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Year : 2016  |  Volume : 59  |  Issue : 3  |  Page : 301-304
The evaluation of the caveolin-1 and AT-rich interactive domain 1 alpha expressions in uterine smooth muscle tumors

1 Pathology Laboratory, Tepecik Training and Research Hospital, Izmir, Turkey
2 Gynecologic Oncology Clinics, Tepecik Training and Research Hospital, Izmir, Turkey

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Date of Web Publication10-Aug-2016


Objectives: This retrospective study was designed to evaluate the importance of tissue expressions of caveolin-1 (Cav-1) and AT-rich interactive domain 1 alpha (ARID-1A) which are known as signal regulator and tumor suppressor in differential diagnosis of uterine smooth muscle tumors (SMTs). Materials and Methods: Thirty patients recently diagnosed as uterine SMTs at the Tepecik Training and Research Hospital were identified using pathology databases. Immunohistochemical stains for Cav-1 and ARID-1A were performed. Results: In this series, there were 10 leiomyosarcomas (LMSs), 10 uterine smooth muscle tumors of uncertain malignant potentials (STUMPs), and 10 leiomyomas (LMs). Cav-1 expression located cytoplasmic or perivascular area. Cytoplasmic Cav-1 expression was determined in 5 LMSs and 2 STUMPs while perivascular Cav-1 expression was determined in 9 LMSs and 2 STUMPs. Statistically, it was determined that if the tumor becomes malignant and more invasive, it gains the perivascular Cav-1 expression (P = 0.029). On the other hand, the mean nuclear staining rate for ARID-1A in LMSs (63 ± 23.4%) was higher than both STUMPs (60 ± 18.5%) and LMs (34.5 ± 16.5%). Statistically, it was determined that the expression of ARID-1A was significantly downregulated in LMs when compared with STUMPs and LMSs (P = 0.004). Conclusions: Our findings were demonstrated that perivascular Cav-1 expression was seen to be a marker for malignancy of uterine SMTs. Similarly, we found to link of ARID-1A expression and the aggressiveness of SMTs. Therefore, it may be suggested that Cav-1 and ARID-1A may act as predictive biomarkers in uterine SMTs.

Keywords: AT-rich interactive domain 1 alpha, caveolin-1, smooth muscle tumor, uterus

How to cite this article:
Ayaz D, Diniz G, Kahraman DS, Sayhan S, Uncel M, Karadeniz T, Sanci M. The evaluation of the caveolin-1 and AT-rich interactive domain 1 alpha expressions in uterine smooth muscle tumors. Indian J Pathol Microbiol 2016;59:301-4

How to cite this URL:
Ayaz D, Diniz G, Kahraman DS, Sayhan S, Uncel M, Karadeniz T, Sanci M. The evaluation of the caveolin-1 and AT-rich interactive domain 1 alpha expressions in uterine smooth muscle tumors. Indian J Pathol Microbiol [serial online] 2016 [cited 2022 Sep 26];59:301-4. Available from:

   Introduction Top

Smooth muscle tumors (SMTs) are the most frequent mesenchymal tumors of the uterus. The majority of the uterine SMTs are readily classifiable as leiomyoma (LM) or leiomyosarcoma (LMS) based on its gross and microscopic appearances.[1] Uterine SMTs which cannot be histologically diagnosed as unequivocally benign or malignant currently termed “smooth muscle tumor of uncertain malignant potential” (STUMP). STUMPs represent a heterogeneous group of rare tumors that have been the subject of only a few published studies, some of which lack detailed clinicopathologic details and/or follow-up data.[1],[2] More recently, it has been suggested that immunohistochemical staining for Ki-67 proliferation index and mitotic count may be helpful in the differential diagnosis of uterine SMTs.[1],[2],[3]

Caveolae, specialized plasmalemmal organelles, are flask-shaped invaginations of the plasma membrane and have three different coat proteins, named as caveolin (Cav). The Cav proteins (Cav-1, -2, and -3) serve as the structural components of caveolae while also functioning as scaffolding proteins, capable of recruiting numerous signaling molecules to caveolae, as well as regulating their activity.[4],[5] Cav-1 is widely coexpressed in fully differentiated mesenchymal and endothelial normal tissues as well as in many solid tumors.[5],[6] Recently, it was suspected that numerous disease processes may be affected by ablation or mutation of CAVs which regulate many signaling molecules and signaling cascades.[4] Previous studies revealed that levels of Cav-1 in epithelial cells of some carcinomas increase during tumor progression. Conversely, Cav-1 expression in the peritumoral stromal cells can decline in advanced and metastatic cancer.[6],[7] Similar results also were determined in sarcomas.[8] Although Cav-1 has been shown to act as either a tumor suppressor or tumor promoter in different tumors, there were only a few studies about the Cav-1 function in SMTs.[9],[10]

AT-rich interactive domain 1 alpha (ARID-1A) is a tumor suppressor gene located in 1p36.11 region which is frequently deleted in human cancers. It encodes the ARID-1A protein (BAF250a or p270) which is a subunit of the SWI/SNF chromatin remodeling complex.[11] In addition, ARID-1A mutation frequently coexists with activating mutations of PIK3CA and/or loss of PTEN expression, which both lead to a downstream activation of the PI3K/AKT pathway.[12] Recent studies have shown the loss of ARID-1A expression in various, predominantly gynecological cancers. However, the functional and prognostic significance of ARID-1A was not fully understood in most tumors.[11],[12],[13]

The aim of the present study was to investigate the both Cav-1 and ARID-1A immunohistochemical expressions in SMTs of the uterus and evaluate the relationship with these expressions and many other prognostic findings such as age, tumor size, Ki-67 proliferation index, and mitosis.

