Basal biomarkers nestin and INPP4B predict gemcitabine benefit in metastatic breast cancer: Samples from the phase III SBG0102 clinical trial.

In a formal prospective-retrospective analysis of the phase III SBG0102 clinical trial randomizing metastatic breast cancer patients to gemcitabine-docetaxel or to single agent docetaxel, patients with basal-like tumors by PAM50 gene expression had significantly better overall survival in the gemcitabine arm. By immunohistochemistry (IHC), triple negative status was not predictive, but more specific biomarkers have since become available defining basal-like by nestin positivity or loss of inositol-polyphosphate-4-phosphate (INPP4B). Here, we evaluate their capacity to identify which patients benefit from gemcitabine in the metastatic setting. Nestin and INPP4B staining and interpretation followed published methods. A prespecified statistical plan evaluated the primary hypothesis that patients with basal-like breast cancer, defined as "nestin+ or INPP4B-", would have superior overall survival on gemcitabine-docetaxel when compared to docetaxel. Interaction tests, Kaplan-Meier curves and forest plots were used to assess prognostic and predictive capacities of biomarkers relative to treatment. Among 239 cases evaluable for our study, 36 (15%) had been classified as basal-like by PAM50. "Nestin+ or INPP4B-" was observed in 41 (17%) of the total cases and was significantly associated with PAM50 basal-like subtype. Within an estimated median follow-up of 13 years, patients assigned as IHC basal "nestin+ or INPP4B-" had significantly better overall survival on gemcitabine-docetaxel versus docetaxel monotherapy (HR = 0.31, 95%CI: 0.16-0.60), whereas no differences were observed for other patients (HR = 0.99), p-interaction < 0.01. In the metastatic setting, women with IHC basal breast cancers defined as "nestin+ or INPP4B-" have superior overall survival when randomized to gemcitabine-containing chemotherapy compared to docetaxel alone. These findings need to be validated using larger prospective-retrospective phase III clinical trials series.

Nestin expression in breast cancer: association with prognosis and subtype on 3641 cases with long-term follow-up.

BACKGROUND: Basal-like breast cancers, originally recognized by gene expression profiling, can be clinically identified using immunohistochemical (IHC) definitions that require estrogen receptor (ER) negativity. However, some basal cases are ER positive and are mistakenly considered to be luminal by standard IHC approaches, leading to suboptimal treatment choices. Nestin, an intermediate filament expressed in many stem cells, is a recently identified positive marker of basal-like phenotype independent of ER status. In this study, we evaluated its clinical associations and prognostic capacity in a large breast cancer cohort. METHODS: A tissue microarray series of clinically annotated invasive breast cancers with 12.6-year median follow-up was assessed for nestin expression by IHC. Kaplan-Meier and Cox regression models were used to evaluate the prognostic significance of nestin status, for the primary endpoint of breast cancer-specific survival (BCSS). RESULTS: Among 3641 cases interpretable for nestin by IHC, positive staining was found in 371 cases (10%) and was significantly associated with poor prognostic factors including other markers of basal-like differentiation. Patients with nestin-positive tumors had a significantly lower 10 year BCSS (HR 1.97, 95% CI 1.62-2.40; P < 0.001). Importantly, within the large group of 2323 ER+ cases, nestin positivity identified a subgroup of 120 patients (5%) with a significantly inferior 10-year BCSS (HR 1.50, 95% CI 1.10-2.13; P = 0.02). CONCLUSIONS: Nestin IHC positivity is associated with the poor clinical outcomes and reduced survival rates that characterize the gene expression basal-like subtype. This easily applicable tool identifies ER+ poor prognosis basal phenotype patients that are currently being missed by "Triple negative" or "Core basal" IHC definitions.

Basal biomarkers nestin and INPP4b identify intrinsic subtypes accurately in breast cancers that are weakly positive for oestrogen receptor.

