PD-L1-Expressing Radiation-Associated Angiosarcoma after Primary Breast Cancer

Sodium/glucose cotransporter 1-dependent metabolic alterations induce tamoxifen resistance in breast cancer by promoting macrophage M2 polarization

Endocrine therapy is the standard treatment for estrogen receptor (ER)-positive breast cancer, but tumors eventually develop resistance. However, endocrine therapy resistance mechanisms mediated through interactions between breast cancer cells and tumor-associated macrophages (TAMs) are still unclear. Here, we characterized sodium/glucose cotransporter 1 (SGLT1) overexpression drives the highly glycolytic phenotype of tamoxifen-resistant breast cancer cells where enhanced lactic acid secretion promotes M2-like TAM polarization via the hypoxia-inducible factor-1α/signal transducer and activator of transcription-3 pathway. In turn, M2-like TAMs activate breast cancer cells through EGFR/PI3K/Akt signaling, providing feedback to upregulate SGLT1 and promote tamoxifen resistance and accelerate tumor growth in vitro and in vivo. Higher expression of SGLT1 and CD163⁺ TAMs was associated with endocrine-resistant ER-positive breast cancers. Our study identifies a novel vicious cycle of metabolic reprogramming, M2-like TAM polarization, and endocrine therapy resistance, which involves SGLT1, proposing SGLT1 as a therapeutic target to overcome endocrine therapy resistance in breast cancer.

Histopathologic PD-L1 Tumor Expression and Prognostic Significance in Nonmelanoma Skin Cancers: A Systematic Review

ABSTRACT

PD-L1 and PD-1 inhibitors are being increasingly used to treat a variety of nonmelanoma skin cancers (NMSCs). This systematic review summarizes PD-L1 expression in NMSCs and determines its use for prognosis using targeted immunotherapy. A primary search of peer-reviewed English-language medical literature was conducted for studies on PD-L1 tumor expression in biopsied or excised NMSCs. Fifty-nine articles met criteria for inclusion. PD-L1 expression in advanced NMSCs ranged from 22%-89% for basal cell carcinomas, 42%-50% for Merkel cell carcinomas, and 26%-100% for squamous cell carcinomas. Study limitations included clone heterogeneity across studies, complicating comparison of PD-L1 expression. Differences were also noted in the selection of tumor reactivity threshold. We conclude that there is insufficient evidence to determine the prognostic significance of PD-L1 expression in NMSCs as a whole, but this remains a promising area. More investigation into the role of tumor PD-L1 as a biomarker for predicting clinical response to PD-L1 and PD-1 inhibitors in NMSCs is needed.

Microsatellite-Stable Radiation-Induced Angiosarcoma after Breast-Conserving Surgery: A Case Report

Radiation-induced angiosarcoma (RIAS) after breast-conserving surgery is quite rare. Risk factors for RIAS have yet to be identified, due largely to the very low incidence of this disease. The etiologic mechanisms of RIAS are not understood, although some reports suggest that genome instability may contribute to RIAS development. An 81-year-old Japanese woman presented to our hospital after developing multiple dark purple nodules on her left breast. She had undergone breast-conserving surgery for left breast cancer and adjuvant radiotherapy for the conserved breast 9 years earlier. Punch biopsy of one of the dark purple nodules was performed and the pathological diagnosis was angiosarcoma. She underwent total mastectomy with an adequate margin, and skin collected from her left thigh was grafted onto the site. Pathologically, the surgical margin was negative. The tumor was negative for microsatellite instability (MSI). Considering her age, she has remained under careful observation with neither systemic treatment nor adjuvant radiation. The only standard therapy for RIAS currently available is complete resection. Hence, early detection is crucial to obtain an adequate margin, followed by careful observation after breast-conserving surgery. It is also essential to reveal the tumor etiology, and for that purpose, we believe that the MSI status may be beneficial for the further investigation of RIAS.