely. There are a number of Trop-2 related ADC drugs that have demonstrated potent antitumor activity and are currently been studied, such as Sacituzumab Govitecan (SG) and Datopotamab Deruxtecan (Dato-Dxd). In this study, we reviewed the progress of Trop-2 research in solid tumors. We also sorted out the composition and rationale of Trop-2 related drugs and summarized the related clinical trials. Finally, we discussed the current status of Trop-2 research and expanded our perspectives on its future research directions. Importantly, we found that Trop-2 targeted ADCs have great potential for combination with other antitumor therapies. Trop-2 targeted ADCs can reprogramme tumor microenvironment through multiple signaling pathways, ultimately activating antitumor immunity.

Advances in Trop2-targeted therapy: Novel agents and opportunities beyond breast cancer

Trop2 is a transmembrane glycoprotein and calcium signal transducer with limited expression in normal human tissues. It is consistently overexpressed in a variety of malignant tumors and participates in several oncogenic signaling pathways that lead to tumor development, invasion, and metastasis. As a result, Trop2 has become an attractive therapeutic target in cancer treatment. The anti-Trop2 antibody-drug conjugate (Trodelvy™, sacituzumab govitecan) has been approved to treat metastatic triple-negative breast cancer. However, it is still unclear whether the success observed in Trop2-positive breast cancer could be replicated in other tumor types, owing to the differences in the expression levels and functions of Trop2 across cancer types. In this review, we summarize the recent progress on the structures and functions of Trop2 and highlight the potential diagnostic and therapeutic value of Trop2 beyond breast cancer. In addition, the promising novel Trop2-targeted agents in the clinic were discussed, which will likely alter the therapeutic landscape of Trop2-positive tumors in the future.

Multi-Class Cancer Subtyping in Salivary Gland Carcinomas with MALDI Imaging and Deep Learning

Salivary gland carcinomas (SGC) are a heterogeneous group of tumors. The prognosis varies strongly according to its type, and even the distinction between benign and malign tumor is challenging. Adenoid cystic carcinoma (AdCy) is one subgroup of SGCs that is prone to late metastasis. This makes accurate tumor subtyping an important task. Matrix-assisted laser desorption/ionization (MALDI) imaging is a label-free technique capable of providing spatially resolved information about the abundance of biomolecules according to their mass-to-charge ratio. We analyzed tissue micro arrays (TMAs) of 25 patients (including six different SGC subtypes and a healthy control group of six patients) with high mass resolution MALDI imaging using a 12-Tesla magnetic resonance mass spectrometer. The high mass resolution allowed us to accurately detect single masses, with strong contributions to each class prediction. To address the added complexity created by the high mass resolution and multiple classes, we propose a deep-learning model. We showed that our deep-learning model provides a per-class classification accuracy of greater than 80% with little preprocessing. Based on this classification, we employed methods of explainable artificial intelligence (AI) to gain further insights into the spectrometric features of AdCys.

CD138 Is Expressed in Different Entities of Salivary Gland Cancer and Their Lymph Node Metastases and Therefore Represents a Potential Therapeutic Target

Advanced salivary gland carcinomas (SGC) often lack therapeutic options. Agents targeting CD138 have recently shown promising results in clinical trials for multiple myeloma and a preclinical trial for triple-negative breast cancer. Immunohistochemistry for CD138 was performed for all patients who had undergone primary surgery for SGC with curative intent. Findings were validated using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) imaging. Overall, 111 primary SGC and 13 lymph node metastases from salivary duct carcinomas (SaDu) were evaluated. CD138 expression was found in 60% of all SGC with differing expression across entities (p < 0.01). A mean of 25.2% of the tumor cells in mucoepidermoid carcinoma (MuEp) were positive, followed by epithelial-myoepithelial carcinoma (20.9%), acinic cell carcinoma (16.0%), and SaDu (15.2%). High-/intermediate-grade MuEp showed CD138 expression in a mean of 34.8% of tumor cells. For SaDu, lymph node metastases showed CD138 expression in a mean of 31.2% of tumor cells which correlated with CD138 expression in their primaries (p = 0.01; Spearman’s ρ = 0.71). MALDI-MS imaging confirmed the presence of the CD138 protein in SGC. No significant association was found between clinicopathological data, including progression-free survival (p = 0.50) and CD138 expression. CD138 is expressed in the cell membrane of different entities of SGC and SaDu lymph node metastases and therefore represents a potential target for CD138 targeting drugs.

