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BackgroundNovel biomarkers are required to discern between breast tumors that should be targeted for treatment from those that would never become clinically apparent and/or life threatening for patients. Moreover, therapeutics that specifically target breast cancer (BC) cells with tumor-initiating capacity to prevent recurrence are an unmet need. We investigated the clinical importance of LGR5 in BC and ductal carcinoma in situ (DCIS) to explore LGR5 as a biomarker and a therapeutic target.MethodsWe stained BC (n = 401) and DCIS (n = 119) tissue microarrays with an antibody against LGR5. We examined an LGR5 knockdown ER- cell line that was orthotopically transplanted and used for in vitro colony assays. We also determined the tumor-initiating role of Lgr5 in lineage-tracing experiments. Lastly, we transplanted ER- patient-derived xenografts into mice that were subsequently treated with a LGR5 antibody drug conjugate (anti-LGR5-ADC).ResultsLGR5 expression correlated with small tumor size, lower grade, lymph node negativity, and ER-positivity. ER+ patients with LGR5high tumors rarely had recurrence, while high-grade ER- patients with LGR5high expression recurred and died due to BC more often. Intriguingly, all the DCIS patients who later died of BC had LGR5-positive tumors. Colony assays and xenograft experiments substantiated a role for LGR5 in ER- tumor initiation and subsequent growth, which was further validated by lineage-tracing experiments in ER- /triple-negative BC mouse models. Importantly, by utilizing LGR5high patient-derived xenografts, we showed that anti-LGR5-ADC should be considered as a therapeutic for high-grade ER- BC.ConclusionLGR5 has distinct roles in ER- vs. ER+ BC with potential clinical applicability as a biomarker to identify patients in need of therapy and could serve as a therapeutic target for high-grade ER- BC.

Abstract Background Microarray gene-profiling of invasive breast cancer has identified different subtypes including luminal A, luminal B, HER2-overexpressing and basal-like groups. Basal-like invasive breast cancer is associated with a worse prognosis. However, the prognosis of basal-like ductal carcinoma in situ (DCIS) is still unknown. Our aim was to study the prognosis of basal-like DCIS in a large population-based cohort. Methods All 458 women with a primary DCIS diagnosed between 1986 and 2004, in Uppland and Västmanland, Sweden were included. TMA blocks were constructed. To classify the DCIS tumors, we used immunohistochemical (IHC) markers (estrogen-, progesterone-, HER2, cytokeratin 5/6 and epidermal growth factor receptor) as a surrogate for the gene expression profiling. The association with prognosis was examined for basal-like DCIS and other subtypes using Kaplan-Meier survival analyses and Cox proportional hazards regression models. Results IHC data were complete for 392 women. Thirty-two were basal-like (8.2%), 351 were luminal or HER2-positive (89.5%) and 9 unclassified (2.3%). Seventy-six women had a local recurrence of which 34 were invasive. Another 3 women had general metastases as first event. Basal-like DCIS showed a higher risk of local recurrence and invasive recurrence 1.8 (Confidence interval (CI) 95%, 0.8-4.2) and 1.9 (0.7-5.1), respectively. However, the difference was not statistically significant. Also, no statistically significant increased risk was seen for triple-negative or high grade DCIS. Conclusions Basal-like DCIS showed about a doubled, however not statistically significant risk for local recurrence and developing invasive cancer compared with the other molecular subtypes. Molecular subtyping was a better prognostic parameter than histopathological grade.

Background Different molecular subtypes of breast cancer have been identified based on gene expression profiling. Treatment suggestions based on an approximation of these subtypes by immunohistochemical criteria have been published by the St Gallen international expert consensus panel. Ductal carcinoma in situ (DCIS) can be classified into the same molecular subtypes. Our aim was to study the relation between these newly defined subtypes and prognosis in DCIS. Methods TMA including 458 women from a population-based cohort with DCIS diagnosed 1986-2004 was used. Stainings for ER, PR, HER2 and Ki67 were used to classify the surrogate molecular subtypes according to the St Gallen criteria from 2011. The associations with prognosis were examined using Kaplan-Meier analyses and Cox proportional hazards regression models. Results Surrogate molecular subtyping could be done in 381 cases. Mean follow up was 164 months. Of the classified DCIS 186 were Luminal A (48.8%), 33 Luminal B/HER2- (8.7%), 74 Luminal B/HER2+ (17.4%), 61 HER2+/ER- (16.0%) and 27 Triple Negative (7.1%). One hundred and two women had a local recurrence of which 58 were invasive. Twenty-two women had generalised disease, 8 without a prior local recurrence. We could not find a prognostic significance of the molecular subtypes other than a higher risk of developing breast cancer after more than 10 years of follow-up among women with a Triple Negative DCIS (OR 3.2; 95% CI 1.1-9.8). Conclusions The results from this large population-based cohort, with long-term follow up failed to demonstrate a prognostic value for the surrogate molecular subtyping of DCIS using the St Gallen criteria up to ten years after diagnosis. More than ten years after diagnosis Triple Negative DCIS had an elevated risk of recurrence. [ABSTRACT FROM AUTHOR]

Background: Microarray gene-profiling of invasive breast cancer has identified different subtypes including luminal A, luminal B, HER2-overexpressing and basal-like groups. Basal-like invasive breast cancer is associated with a worse prognosis. However, the prognosis of basal-like ductal carcinoma in situ (DCIS) is still unknown. Our aim was to study the prognosis of basal-like DCIS in a large population-based cohort. Methods: All 458 women with a primary DCIS diagnosed between 1986 and 2004, in Uppland and Västmanland, Sweden were included. TMA blocks were constructed. To classify the DCIS tumors, we used immunohistochemical (IHC) markers (estrogen-, progesterone-, HER2, cytokeratin 5/6 and epidermal growth factor receptor) as a surrogate for the gene expression profiling. The association with prognosis was examined for basal-like DCIS and other subtypes using Kaplan-Meier survival analyses and Cox proportional hazards regression models. Results: IHC data were complete for 392 women. Thirty-two were basal-like (8.2%), 351 were luminal or HER2- positive (89.5%) and 9 unclassified (2.3%). Seventy-six women had a local recurrence of which 34 were invasive. Another 3 women had general metastases as first event. Basal-like DCIS showed a higher risk of local recurrence and invasive recurrence 1.8 (Confidence interval (CI) 95%, 0.8-4.2) and 1.9 (0.7-5.1), respectively. However, the difference was not statistically significant. Also, no statistically significant increased risk was seen for triple-negative or high grade DCIS. Conclusions: Basal-like DCIS showed about a doubled, however not statistically significant risk for local recurrence and developing invasive cancer compared with the other molecular subtypes. Molecular subtyping was a better prognostic parameter than histopathological grade. [ABSTRACT FROM AUTHOR]