Probes for INS

PURPOSE:

RNA expression of androgen receptor splice variants may be a biomarker of resistance to novel androgen deprivation therapies in castrate resistant prostate cancer (CRPC). We analytically validated an RNA in situ hybridization (RISH) assay for total AR and AR-V7 for use in formalin fixed paraffin embedded (FFPE) prostate tumors.

EXPERIMENTAL DESIGN:

We used prostate cell lines and xenografts to validate chromogenic RISH to detect RNA containing AR exon 1 (AR-E1, surrogate for total AR RNA species) and cryptic exon 3 (AR-CE3, surrogate for AR-V7 expression). RISH signals were quantified in FFPE primary tumors and CRPC specimens, comparing to known AR and AR-V7 status by immunohistochemistry and RT-PCR.

RESULTS:

The quantified RISH results correlated significantly with total AR and AR-V7 levels by RT-PCR in cell lines, xenografts and autopsy metastases. Both AR-E1 and AR-CE3 RISH signals were localized in nuclear punctae in addition to the expected cytoplasmic speckles. Compared to admixed benign glands, AR-E1 expression was significantly higher in primary tumor cells with a median fold increase of 3.0 and 1.4 in two independent cohorts (p<0.0001 and p=0.04, respectively). While AR-CE3 expression was detectable in primary prostatic tumors, levels were substantially higher in a subset of CRPC metastases and cell lines, and were correlated with AR-E1 expression.

CONCLUSIONS:

RISH for AR-E1 and AR-CE3 is an analytically valid method to examine total AR and AR-V7 RNA levels in FFPE tissues. Future clinical validation studies are required to determine whether AR RISH is a prognostic or predictive biomarker in specific clinical contexts.

Introduction

Pre-clinically, high FGFR1 mRNA (FGFR1-MRNA) and FGFR1 amplification (FGFR1-AMP) predicted sensitivity to FGFR inhibitors in NSCLC and SCLC cell lines. KRAS mutations did not preclude sensitivity.

Patients and Methods

Metastatic EGFR- and ALK-negative lung cancers were screened for FGFR1-MRNA by in-situ hybridization (ISH) and FGFR1-AMP by silver in-situ hybridization (SISH). Positive cases were offered ponatinib, a multi-kinase inhibitor of FGFR1-4. Differences in overall survival (OS) between cohorts were assessed using log-rank test. Association of FGFR1 positivity with clinicopathologic features were assessed using Fisher’s exact test and Kruskal-Wallis rank sum test.

Results

171 cases were prescreened: 9/123 (7.3%) SISH+; 53/126 (42.1%) ISH+; 6 cases concordantly positive for SISH and ISH. SISH+ cases had fewer coincident KRAS mutations (p=0.03) than SISH- cases, and ISH+ cases had worse OS (p=0.020) than ISH- cases. Data distributions suggested a distinct higher positivity cutpoint for FGFR1 ISH (≥20%), occurring in 23% [29/126] cases, was associated with SCLC histology (p=0.022), soft tissue metastases (p=0.050) and shorter OS (p=0.031). Four patients received ponatinib on study: All ISH+ by the initial cutpoint, 2/4 by higher cutpoint, 1/4 SISH+. Tolerability was poor. The best response for the two higher ISH cases was SD and PD for the two lower ISH cases.

Conclusions

Elevated FGFR1-MRNA is more common than FGFR1-AMP and associated with worse OS. Higher FGFR1 mRNA expression may be associated with a specific phenotype and is worthy of further exploration. Ponatinib’s poor tolerance suggests further FGFR exploration in ISH+ cases should utilize more selective FGFR1 inhibitors.

BACKGROUND:

Fibroblast growth factor receptor 1 (FGFR1) amplification is a potential driving oncogene in squamous cell cancer (SCC) of the lung. The current phase 2 study evaluated the efficacy and tolerability of dovitinib, an FGFR inhibitor, in patients with advanced SCC of the lung.

METHODS:

Patients with pretreated advanced SCC of the lung whose tumors demonstrated FGFR1 amplification of > 5 copies by fluorescence in situ hybridization were enrolled. Dovitinib at a dose of 500 mg was administered orally, once daily, on days 1 to 5 of every week, followed by 2 days off. The primary endpoint was overall response. Secondary endpoints were progression-free survival, overall survival, and toxicity.

RESULTS:

All 26 patients were men with a median age of 68 years (range, 52-80 years). The majority of patients were ever-smokers. The median duration of dovitinib administration (28 days per cycle) was 2.5 months (range, 0.7-8.6 months). The overall response rate was 11.5% (95% confidence interval [95% CI], 0.8%-23.8%) and the disease control rate was 50% (95% CI, 30.8%-69.2%), with 3 patients achieving partial responses. Response durations for the patients with partial responses were ≥4.5 months, ≥ 5.1 months, and 6.1 months, respectively. After a median follow-up of 15.7 months (range, 1.2-25.6 months), the median overall survival was 5.0 months (95% CI, 3.6-6.4 months) and the median progression-free survival was 2.9 months (95% CI, 1.5-4.3 months). The most common grade 3 or higher adverse events were fatigue (19.2%), anorexia (11.5%), and hyponatremia (11.5%) (event severity was graded based on National Cancer Institute Common Terminology Criteria for Adverse Events [version 4.0]).