Dysregulation of the Rb pathway in recurrent pleomorphic adenoma of the salivary glands

Increased MIB-1 expression in salivary gland pleomorphic adenoma that recurs and undergoes malignant transformation

The objective of this retrospective study was to explore possible changes in histopathological features and expression of cyclin D1 and MIB-1 in salivary gland pleomorphic adenomas (PAs) that recur or undergo malignant transformation. Knowledge of these characteristics might help to guide the management of these rare tumors. The histopathology and immunohistochemical staining characteristics of such tumors were analyzed in a cohort of 65 patients constituting three different groups of tumors: PA, recurrent pleomorphic adenoma (RPA) and carcinoma ex PA (CxPA). The RPAs were divided into two subgroups: primary PA that were known to recur later (PA-prim) and recurrent tumors appearing after a primary tumor (PA-rec). RPAs and CxPAs were compared with PAs without recurrence, which served as a control group. In our study, CxPA and PA-rec, but not PA-prim, showed increased MIB-1 expression compared with the control group. Neither cyclin D1 expression nor any histopathological features showed any association in statistical analyses. CxPA showed increased mitotic activity, squamous metaplasia, and nuclear atypia. Tumor multifocality was more frequent in PA-rec and CxPA. The different MIB-1 expression in CxPA and PA-rec in comparison to PA-prim suggests that the changes in expression could develop after the primary tumor.

Knockdown of lncRNA ENST00000603829 Inhibits the Proliferation and Invasion of Salivary Gland Pleomorphic Adenoma through Regulating Cyclin D1

Objective

Salivary gland pleomorphic adenoma (SPA) is a benign neoplasm that can still recur even after radical surgery. To investigate its underlying pathogenesis, here, we examined the significance of lncRNA ENST00000603829 in the proliferation and invasion of SPA.

Methods

SPA tissues (n = 30) and adjacent normal tissues (NC; n = 30) were collected from SPA patients treated at our hospital from June 2017 to December 2019. The human normal salivary gland epithelial cell line (HSG) and SPA cells (PA30, PA37, and PA116) were cultured. qRT-PCR was used for detecting the expression of cyclin D1 and lncRNA ENST00000603829 in tissues and cells. lncRNA ENST00000603829/cyclin D1 was knocked down or overexpressed in PA116 cells. The expression of cyclin D1 and lncRNA ENST00000603829 in different cell lines was examined using qRT-PCR. Transwell assays and cell counting kit-8 (CCK-8) were used to assess cellular invasion and proliferation. The testing result regarding the apoptosis rate and cell cycle was obtained via flow cytometry. Western blot provided the measurement of cyclin D1 expression in cells.

Results

We observed an upregulation of lncRNA ENST00000603829 and cyclin D1 expression in SPA tissues and cells. Knockdown of lncRNA ENST00000603829 inhibited cell invasion and proliferation, promoting apoptosis and retaining the cells during the G0/G1 phase. However, such effects of lncRNA ENST00000603829 knockdown were inhibited when cyclin D1 was overexpressed.

Conclusion

lncRNA ENST00000603829 can promote the occurrence and development of SPA through increasing cyclin D1 expression.

Increase in Chymase-Positive Mast Cells in Recurrent Pleomorphic Adenoma and Carcinoma Ex Pleomorphic Adenoma of the Parotid Gland

Incomplete excision of pleomorphic adenoma (PA) may result in recurrent pleomorphic adenoma (RPA). Furthermore, long-term neglected PA may become carcinoma ex pleomorphic adenoma (CXPA). In the present study, the relationships between mast cell-derived chymase and these tumors were examined. The tumor tissues of PA consisted of either or both glandular and fibrotic structures. Histological features of RPA were almost similar to those of PA, except that they showed multinodular structures. CXPA is composed of a mixture of PA and carcinoma. The main stromal cells in PA were myofibroblasts, whereas fibroblasts constituted the main cellular portion in the stromal tissue of RPA. Cancer-associated fibroblasts (CAFs) were present abundantly in CXPA. With increased VEGF expression, neovascularization tended to increase in RPA or CXPA. Compared with PA, chymase-positive mast cells, as well as chymase gene expression, were increased in the tumor tissues from patients with RPA or CXPA. SCF, TGFβ1, and PCNA-positive staining was widely observed in these tumor tissues. The above results suggest that mast cell-derived chymase through its direct or cooperative effects with other mediators may participate in the pathophysiology of RPA and CXPA.

Expression of p16Ink4a protein in pleomorphic adenoma and carcinoma ex pleomorphic adenoma proves diversity of tumour biology and predicts clinical course

Aims

The aim of the study is to correlate p16^Ink4a expression with the clinical courses of pleomorphic adenoma (PA), its malignant transformation (CaexPA) and treatment outcomes.

Methods

Retrospective analysis (1998–2019) of 47 CaexPA, 148 PA and 22 normal salivary gland samples was performed. PAs were divided into two subsets: clinically ‘slow’ tumours characterised by stable size or slow growth; and ‘fast’ tumours with rapid growth rate.

