Interleukin-8 (IL-8/CXCL8) drives tumor progression via CXCR1/2 signaling, promoting proliferation, invasion, angiogenesis, and recruitment of pro-tumoral immune and stromal cells. Accumulating clinical evidence indicates that elevated circulating or intratumoral IL-8 levels are consistently associated with adverse prognosis and reduced therapeutic benefit across principal solid tumors. In particular, IL-8 has emerged as a promising prognostic and predictive biomarker of resistance to immune checkpoint inhibitors. This review highlights its prognostic and predictive value across gastrointestinal, genitourinary, lung, melanoma, breast, ovarian, and head and neck cancers, and discusses strategies targeting IL-8 and the need for standardized, clinically actionable assays.

Mechanistic relationships between heat shock protein 90 (HSP90) and human epidermal growth factor receptor 2 (HER2) are complex and clinical correlations in breast cancer remain inconsistent. We investigated the role of HSP90 expression in the response of breast cancer cells to HER2-targeted treatments, by measuring cell viability/proliferation and protein expression after genetic and pharmacologic HER2/HSP90 modulation. HSP90 expression was also assessed by immunohistochemistry in a series of 72 metastatic, HER2+ breast cancer patients. In HER2+ breast cancer models (AU565, BT474, MCF7-HER2), HER2 downregulation induced HSP90 upregulation and growth inhibitory synergism between trastuzumab and docetaxel. HSP90 downregulation blunted the response to trastuzumab and docetaxel and their synergistic interactions. The addition of pertuzumab caused little additional growth inhibition, but HSP90 silencing unmasked a synergistic growth inhibitory effect with the triple combination. Conversely, HSP90 downregulation blunted the therapeutic response to trastuzumab/pertuzumab/tamoxifen or trastuzumab–emtansine. In HER2+ breast cancer patients, high HSP90 expression was associated with significant progression-free survival benefit with the triple combination, as compared with trastuzumab and chemotherapy, although the interaction test was not statistically significant. Overall, our results highlight a mechanistic role for HSP90 in determining the response of breast cancer cells to HER2-targeted agents and suggest that trastuzumab/pertuzumab combinations may be particularly advantageous in HSP90-high, HER2+ breast cancer.

Leptomeningeal carcinomatosis is a rare but serious consequence of pre-existing tumors, such as breast, lung, and gastrointestinal carcinomas. Further, leptomeningeal carcinomatosis is more frequently diagnosed with breast cancers, if only because breast cancers are diagnosed far more often than any other carcinomas. In this paper, we present the case of a leptomeningeal carcinomatosis patient who experienced complete remission following therapy targeted at the Her-2 (human epidermal growth factor receptor 2-positive) receptor. This patient’s diagnosis was complicated by the fact that brain and column MRI imaging were clear, but analysis of the cerebrospinal fluid led to the conclusion of leptomeningeal carcinomatosis. The tests were requested because the patient, under chemotherapy for advanced breast cancer at the time, reported some neurological symptoms. Following the diagnosis of leptomeningeal carcinomatosis and subsequent T-DM1 Her-2 receptor therapy, the patient showed a complete response to leptomeningeal carcinomatosis within 30 days and survived for another 16 months. This case offers compelling evidence that the effect TDM1 Her-2 receptor therapy has on a patient’s remission and long-term survivability is considerably better than other therapies for similar pre-existing conditions diagnosed with leptomeningeal carcinomatosis. Further prospective studies should confirm these findings.