   Materials and Methods Top

The myomectomy or hysterectomy specimens of 30 cases diagnosed and treated in Izmir Tepecik Education and Research Hospital between 2009 and 2013 were included in this study. The study was approved by the Local Ethics Committee.

For immunohistochemistry (IHC) studies, hematoxylin and eosin staining was used to select appropriate paraffin blocks and identify the viable tumor areas. IHC was performed by the streptavidin-biotin peroxidase method (Invitrogen, Camarillo, 85-9043). Serial 5 μm sections were obtained and these slides were baked overnight at 60°C, dewaxed in xylene, and hydrated with distilled water through decreasing concentrations of alcohol. All slides were treated with heat-induced epitope retrieval in the microwave (in 10 mM/L citrate buffer, pH 6.0, for 20 min, followed by cooling at room temperature for 20 min) and blocked for endogenous peroxidase and biotin. The purified monoclonal mouse antibodies against Cav-1 (Novus Biologicals, Littleton, NB100-615) and ARID-1A (Sigma, St. Louis, HPA005456) are used at a dilution of 1: 200. The evaluation was blinded to any of the clinical features. Staining patterns of Cav-1 were classified as cytoplasmic, cytoplasmic, and perivascular or only perivascular in tumors. ARID-1A expression presented as the strong nuclear staining, and we counted the rate of nuclear positivity. Spearman Correlation analysis, Mann–Whitney U-test, Chi-square test, and Kaplan–Meier survival analyses were performed for statistical analysis with IBM SPSS Statistics. P < 0.05 was considered to be statistically significant.

   Results Top

In this series, there were 10 LMSs, 10 uterine STUMPs, and 10 LMs. The mean age of patients was 48.1 ± 13.7 years (ranging from 23 to 77 years). The cases with LMSs (58.2 ± 10.06 years/44–77 years) were older than cases with both STUMPs (46.6 ± 12.5/23–72 years) and LMs (39.6 ± 12.2 years/23–59 years). The mean diameter of tumors was 8.03 ± 5.7 cm (ranging from 2 to 22 cm). Mean mitoses count was 2.9 ± 1.5 in STUMPs while mean mitoses count was 13.3 ± 3.3 in LMSs. Similarly, the mean percentile of Ki-67 expression was higher in LMSs than STUMPs [Table 1].
Table 1: Detailed histopathological findings of the uterine smooth muscle tumors

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Cytoplasmic Cav-1 expression was determined in 5 (50%) LMSs [Figure 1]a and 2 STUMPs (20%) while perivascular Cav-1 expression was determined in 9 LMSs (90%) and 2 (20%) STUMPs [Figure 1]b. Perivascular Cav-1 expressions were absent in all LMs and most STUMPs (n: 8/80%). Statistically, it was determined that if the tumor becomes malignant and more invasive, it gains the perivascular Cav-1 expression (P = 0.029). Furthermore, there were parallel changes between tumoral Cav-1 expressions and tumor types except the LMs (P = 0.005).
Figure 1: (a) Cytoplasmic staining patterns in leiomyosarcomas with anti-caveolin1 antibody and (b) perivascular staining patterns in smooth muscle tumors of uncertain malignant potential with anti-caveolin1 antibody at the right (DAB, ×100). I provided patches

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ARID-1A expressions were determined as strong nuclear staining pattern in all tumors [Figure 2]. The mean nuclear staining rate for ARID-1A in LMSs (63 ± 23.4%) was higher than both STUMPs (60 ± 18.5%) and LMs (34.5 ± 16.5%). Statistically, it was determined that the expression of ARID-1A was significantly downregulated in LMs when compared with STUMPs and LMSs (P = 0.004). Our findings were demonstrated to link of ARID-1A expression and the aggressiveness of SMTs. However, unlike previous studies, the ARID-1A expression was downregulated in benign tumors. In addition, we determined an association between the perivascular Cav-1 and ARID-1A expressions (P = 0.016). Mean nuclear ARID-1A rate was 47.17 ± 22.19.5 in tumors with perivascular Cav-1 expressions while it was 70 ± 17.3 in others.
Figure 2: (a) Strong nuclear staining patterns in smooth muscle tumors of uncertain malignant potential with anti-AT-rich interactive domain 1 alpha antibody at the left and (b) decreasing AT-rich interactive domain 1 alpha expression in another smooth muscle tumors of uncertain malignant potential at the right (DAB, ×200)