Results

Positive p16^Ink4a expression was found in 68 PA and 23 CaexPA, and borderline expression in 80 and 20, respectively. All 22 (100%) normal salivary gland samples presented with no p16^Ink4a expression. Significant difference in p16^Ink4a expression was observed between normal tissue, PA and CaexPA (χ² (4)=172,19; p=0.0001). The PA clinical subgroups were also evaluated separately, revealing additional statistical relations: ‘fast’ PA and CaexPA differed significantly in p16Ink4a expression (χ² (2)=8.06; p=0.01781) while ‘slow’ PA and CaexPA did not (χ² (2)=3.09; p=0.2129). 3-year, 5-year and 10-year survival among p16^Ink4a positive CaexPA patients was 100%, 90.56% and 60.37%, respectively, and in CaexPA patients with borderline p16^Ink4a expression was 90.0%, 73.64% and 22.20%, respectively. Statistically significant difference between expression pattern and survival rate was observed (F Cox test – F (16, 24)=2.31; p=0.03075).

Conclusions

Our study confirms no p16^Ink4a expression in normal tissue, but reveals differences in expression between ‘fast’ and ‘slow’ PA. We suggest that p16^Ink4a overexpression is connected to PA proliferation and subsequent malignant transformation to CaexPA. Borderline p16^Ink4a staining correlates with worse prognosis of CaexPA.

Salivary Gland Pleomorphic Adenomas Presenting With Extremely Varied Clinical Courses. A Single Institution Case-Control Study

Objective

Pleomorphic adenomas (PAs) with divergent clinical behavior, differing from the vast majority of PAs, were distinguished. “Fast” PAs are characterized by an unexpectedly short medical history and relatively rapid growth. The reference group consisted of “slow” PAs with very stable biology and long-term progression. We divide the PA group as a whole into three subsets: “fast,” “normal,” and “slow” tumors. Our goal is a multifactorial analysis of the “fast” and “slow” PA subgroups.

Methods

Consecutive surgeries in a tertiary referral center, the Department of Otolaryngology and Laryngological Surgery, Poznan University of Medical Sciences, Poland, were carried out between 2002 and 2011. Out of 1,154 parotid tumors, 636 (55.1%) were PAs. The data were collected prospectively in collaboration with the Polish National Registry of Benign Salivary Gland Tumors. The main outcome measure was the recurrence rate in “fast” and “slow” PA subgroups. All surgical qualifications and surgeries were performed by two experienced surgeons.

Results

Slow PAs, compared to fast PAs, presented in older patients (53.25 ± 15.29 versus 47.92 ± 13.44 years). Multifactor logistic regression analysis with recurrence (yes/no) as the outcome variable, fast/slow as the predictor variable and age, gender, margin, FN status as covariates showed that fast PAs were significantly predicting recurrence vs. slow PAs (p = 0.035). Fast PAs were increasing the risk of PAs 10-fold vs. slow PAs, exp β = 10.20, CI₉₅ [1.66; 197.87]. The variables impacting relapse were recent accelerated growth of the tumor OR = 3.35 (SE = 0.56), p = 0.030, positive margins OR = 7.18 (SE = 0.57), p < 0.001, incomplete or bare capsule OR = 9.91 (SE = 0.53), p = 0.001 and location III OR = 3.12 (SE = 0.53), p = 0.033. In the multivariate model only positive margin was selected as the best predictor of relapse, OR = 5.01 (SE = 0.60), p = 0.007.

Conclusions

The simple clinical aspect of slow or fast PA progression is of great practical importance and can constitute a surrogate of the final histopathological information that is derived from the surgical specimen. The slow or fast nature of the PA to some extent indicates prognostic features such as recurrence risk. This finding requires correlation with histological and molecular features in further stages of research.

Somatic copy number alterations in pleomorphic adenoma and recurrent pleomorphic adenoma

OBJECTIVE

As the genetic changes in recurrent pleomorphic adenoma (RPA) have not yet been investigated, the aim of this study was to assess the genomic profile of somatic copy number alteration in RPA and pleomorphic adenoma (PA) by using array comparative genomic hybridization (aCGH).

STUDY DESIGN

Four cases of RPA and 13 cases of PA were evaluated by using aCGH, using a 180 K platform. Data were analyzed by using Nexus Copy Number Discovery.

RESULTS

The RPA group rarely showed any copy number alteration, except for 1 case that exhibited losses in 5 p15.33 p15.1, 5 q13.1 q35.3 and 12 q12 q13.11. The PA group also showed few copy number alterations, and the most frequent findings involved chromosomes 8: 8p21.3-p12 (gain), 8q12.1 (loss), 8p23.3-q24.3 (gain), and 8q12.1-q21.11 (gain). Genomic amplifications were revealed in the PA group, and the relevant affected genes were MAML2 and LIFR.

CONCLUSIONS

PA and RPA exhibit few somatic copy number alterations and show a similar genomic profile on aCGH.

