High serum levels of IL-6 correlate with poor outcome in breast cancer patients. However, no data are available on the relationship between IL-6 and mammary stem/progenitor cells, which may fuel the genesis of breast cancer in vivo. Herein, we address this issue in the MCF-7 breast cancer cell line and in primary human mammospheres (MS), multicellular structures enriched in stem/progenitor cells of the mammary gland. MS from node invasive breast carcinoma tissues expressed IL-6 mRNA at higher levels than did MS from matched non-neoplastic mammary glands. In addition, IL-6 mRNA was detected only in basal-like breast carcinoma tissues, an aggressive breast carcinoma variant showing stem cell features. IL-6 treatment triggered Notch-3–dependent upregulation of the Notch ligand Jagged-1 and promotion of MS and MCF-7–derived spheroid growth. Moreover, IL-6 induced Notch-3–dependent upregulation of the carbonic anhydrase IX gene and promoted a hypoxia-resistant/invasive phenotype in MCF-7 cells and MS. Finally, autocrine IL-6 signaling relied upon Notch-3 activity to sustain the aggressive features of MCF-7–derived hypoxia-selected cells. In conclusion, these data support the hypothesis that IL-6 induces malignant features in Notch-3–expressing stem/progenitor cells from human ductal breast carcinoma and normal mammary gland.

We have investigated the importance of interleukin-6 (IL-6) in promoting tumor growth and metastasis. In human primary breast cancers, increased levels of IL-6 were found at the tumor leading edge and positively correlated with advanced stage, suggesting a mechanistic link between tumor cell production of IL-6 and invasion. In support of this hypothesis, we showed that the IL-6/Janus kinase (JAK)/signal transducer and activator of transcription 3 (Stat3) pathway drives tumor progression through the stroma and metastatic niche. Overexpression of IL-6 in tumor cell lines promoted myeloid cell recruitment, angiogenesis, and induced metastases. We demonstrated the therapeutic potential of interrupting this pathway with IL-6 receptor blockade or by inhibiting its downstream effectors JAK1/2 or Stat3. These clinically relevant interventions did not inhibit tumor cell proliferation in vitro but had profound effects in vivo on tumor progression, interfering broadly with tumor-supportive stromal functions, including angiogenesis, fibroblast infiltration, and myeloid suppressor cell recruitment in both the tumor and pre-metastatic niche. This study provides the first evidence for IL-6 expression at the leading edge of invasive human breast tumors and demonstrates mechanistically that IL-6/JAK/Stat3 signaling plays a critical and pharmacologically targetable role in orchestrating the composition of the tumor microenvironment that promotes growth, invasion, and metastasis.

Background: The purpose of this phase II study was to evaluate the efficacy and safety of cetuximab combined with FOLFIRI as a first-line treatment of advanced gastric or gastroesophageal junction (GEJ) adenocarcinoma. Patients and methods: Untreated patients with confirmed advanced gastric or gastroesophageal adenocarcinoma received cetuximab at an initial dose of 400 mg/m² intravenously (i.v.) followed by weekly doses of 250 mg/m², CPT 11 180 mg/m² i.v. on day 1, LFA 100 mg/m² i.v. followed by 5-FU 400 mg/m² i.v. bolus, and 600 mg/m² i.v. 22-h continuous infusion on days 1 and 2 (FOLFIRI) every 2 weeks, for a maximum of 24 weeks, then cetuximab alone was allowed in patients with a complete response, partial response, or stable disease. Antitumor activity was assessed by computed tomography (CT) and positron emission tomography (PET) at baseline and after 6 weeks, and further by CT alone or CT and PET every 6 weeks. Results: Thirty-eight patients were enrolled (median age 63.5 years, range 39–83; median Karnofsky performance status 90, range 70–100; stomach 89.5% and GEJ 10.5%; locally advanced disease 13.2% and metastatic disease 86.8%). All 38 patients were assessed for safety and survival, and 34 patients were assessed for overall response rates (ORR). The ORR was 44.1% [95% confidence interval (CI) 27.5% to 60.9%]. The median time-to-progression was 8 months (95% CI 7–9). At the median follow-up time of 11 months, 55.3% of patients were alive, with a median expected survival time of 16 months (95% CI 9–23). Grade 3–4 toxicity included neutropenia (42.1%), acne-like rash (21.1%), diarrhea (7.9%), asthenia (5.3%), stomatitis (5.3%), and hypertransaminasemia (5.3%). There was one (2.6%) treatment-related death. Conclusions: The combination of cetuximab and FOLFIRI is active in gastric and GEJ adenocarcinoma. The higher toxicity appears to be limited to neutropenia.