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   Discussion Top

Cav-1 protein has been documented in several neoplasms with a controversial role in cell proliferation, tumor development, and progression. This role is both complex and multifaceted. In some cell types, Cav-1 interacts with multiple members of the EGF-R/RAS/ERK and PI3/AKT pathways to modify signaling activity.[14] Previous studies showed that Cav-1 facilitates both ERK and AKT signaling in cancer cells from kidney, colon, prostate, epidermis, muscle, brain and is associated with promoting cell invasion, proliferation, angiogenesis, and multidrug resistance.[14],[15],[16],[17],[18],[19],[20] Most authors suggested that Cav-1 positive tumor cells served as tumor promoters by these signaling pathways.[5],[12],[14] We determined two different staining patterns for Cav-1 expressions. One of them was the cytoplasmic Cav-1 expression which was determined in the limited number of STUMPs while in the most LMSs. On the other hand, the perivascular expression of Cav-1 was almost always present in LMSs while absent in the most of STUMPs and all LMs. Although Cav-1 expression has been extensively studied in several carcinomas, there are little or no data on the expression and significance of Cav-1 in the uterine SMTs.[9],[10] Sendemir et al. demonstrated that Cav-1 is often expressed in LMs but does not appear in normal myometrial cells.[10] Consistent with the most published findings, we observed here that expression status of perivascular Cav-1 was changed according to the tumor aggressiveness. Statistically, we determined that if the tumor becomes higher grade, it gains the perivascular Cav-1 expression (P = 0.029).

The tumor microenvironment plays a crucial role in the initiation and progression of malignancies. It is now clear that cancer promotes increased microvessel density, recruits reactive stromal fibroblasts and different inflammatory cells, and releases peptide signaling molecules and proteases.[5],[21] Cancer-associated fibroblasts produce an altered extracellular matrix, which can induce epithelial-mesenchymal transition or other types of behaviors associated with a more aggressive phenotype in neighboring epithelial cells.[6] The exact mechanisms of this relationship are still largely unknown. Definition of expression status of Cav-1 in the peritumoral stromal cells has been accepted as a better parameter. In most English literature, stromal Cav-1 appears to be downregulated and the decreasing expression seems to play a negative role in cancer transformation. Many oncogenes such as SRC, RAS, and BCR-ABL, transcriptionally downregulate Cav-1 expression.[15],[16],[17],[18],[19],[20] Recent studies have focused their attention on Cav-1 expression in the peritumoral stromal cells rather than Cav-1 expression in the tumor cells.[21],[22],[23],[24] In this study, we could not evaluate Cav-1 expression in peritumoral uterine stroma, but perivascular Cav-1 expression within tumors consistent with the recent reports was associated with the malignancy of uterine SMTs. In addition, we determined a statistically significant association between the presence of perivascular Cav-1 expression and the absence of the nuclear ARID-1A expression. However, we could not provide an explanation about the impact of this relationship on the tumorigenesis of SMTs.

ARID-1A is a recently identified tumor suppressor gene that is mutated in a wide variety of gynecological and nongynecological cancers including ovarian, endometrial, and breast carcinomas.[11],[12],[13] Mutations in the ARID-1A gene are usually associated with loss of the ARID-1A encoded protein expression as assessed by IHC. Interestingly, mutations of the ARID-1A gene frequently co-occur with PI3K/AKT pathway activating mechanisms.[12] Some recent studies demonstrate an interdependency of ARID-1A and the PI3K/AKT pathway, which results in significantly increased sensitivity of ARID-1A deficient cancer cells to PI3K- and AKT-inhibition.[11],[12],[13],[25],[26],[27],[28],[29],[30],[31] The PI3K/AKT pathway has been highlighted as a potential promoter of LM growth in recent years.[32] It was demonstrated that phosphorylated AKT (p-AKT) levels are higher in LM tumors than matched myometrium. Tumors from menopausal women also showed reduced p-AKT levels compared to premenopausally derived tumors.[3] Therefore, it was suggested that the downstream signaling components of the PI3K/AKT pathway are involved in the survival and proliferation of LMs.[31],[32],[33] In the present study, we determined the expression defects of ARID-1A protein in benign SMTs. This finding was thought that the decreasing expression of ARID-1A may play a role in tumorigenesis in LM but not in malignant transformation.

   Conclusion Top

The results of our study demonstrate that altered expression of both Cav-1 and ARID-1A proteins may involve in tumorigenesis in the uterine SMTs. Therefore, it may be suggested that Cav-1 may act as a marker in these tumors, especially for differential diagnosis of the STUMPs and LMSs. Similarly, defects of ARID-1A gene may play a role on the development of LMs. However, our findings need further investigation in larger series.

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Conflicts of interest

There are no conflicts of interest.

   References Top

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Correspondence Address:
Dr. Gulden Diniz
Tepecik Training and Research Hospital, Kibris Sehitleri Caddesi 51/11 Alsancak, 35220, Izmir
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0377-4929.181891

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