The data reported herein, show that: 1) FGFR-1 amplification is observed in a subset of lymph-nodal and haematogenous metastases from lobular breast carcinoma; 2) minor heterogeneity is scored in matched primary and metastatic lobular breast carcinomas; 3) in the era of tailored therapies, patients affected by the lobular subtype of breast carcinoma with FGFR-1 amplification may be considered a potential patients’ subset benefiting from FGFR-1 inhibitor.
The efficacy use of endocrine therapies for hormone receptor-positive breast cancer and trastuzumab and lapatinib for targeting HER2-positive tumors has placed the way for the clinical development of other metastatic breast cancer targeted therapies. Conversely, the benefit of anti-VEGF (vascular endothelial growth factor) monoclonal antibody in the metastatic setting, is still under investigation, as well as new HER2-targeted agents and VEGF-targeted agents, dual epidermal growth factor receptor/HER2-targeted agents, multitargeted tyrosine kinase inhibitors, and mammalian target of rapamycin and poly (ADP-ribose) polymerase 1 inhibitors. These anticancer agents are being tested in clinical trials with the potential of addressing unmet therapeutic needs in the metastatic patient population.
In the breast cancer scenario, Massabeau et al. evaluated the role of FGFR1 and its ligand, the fibroblast growth factor 2 in determining the response to chemoradiotherapy. Among the low/intermediate grade tumors, FGFR-1 negative tumors did not respond to chemoradiotherapy, compared with tumors expressing FGFR-1 among which, almost one half had a good response. Among the low and intermediate grade breast cancers, the FGFR-1 negative tumors were resistant to chemoradiotherapy. They concluded that the expression of FGFR-1 in patients’ biopsies may serve as a marker of response to chemoradiotherapy. Turner et al. concluded that amplification and overexpression of FGFR1 may be a major contributor to poor prognosis in luminal-type breast cancers, driving anchorage-independent proliferation and endocrine therapy resistance. In our study we found a subset of lobular breast carcinoma, be characterized by FGFR-1 amplification or gains of chromogenic signals, not only in primary tumours but also in the metastatic tissue. In this context, patients affected by lobular breast carcinomas and characterized by gains/amplification of FGFR-1 molecule, could receive effective regimens (predictive biomarker) with FGFR-1 inhibitors (targeted therapy). Differently, lobular breast carcinomas usually show absence of Her-2/neu and topoisomerase-IIα gene amplification (according to both FDA or ASCO/CAP cut-offs), thus patients constantly lack the ad hoc predictive rationale for receiving common chemotherapy that includes anthracyclines; in addition, invasive lobular carcinomas commonly underexpress Her-2 showing lack of tailored scheme of therapies.
The efficacy of anti-FGFR-1 inhibitor is increasing also in carcinomas arising from other organs. Interestingly, Dutt et al. found gains of FGFR-1 gene in a subset of lung adenocarcinomas and squamous lung carcinomas and notably they demonstrated that a non-small cell lung carcinoma cell line harbouring focal amplification of FGFR-1 is dependent on FGFR-1 activity for cell growth, as treatment of this cell line either with FGFR1-specific shRNAs or with FGFR small molecule enzymatic inhibitors did lead to cell growth inhibition. They concluded that FGFR-1 may represent a promising therapeutic target in non-small cell lung cancer and even better in the orphan subtype of lung carcinoma such as the squamous.
Intratumoral heterogeneity can lead to underestimation of the tumor genomics portrayed from single tumoral samples and may present challenges to personalized-medicine and biomarker development. Intratumor heterogeneity may foster tumor adaptation and therapeutic failure. We found no significant heterogeneity in matched primary and metastatic lobular breast carcinomas in regard to FGFR-1 gains or amplification. The predictive biomarker may be assessed on metastatic tissue or in primary carcinomas, and the predictiveness to anti-FGFR-1 inhibitor is prone to be similar.
