Cancer-associated fibroblasts (CAFs) are abundant stromal cells in the tumor microenvironment that promote cancer progression and relapse. However, the heterogeneity and regulatory roles of CAFs underlying chemoresistance remain largely unclear. Here, we performed a single-cell analysis using high-dimensional flow cytometry analysis and identified a distinct senescence-like tetraspanin-8 (TSPAN8)⁺ myofibroblastic CAF (myCAF) subset, which is correlated with therapeutic resistance and poor survival in multiple cohorts of patients with breast cancer (BC). TSPAN8⁺ myCAFs potentiate the stemness of the surrounding BC cells through secretion of senescence-associated secretory phenotype (SASP)–related factors IL-6 and IL-8 to counteract chemotherapy. NAD-dependent protein deacetylase sirtuin 6 (SIRT6) reduction was responsible for the senescence-like phenotype and tumor-promoting role of TSPAN8⁺ myCAFs. Mechanistically, TSPAN8 promoted the phosphorylation of ubiquitin E3 ligase retinoblastoma binding protein 6 (RBBP6) at Ser⁷⁷² by recruiting MAPK11, thereby inducing SIRT6 protein destruction. In turn, SIRT6 down-regulation up-regulated GLS1 and PYCR1, which caused TSPAN8⁺ myCAFs to secrete aspartate and proline, and therefore proved a nutritional niche to support BC outgrowth. By demonstrating that TSPAN8⁺SIRT6^low myCAFs were tightly associated with unfavorable disease outcomes, we proposed that the combined regimen of anti-TSPAN8 antibody and SIRT6 activator MDL-800 is a promising approach to overcome chemoresistance. These findings highlight that senescence contributes to CAF heterogeneity and chemoresistance and suggest that targeting TSPAN8⁺ myCAFs is a promising approach to circumvent chemoresistance.

中文翻译：

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TSPAN8+肌纤维母细胞癌相关成纤维细胞促进乳腺癌患者的化疗耐药性

癌症相关成纤维细胞（CAF）是肿瘤微环境中丰富的基质细胞，可促进癌症进展和复发。然而，CAF 的异质性和调节作用在化疗耐药性中仍不清楚。在这里，我们使用高维流式细胞术进行了单细胞分析，并鉴定了一种独特的衰老样四跨蛋白-8 (TSPAN8) ⁺肌纤维母细胞 CAF (myCAF) 子集，该子集与多个队列中的治疗耐药性和较差的生存率相关。乳腺癌（BC）患者。 TSPAN8 ⁺ myCAF 通过分泌衰老相关分泌表型 (SASP) 相关因子 IL-6 和 IL-8 来增强周围 BC 细胞的干性，以对抗化疗。 NAD 依赖性蛋白脱乙酰酶 Sirtuin 6 (SIRT6) 的减少是 TSPAN8 ⁺ myCAF的衰老样表型和肿瘤促进作用的原因。从机制上讲，TSPAN8 通过招募 MAPK11 促进泛素 E3 连接酶视网膜母细胞瘤结合蛋白 6 (RBBP6) Ser ⁷⁷²的磷酸化，从而诱导 SIRT6 蛋白破坏。反过来，SIRT6 下调上调GLS1和PYCR1，导致 TSPAN8 ⁺ myCAF 分泌天冬氨酸和脯氨酸，因此被证明是支持 BC 生长的营养利基。通过证明 TSPAN8 ⁺ SIRT6^低myCAF 与不良疾病结果密切相关，我们提出抗 TSPAN8 抗体和 SIRT6 激活剂 MDL-800 的联合治疗方案是克服化疗耐药性的一种有前途的方法。这些发现强调衰老会导致 CAF 异质性和化疗耐药性，并表明靶向 TSPAN8 ⁺ myCAFs 是规避化疗耐药性的一种有前途的方法。