Metastatic Adenoid Cystic Carcinoma: Genomic Landscape and Emerging Treatments

OPINION STATEMENT

Adenoid cystic carcinoma (ACC) is a heterogeneous cancer that commonly develops in the salivary glands. Approximately 40 to 50% of patients with ACC develop recurrence and/or metastasis. Although most patients with ACC have slow-growing disease, a subset experiences aggressive disease with early visceral and/or bone metastasis. Thus far, there is no consensus on the best time to start palliative treatment in patients with indolent disease. The only systemic therapies available for recurrent or metastatic ACC are cytotoxic agents and multikinase inhibitors targeting vascular endothelial growth factor receptor, and both types of therapy have modest activity. Studies integrating proteomics, genomics, and clinical data have revealed distinct molecular ACC subtypes, ACC-I and ACC-II, with ACC-I generally associated with more aggressive disease biology. ACC-I tumors were enriched for NOTCH1-activating mutation and upregulation of MYC and MYC targets, while ACC-II tumors exhibited upregulation of TP63 and receptor tyrosine kinases. These findings highlight the importance of patient selection for surveillance and targeted therapy development in ACC. In recent clinical trials of targeted therapy in ACC, patients are being selected according to tumor molecular profile (e.g., presence of NOTCH-activating mutations), which represents a major advance in the field. Ongoing collaborative research focusing on the development of novel therapeutic strategies for ACC patients based on disease biology will increase the drug armamentarium and improve survival outcomes for these patients in dire need.

TROP2 Expression in Sebaceous and Sweat Gland Carcinoma

Sebaceous carcinoma and sweat gland carcinoma (malignant tumors with apocrine and eccrine differentiation) are rare malignant skin adnexal tumors that differentiate toward sebaceous gland and eccrine and apocrine glands, respectively. Owing to the rarity of these carcinomas, standard treatments for advanced disease have not been established. Because the prognosis of patients with systemic metastasis is poor, a new treatment for these diseases is eagerly desired. Trophoblast cell surface antigen 2 (TROP2) and sacituzumab govitecan, an antibody–drug conjugate of TROP2, have attracted attention in the treatment of various solid tumors. In the current study, we immunohistochemically investigated TROP2 expression in 14 sebaceous carcinoma and 18 sweat gland carcinoma samples and found strong and relatively homogeneous TROP2 staining in both cancer types. The mean Histoscore, a semi-quantitative scoring ranging from 0 (negative) to 300, was 265.5 in sebaceous carcinoma and 260.0 in sweat gland carcinoma. These observations directly suggest that both sebaceous carcinoma and sweat gland carcinoma could be potentially treated with TROP2-targeted antibody–drug conjugates such as sacituzumab govitecan.

Proteomics in support of immunotherapy: contribution to model-based precision medicine

INTRODUCTION

Proteomics encompasses a wide and expanding range of methods to identify, characterize, and quantify thousands of proteins from a variety of biological samples, including blood samples, tumors, and tissues. Such methods are supportive of various forms of immunotherapy applied to chronic conditions such as allergies, autoimmune diseases, cancers, and infectious diseases.

AREAS COVERED

In support of immunotherapy, proteomics based on mass spectrometry has multiple specific applications related to (i) disease modeling and patient stratification, (ii) antigen/ autoantigen/neoantigen/ allergen identification, (iii) characterization of proteins and monoclonal antibodies used for immunotherapeutic or diagnostic purposes, (iv) identification of biomarkers and companion diagnostics and (v) monitoring by immunoproteomics of immune responses elicited in the course of the disease or following immunotherapy.

EXPERT OPINION

Proteomics contributes as an enabling technology to an evolution of immunotherapy toward a precision medicine approach aiming to better tailor treatments to patients' specificities in multiple disease areas. This trend is favored by a better understanding through multi-omics profiling of both the patient's characteristics, his/her immune status as well as of the features of the immunotherapeutic drug.