Estrogen Receptor, Progesterone Receptor, and HER-2 Expression in Recurrent Pleomorphic Adenoma

Pleomorphic adenoma (PA) is the most common salivary gland neoplasm and, although mostly benign, recurrences, being called recurrent pleomorphic adenoma (RPA) and malignant transformation to carcinoma ex pleomorphic adenoma (CXPA), do occur. Recently, attention has been focused on molecular targeted cancer therapy in various tumors, including salivary gland tumors. The aim of this study was to investigate the role of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER-2) in PA, RPA, and CXPA. In total, 20 cases of PA, 18 of RPA, and 7 cases of CXPA were immunohistochemically studied for ER, PR, and HER-2. For evaluation of ER and PR, only nuclear expression and greater than 10% positive cells were regarded as cutoff criteria. HER-2 was evaluated semiquantitatively and graded from 0 to 3+. HER-2 amplification was assessed by chromogenic in situ hybridization (CISH). Tumors were negative for ER, PR, and HER-2 in all cases of PA and RPA. A case of CXPA showed moderate and complete membranous staining, and 6 cases were negative. HER-2 amplification was not observed in any case. In conclusion, the lack of ER, PR, and HER-2 expression in PA, RPA, and CXPA suggests that these proteins are not involved in progression, recurrence, or malignant transformation of PA.

Immunohistochemical expression of mammaglobin in salivary duct carcinomas de novo and salivary duct carcinoma ex pleomorphic adenoma

Mammaglobin is expressed in breast and salivary gland secretory carcinomas; however, its expression in salivary duct carcinomas (SDCs) still not well established. Therefore, the aim of this study was to investigate the presence and distribution of mammaglobin immunoexpression in SDC ex-PA in different phases of the adenoma to carcinoma sequence evaluating its possible involvement in carcinogenesis and tumor progression, as well as to determine its expression in SDC de novo. Mammaglobin immunohistochemistry was performed in 84 SG tumors, including 41 pleomorphic adenomas (PA) without malignant transformation, 13 intracapsular SDC ex-PA, 5 frankly invasive SDC ex-PA, 25 SDC de novo and 10 secretory carcinomas. The reactions were qualitatively analyzed and digitally scored. Positive immunostaining for mammaglobin was observed in 37 out of 84 SG tumors evaluated (44.1%), but strong staining was consistently seen only in secretory carcinomas, SDC de novo and frankly invasive SDC ex-PA, while it was weaker in intracapsular SDC ex-PA and PA. In PA, mammaglobin expression was significantly associated with recurrence. This study has confirmed that the mammaglobin is commonly expressed in SDC de novo and secretory carcinomas. Its expression was higher in SDC ex-PA than in PA, suggesting that mammaglobin may play a role in its malignant transformation.

The relationship between proteoglycan inhibition via xylosyltransferase II silencing and the implantation of salivary pleomorphic adenoma

OBJECTIVE

To study the relationship between proteoglycan inhibition and the implantation of salivary pleomorphic adenoma (SPA).

METHODS

SPA fresh tissue was primitively cultured and identified. The Ad-shRNA-XT-II adenovirus vector was constructed and transfected into SPA cells to silence the XT-II gene. The expression of the XT-II gene and protein was detected using real-time PCR and Western blotting, respectively. The proteoglycan content of the cells was determined 48 h after transfection. The invasion and migration of SPA cells were observed using Matrigel invasion and wound-healing assays. Fibroblasts from the tumour capsule of the same patient were obtained, cultured and seeded onto an acellular dermal matrix (ADM) scaffold. Tumour cells were seeded onto the scaffold with the fibroblasts and then transferred to BALB/C-nu nude mice and allowed to grow in vivo for 3 months.

RESULTS

The SPA cells cultures were positive for human calponin, S-100 protein, α-SMA and CK. XT-II gene and protein expression was decreased by 42.72% and 34%, respectively. The proteoglycan content was downregulated by 41.15%. XT-II gene silencing decreased the invasion and migration abilities of SPA cells. The assessment of SPA growth in nude mice indicated an absence of tumour growth in the SPA-XT-II group (in which the XT-II gene was silenced), whereas SPA growth was observed in the other two groups (in which the XT-II gene was not silenced), and the tumour tissue was positive for the human S-100 protein, α-SMA and CK8&18.

CONCLUSION

Proteoglycan inhibition induced via XT-II gene silencing inhibited the implantation of SPA.

PLAG1 expression is maintained in recurrent pleomorphic adenoma

The proto-oncogene (pleomorphic adenoma gene 1 (PLAG1)) is immunohistochemically overexpressed in pleomorphic adenoma (PA). Its expression in recurrent pleomorphic adenoma (RPA), however, has not been investigated. Since complex mechanisms are involved in tumor recurrence, the aim of this study was to investigate whether PLAG1 overexpression occurs in RPA. We studied PLAG1 protein expression in 40 PAs and 36 RPAs by immunohistochemistry. Cases with immunopositive cells were classified into two categories, between 10 and 50 % and >50 %. In both groups, PLAG1 expression was observed in both epithelial and myoepithelial cells. Of PAs, 37 cases (93 %) were positive, while this was the case in 34 RPA cases (94 %). Our findings suggest that in addition to morphological similarity, PA and RPA express PLAG1, which might play a role in tumor recurrence. Furthermore, as for PA, expression of PLAG1 can be considered a valuable diagnostic marker for RPA.