The assessment of the FGFR-1 gene status may be performed on formalin-fixed and paraffin embedded materials, actually by using commercially available kit. The design of new clinical trials have to take in account these clustered molecular patterns in order to make an appropriate correlation between abnormalities of the FGFR-1 gene and predictiveness of emerging drug efficacy. The clinical significance in between amplification (>6 chromogenic signals) versus simple gains (3–6 signals) may be assessed differently; we actually do not know if anti-FGFR1 inhibitors work equally. Polyploidy of nuclei due to disruption of the mitotic machinery may be the reasons of simple gains of cromogenic signals, differently to true gene amplification where additional gains of signals are more than reference probes (true gene amplification). We clustered these two molecular groups similarly to those distinct in the Her-2/neu assessment when overall gene copy number is scored.
The FGFR-1 overexpression is already been noted, however no data is available on its presence in a metastatic setting. Reis-Filho et al. studied eighteen infiltrative lobular breast carcinomas and reported gains of FGFR-1 by arrayCGH in five cases and validated specific gains of genomic material after in situ hybridization analysis. Courjal et al. studied by Southern blotting a total of 1875 breast tumor DNAs with 26 probes mapping at 15 distinct chromosomal localizations. They identified a group of carcinomas with amplifications at 11q13 and/or 8p12 and was predominantly composed of estrogen receptor-positive tumors and presented a large proportion of lobular cancers. Coamplifications of the 11q13 and 8p12 regions are common in breast carcinomas, suggesting synergy between the amplicons[19, 20]. Gelsi-Boyer et al. found genomic “turbulence” at 8p11 in a subset of lobular breast carcinomas whereas Adelaide et al. described a recurrent chromosome translocation breakpoint near the 8p12 locus. Jacquemier et al. observed that overexpression of FGFR-1 to be associated with small, well-differentiated diploid breast cancers. Elbauomy Elsheikh et al. suggested that FGFR-1 amplification may be an independent predictor of overall survival in patients affected by breast carcinoma.
The fibroblast growth factor (FGF) signaling axis is increasingly implicated in tumorigenesis and chemoresistance. Several small molecule FGF-receptor (FGFR) kinase inhibitors are currently in clinical development[5, 8, 26], however, the predominant activity of the most advanced of these agents is against the kinase insert domain receptor, which compromises the FGFR selectivity[27, 28]. Most of studies did not encounter the lobular subtypes of breast carcinoma when evaluating FGFR-1 gene status. Shiang et al. suggested that FGFR-1 amplification or protein overexpression in breast cancers may be an indicator for brivanib treatment, where it may have direct anti-proliferative effects in addition to its’ anti-angiogenic effects. Gru et al. found a twofold increase in FGFR1 amplification in invasive breast carcinoma versus pure ductal carcinoma in situ, and they observed a significant reduction of the disease-free survival in amplified versus unamplified invasive breast carcinoma. Balko et al. suggested that the addition of FGFR inhibitors to ER-targeted therapy will yield a superior antitumor effect. Jang et al. reported the increased frequency of FGFR1 amplification in invasive carcinomas compared with pure in situ ductal carcinoma. They suggested a role for FGFR1 amplification in the progression of breast cancer including in situ-to-invasive transition. Only 3.2% of their cases had lobular features, thus we can not compare our findings. Massabeau et al. observed a correlation in between patients showing response to chemotherapy and the FGFR-1 positive findings by immunophenotypical analysis at cancerous tissue level. Moelens et al. reported around 20-30% of invasive ductal breast carcinoma harboring FGFR-1 amplification (ratio >1.3). Again, no lobular have been analyses.
Overall, emerging interest is present at any level of translational research in regard to FGFR-1 as a biomarker predictive of responsiveness to targeted and/or personalized therapies. In the era of tailored therapies, patients affected by the lobular subtype of breast carcinoma with FGFR-1 amplification could be approached to the new target biological therapy such as FGFR-1 inhibitor, with promising clinical efficacy. The lobular infiltrative breast carcinoma may become an ex orphan cancer of targeted therapy. In our study, we observed the presence of FGFR-1 genomic abnormalities such as gains and amplification in a significant subset of metastatic lobular breast carcinoma, with clear implications for targeted therapy use.