A New Kid on the Block: Sacituzumab Govitecan for the Treatment of Breast Cancer and Other Solid Tumors

Human trophoblast cell-surface antigen-2 (Trop-2) is a membrane glycoprotein involved in cell proliferation and motility, frequently overexpressed in epithelial tumors. Thus, it represents an attractive target for anticancer therapies. Sacituzumab govitecan (SG) is a third-generation antibody-drug conjugate, consisting of an anti-Trop-2 monoclonal antibody (hRS7), a hydrolyzable linker, and a cytotoxin (SN38), which inhibits topoisomerase 1. Specific pharmacological features, such as the high antibody to payload ratio, the ultra-toxic nature of SN38, and the capacity to kill surrounding tumor cells (the bystander effect), make SG a very promising drug for cancer treatment. Indeed, unprecedented results have been observed with SG in patients with heavily pretreated advanced triple-negative breast cancer and urothelial carcinomas, and the drug has already received approval for these indications. These results are coupled with a manageable toxicity profile, with neutropenia and diarrhea as the most frequent adverse events, mainly of grades 1-2. While several trials are exploring SG activity in different tumor types and settings, potential biomarkers of response are under investigation. Among these, Trop-2 overexpression and the presence of BRCA1/2 mutations seem to be the most promising. We review the available literature concerning SG, with a focus on its toxicity spectrum and possible biomarkers of its response.

Trop-2 Therapy in Metastatic Triple-Negative Breast Cancer in Italy: Clinical Opportunity and Regulatory Pitfalls

Trop-2 is an ideal candidate for targeted therapeutics because it is a transmembrane protein with an extracellular domain overexpressed in a wide variety of tumors, and is upregulated in normal cells. Consequently, several Trop-2-targeted drugs have recently been developed for clinical use, such as anti-Trop-2 antibodies. Sacituzumab govitecan, a Trop-2-directed antibody and topoisomerase inhibitor drug conjugate, was recently approved by the Food and Drug Administration (FDA) and European Medicines Agency (EMA) for the treatment of metastatic triple-negative breast cancer and metastatic urothelial cancer. In Italy, this treatment cannot be used in clinical practice because it has not yet been approved by the Agenzia Italiana del Farmaco (AIFA, Rome, Italy). In Italy, this is not a new problem, in fact, when a new compound is approved by the U.S. and Europe, there is often a delay in its approval for use. The adoption of universal guidelines and the standardization of Trop-2 evaluation is urgently needed.

Antibody-Antineoplastic Conjugates in Gynecological Malignancies: Current Status and Future Perspectives

In the last decade, antibody-drug conjugates (ADCs), normally formed by a humanized antibody and a small drug via a chemical cleavable or non-cleavable linker, have emerged as a potential treatment strategy in cancer disease. They allow to get a selective delivery of the chemotherapeutic agents at the tumor level, and, consequently, to improve the antitumor efficacy and, especially to decrease chemotherapy-related toxicity. Currently, nine antibody-drug conjugate-based formulations have been already approved and more than 80 are under clinical trials for the treatment of several tumors, especially breast cancer, lymphomas, and multiple myeloma. To date, no ADCs have been approved for the treatment of gynecological formulations, but many formulations have been developed and have reached the clinical stage, especially for the treatment of ovarian cancer, an aggressive disease with a low five-year survival rate. This manuscript analyzes the ADCs formulations that are under clinical research in the treatment of gynecological carcinomas, specifically ovarian, endometrial, and cervical tumors.

Trop2 Expression in Extramammary Paget's Disease and Normal Skin

Extramammary Paget's disease (EMPD) is a rare skin cancer arising in the apocrine gland-rich areas. Most EMPD tumors are dormant, but metastatic lesions are associated with poor outcomes owing to the lack of effective systemic therapies. Trophoblast cell surface antigen 2 (Trop2), a surface glycoprotein, has drawn attention as a potential therapeutic target for solid tumors. Sacituzumab govitecan, an antibody-drug conjugate of Trop2, has recently entered clinical use for the treatment of various solid cancers. However, little is known about the role of Trop2 in EMPD. In this study, we immunohistochemically examined Trop2 expression in 116 EMPD tissue samples and 10 normal skin tissues. In normal skin, Trop2 was expressed in the epidermal keratinocytes, inner root sheaths, and infundibulum/isthmus epithelium of hair follicles, eccrine/apocrine glands, and sebaceous glands. Most EMPD tissues exhibited homogeneous and strong Trop2 expression, and high Trop2 expression was significantly associated with worse disease-free survival (p = 0.0343). These results suggest the potential use of Trop2-targeted therapy for EMPD and improve our understanding of the skin-related adverse effects of current Trop2-targeted therapies such as sacituzumab govitecan.