Positive staining of the immunoligand B7-H6 in abnormal/transformed keratinocytes consistently accompanies the progression of cervical cancer

Abstract

Background: B7-H6 has been revealed as an endogenous immunoligand expressed in a variety of tumors, but not expressed in healthy tissues. Heretofore, no studies have been reported describing B7-H6 in women with cervical cancer. To investigate this question, our present study was conducted.

Results: This retrospective study comprised a total of 62 paraffinized cervical biopsies, which were distributed in five groups: low-grade squamous intraepithelial lesions (LSIL), high-grade squamous intraepithelial lesions (HSIL), squamous cervical carcinoma (SCC), uterine cervical adenocarcinoma (UCAC), and a group of cervicitis (as a control for non-abnormal/non-transformed cells). Cervical sections were stained by immunohistochemistry to explore the expression of B7-H6, which was reported according to the immunoreactive score (IRS) system. We observed a complete lack of B7-H6 in LSIL abnormal epithelial cells. Interestingly, B7-H6 began to be seen in HSIL abnormal epithelial cells; more than half of this group had B7-H6 positive cells, with staining characterized by a cytoplasmic and membranous pattern. B7-H6 in the SCC group was also seen in the majority of the sections, showing the same cytoplasmic and membranous pattern. Strong evidence of B7-H6 was notably found in UCAC tumor columnar cells (in 100% of the specimens, also with cytoplasmic and membranous pattern). Moreover, consistent B7-H6 staining was observed in infiltrating plasma cells in all groups.

Conclusions: B7-H6 IRS positively correlated with disease stage in the development of cervical cancer; additionally, B7-H6 scores were found to be even higher in the more aggressive uterine cervical adenocarcinoma, suggesting a possible future therapeutic target for this cancer type.

Keywords: B7-H6; B7H6; Cervical cancer; Cervical intraepithelial lesions; NKp30; Therapeutic target.

Fig. 1

Representative immunohistochemical staining pattern of B7-H6 in cervical precancerous lesions and invasive cervical cancer. Specimens were categorized as follows: (a) ovarian cystadenoma (as the positive control): B7-H6 is mainly expressed in lining epithelium; (b) cervicitis: absence of B7-H6 in keratinocytes; (c) LSIL: absence of B7-H6 in abnormal keratinocytes; (d) HSIL: presence of B7-H6 in abnormal keratinocytes; (e) SCC: B7-H6 expression in transformed tumoral cells; (f) UCAC: strong expression of B7-H6 in transformed tumoral cells. Positive staining of B7-H6 is seen in the cytoplasm and membrane of transformed cells, and in plasma cells and mononuclear cells infiltrating the stroma. Photomicrographs were taken with different objectives (10x, 20x, and 40x). Abbreviations: LSIL: low-grade squamous intraepithelial lesion; HSIL: high-grade squamous intraepithelial lesion; SCC: squamous cervical carcinoma; UCAC: uterine cervical adenocarcinoma

Fig. 2

B7-H6 positivity according to the immunoreactive score in abnormal/transformed cells in cervical precancerous lesions and invasive cervical cancer. The results show a strong positive correlation coefficient between B7-H6 positivity and stage of the disease (LSIL, HSIL, and SCC) (ρ = 0.456), and a significance of p = 0.002. HSIL and both cervical cancer types present significant statistical differences when compared against LSIL. HSIL vs LSIL (p < 0.0005), SCC vs LSIL (p = 0.001) and UCAC vs LSIL (p < 0.0005). No significant differences were found between HSIL and SCC scores, but significance was found when comparing HSIL vs UCAC (p = 0.008), and SCC vs UCAC (p = 0.023). Abbreviations: LSIL: low-grade squamous intraepithelial lesion; HSIL: high-grade squamous intraepithelial lesion; SCC: squamous cervical carcinoma; UCAC: uterine cervical adenocarcinoma. ****p < 0.0005, ***p = 0.001, *p < 0.05

Fig. 3

B7-H6 immunoreactivity in plasma cells. B7-H6 positivity shows a cytoplasmic and membranous pattern in plasma cells. Photomicrographs were taken with different objectives (10x, 20x, 40x, and 63x) from a cervicitis sample. Positivity in plasma cells was considered as an internal control for the evaluation of B7-H6 staining in other cells

Fig. 4

B7-H6 positive staining according to the immunoreactive score in plasma cells infiltrating cervical intraepithelial lesions or invasive cancer. B7-H6 positivity in plasma cells is positively correlated with disease stage, confirmed by low staining in the intraepithelial lesion groups and stronger B7-H6 staining in the cancer groups. Statistically significant differences when comparing LSIL vs SCC (p = 0.001) and LSIL vs UCAC (p = 0.026) were found. As a control of non-abnormal or non-transformed cells, cervicitis specimens were also assessed. This group showed higher B7-H6 positive staining when compared against LSIL (p = 0.001). A positive correlation of B7-H6 staining between plasma cells and stage of the disease (LSIL, HSIL, and SCC) was found with ρ = 0.515 and a significance of p < 0.0005. Abbreviations: LSIL: low-grade squamous intraepithelial lesion; HSIL: high-grade squamous intraepithelial lesion; SCC: squamous cervical carcinoma; UCAC: uterine cervical adenocarcinoma. ***p = 0.001, *p < 0.05

Fig. 5

B7-H6 staining in mononuclear cells. All mononuclear cells with positive staining show cytoplasmic and membranous patterns. There are no differences in IRS, among the groups analyzed. Photomicrographs were taken with different objectives (10x, 20x, 40x, and 63x) from a chronic follicular cervicitis sample

Fig. 6

B7-H6 positive staining according to the immunoreactive score in mononuclear cells infiltrating cervical intraepithelial lesions or invasive cancer. Immunoreactivity for B7-H6 is higher in mononuclear cells of the cervicitis group, compared with the HSIL group (p = 0.043). Cervicitis specimens were used as control for non-abnormal or non-transformed cells. Abbreviations: LSIL: low-grade squamous intraepithelial lesion; HSIL: high-grade squamous intraepithelial lesion; SCC: squamous cervical carcinoma; UCAC: uterine cervical adenocarcinoma. *p < 0.05