AIMS: Recent evidence indicates that weakly positive immunohistochemical staining of oestrogen receptor (ER) is not associated reliably with a luminal subtype, with the majority reclassified as basal-like by gene expression profile. In this study we assessed the capacity of recently identified immunohistochemical markers of basal-like subtype not dependent upon ER status - positive expression of nestin or loss of inositol polyphosphate-4-phosphatase (INPP4b) - to discriminate intrinsic subtypes, focusing on clinically problematic cases with weak ER positivity. METHODS AND RESULTS: Formalin-fixed paraffin-embedded blocks, enriched for large proportions of ER-negative and ER weakly positive breast cancers, were selected from two previous studies conducted in the period 2008-13 and used for (i) RNA extraction for 50-gene subtype predictor (PAM50) intrinsic subtyping and (ii) tissue microarray construction for immunohistochemical assessment of nestin and INPP4b. Fifty-eight cases were weakly positive for ER (Allred 3-5), among which 28 (48%) were assigned as basal-like by PAM50 gene expression. In these 58 cases, the nestin/INPP4b panel identified 23 basal-like cases with a positive predictive value of 87% [95% confidence interval (CI) 78-95%] and excluded luminal subtype with a negative predictive value of 95% (95% CI 88-100%). Weakly positive ER patients assigned as basal-like by nestin/INPP4b definition demonstrated a median survival time of 45.8 months, significantly lower than 65 months among other ER weakly positive cases (P = 0.012). CONCLUSIONS: Immunohistochemical assessment of nestin and INPP4b provides an accurate, accessible and inexpensive tool to identify basal-like breast cancer subtype in the clinically problematic setting of weak ER positivity. This panel identifies poor prognosis patients who might need strong considerations for non-endocrine-based therapies.

Quantitative Detection and Resolution of BRAF V600 Status in Colorectal Cancer Using Droplet Digital PCR and a Novel Wild-Type Negative Assay.

A need exists for robust and cost-effective assays to detect a single or small set of actionable point mutations, or a complete set of clinically informative mutant alleles. Knowledge of these mutations can be used to alert the clinician to a rare mutation that might necessitate more aggressive clinical monitoring or a personalized course of treatment. An example is BRAF, a (proto)oncogene susceptible to either common or rare mutations in codon V600 and adjacent codons. We report a diagnostic technology that leverages the unique capabilities of droplet digital PCR to achieve not only accurate and sensitive detection of BRAF(V600E) but also all known somatic point mutations within the BRAF V600 codon. The simple and inexpensive two-well droplet digital PCR assay uses a chimeric locked nucleic acid/DNA probe against wild-type BRAF and a novel wild-type-negative screening paradigm. The assay shows complete diagnostic accuracy when applied to formalin-fixed, paraffin-embedded tumor specimens from metastatic colorectal cancer patients deficient for Mut L homologue-1.

A survey of immunohistochemical biomarkers for basal-like breast cancer against a gene expression profile gold standard.

Gene expression profiling of breast cancer delineates a particularly aggressive subtype referred to as 'basal-like', which comprises ∼15% of all breast cancers, afflicts younger women and is refractory to endocrine and anti-HER2 therapies. Immunohistochemical surrogate definitions for basal-like breast cancer, such as the clinical ER/PR/HER2 triple-negative phenotype and models incorporating positive expression for CK5 (CK5/6) and/or EGFR are heavily cited. However, many additional biomarkers for basal-like breast cancer have been described in the literature. A parallel comparison of 46 proposed immunohistochemical biomarkers of basal-like breast cancer was performed against a gene expression profile gold standard on a tissue microarray containing 42 basal-like and 80 non-basal-like breast cancer cases. Ki67 and PPH3 were the most sensitive biomarkers (both 92%) positively expressed in the basal-like subtype, whereas CK14, IMP3 and NGFR were the most specific (100%). Among biomarkers surveyed, loss of INPP4B (a negative regulator of phosphatidylinositol signaling) was 61% sensitive and 99% specific with the highest odds ratio (OR) at 108, indicating the strongest association with basal-like breast cancer. Expression of nestin, a common marker of neural progenitor cells that is also associated with the triple-negative/basal-like phenotype and poor breast cancer prognosis, possessed the second highest OR at 29 among the 46 biomarkers surveyed, as well as 54% sensitivity and 96% specificity. As a positively expressed biomarker, nestin possesses technical advantages over INPP4B that make it a more ideal biomarker for identification of basal-like breast cancer. The comprehensive immunohistochemical biomarker survey presented in this study is a necessary step for determining an optimized surrogate immunopanel that best defines basal-like breast cancer in a practical and clinically accessible way.