Ototoxicity is traditionally viewed as a local cochlear adverse effect of indispensable therapies such as cisplatin and aminoglycosides. However, emerging evidence suggests that cochlear vulnerability is shaped by systemic physiology, including inflammatory tone, vascular barrier integrity, and metabolic state. In this Review, we propose a Gut–Mito–Ear axis in which gut ecosystem function influences circulating mediator modules that converge on two cochlear mediator nodes: blood–labyrinth barrier (BLB) gating and mitochondrial stress tolerance. We synthesize evidence showing that gut perturbation can alter cochlear outcomes in vivo, that at least one microbiota-derived metabolite signal can directly protect hearing in experimental settings, and that BLB dysfunction and inflammatory trafficking are mechanistically relevant to cisplatin- and aminoglycoside-induced injury. We further organize the literature using an evidence-weighted framework that distinguishes direct cochlear causality from mechanistic plausibility and explicitly retains negative studies as boundary-setting evidence. Finally, we outline a translational roadmap in which microbiome-targeted prevention is pursued through mediator-anchored, non-interference-aware strategies and evaluated across linked state variables spanning exposure context, gut function, defined mediator modules, BLB gating, mitochondrial stress tolerance, and auditory phenotype. The Gut–Mito–Ear axis is not considered an established mechanism. We present it as a falsifiable systems-biology model that organizes the current evidence. Within this model, we define the minimum and ideal standards for A-tier causal evidence, explicit criteria for interpreting boundary-setting negative (A−) studies, and a set of testable predictions for causal validation.

NRF2 (nuclear factor erythroid 2-related factor 2) and its repressor KEAP1 (Kelch-like ECH-associated protein 1) govern the antioxidant response; their role in breast cancer is paradoxical: the same program that prevents malignant transformation can later drive survival and therapy resistance. We argue that this behavior is not a fixed switch but a continuum conditioned by molecular subtype, disease stage, and therapeutic context. Synthesizing primary mechanistic and clinical evidence, we find that NRF2 activation is predominantly non-mutational and that its pathological dependence is strongest not in triple-negative breast cancer (TNBC) as a whole but in a candidate redox-addicted subset—defined by nuclear NRF2 with reduced cytoplasmic KEAP1 protein, cystine/SLC7A11 reliance, and active ferroptosis defense. This subset is hypothesis-generating rather than validated: current support derives chiefly from a single tissue microarray cohort and cell-line studies, and the co-occurrence and prevalence of its features remain unestablished. NRF2-driven suppression of ferroptosis is one major, tractable mechanism of resistance among several. We frame these as directions for future research: no NRF2-directed intervention is ready for biomarker-guided selection, and systemic NRF2 inhibition risks on-target toxicity, because NRF2 also protects normal tissues from oxidative stress.

Thyroid cancer (TC) is the most common endocrine malignancy, with incidence increasing worldwide. Although most differentiated TCs have a favorable prognosis, radioiodine (RAI)-refractory differentiated thyroid cancer (DTC), BRAF inhibitor-resistant papillary thyroid cancer, and anaplastic thyroid cancer (ATC) remain major areas of unmet clinical need. The sirtuin (SIRT) family of NAD⁺-dependent enzymes has emerged as a multifaceted regulator of TC biology, with isoform-specific dichotomous roles: SIRT1, SIRT6, and SIRT7 act as tumor promoters through engagement of BRAF/MAPK, PI3K/AKT, epithelial–mesenchymal transition (EMT), and Hippo pathways, while SIRT3 and SIRT4 function as tumor suppressors via mitochondrial metabolic regulation. This review synthesizes recent developments that expand the therapeutic landscape: (i) the recognition that SIRT7 functions as a desuccinylase with preclinically identified oncogenic substrates, modifying KIF23 in ATC and LATS1 in PTC; (ii) the emerging roles of isoform-specific SIRT axes, including the NAMPT–SIRT1–PD-L1 axis, SIRT6-associated regulatory T-cell biology, and SIRT2 as a T-cell metabolic checkpoint, as determinants of immune microenvironment state and potential modulators of immune checkpoint inhibitor response; and (iii) the SIRT6–nuclear receptor coactivator 4 (NCOA4) ferritinophagy axis as a supported ferroptosis vulnerability in ATC, with potential but still hypothesis-generating relevance to dedifferentiated and RAI-refractory DTC. Importantly, the therapeutic logic for SIRT6 is disease-state-specific rather than contradictory: SIRT6 inhibition is rationalized in BRAF-driven aggressive PTC and DTC contexts where SIRT6 supports MAPK signaling, EMT, and ferroptosis resistance, whereas in SIRT6-high ATC, the same enzyme’s NCOA4-dependent ferritinophagy activity may instead be exploited to enhance ferroptosis sensitivity. We review the current SIRT modulator pharmacological toolkit—including EX-527, OSS_128167, and emerging SIRT7-selective inhibitors—and identify the substantial clinical translation gap, with no SIRT-targeted clinical trial yet conducted in TC, despite strong preclinical rationale. We outline biomarker-stratified combination strategies with BRAF/MEK inhibitors, multikinase inhibitors, immune checkpoint inhibitors, and ferroptosis inducers, prioritizing biomarker-driven preclinical validation and, where supported by efficacy and safety data, subsequent early-phase evaluation in BRAF V600E-mutant and SIRT6-high thyroid cancer. Sirtuins thus represent a mechanistically promising and potentially biomarker-stratifiable therapeutic hypothesis for difficult-to-treat thyroid cancer; however, clinical translation remains at an early stage and requires validated biomarkers, isoform-selective compounds, and disease-specific in vivo evidence.

Ototoxicity is traditionally viewed as a local cochlear adverse effect of indispensable therapies such as cisplatin and aminoglycosides. However, emerging evidence suggests that cochlear vulnerability is shaped by systemic physiology, including inflammatory tone, vascular barrier integrity, and metabolic state. In this Review, we propose a Gut–Mito–Ear axis in which gut ecosystem function influences circulating mediator modules that converge on two cochlear mediator nodes: blood–labyrinth barrier (BLB) gating and mitochondrial stress tolerance. We synthesize evidence showing that gut perturbation can alter cochlear outcomes in vivo, that at least one microbiota-derived metabolite signal can directly protect hearing in experimental settings, and that BLB dysfunction and inflammatory trafficking are mechanistically relevant to cisplatin- and aminoglycoside-induced injury. We further organize the literature using an evidence-weighted framework that distinguishes direct cochlear causality from mechanistic plausibility and explicitly retains negative studies as boundary-setting evidence. Finally, we outline a translational roadmap in which microbiome-targeted prevention is pursued through mediator-anchored, non-interference-aware strategies and evaluated across linked state variables spanning exposure context, gut function, defined mediator modules, BLB gating, mitochondrial stress tolerance, and auditory phenotype. Framed in this way, the Gut–Mito–Ear axis is presented not as an established mechanism but as an operational, falsifiable systems-biology model that defines minimum and ideal standards for A-tier evidence, interpretable criteria for boundary-setting A− evidence, and testable predictions for causal validation.