This review discusses the current state of biomarker discovery for the purposes of diagnostics and therapeutic monitoring. We underscore relevant challenges that have defined the gap between biomarker discovery and meaningful clinical use. We highlight recent advancements in and propose a way to think about future biomarker development.

Invasive breast cancer is the most common malignancy in women. Its most common site of metastasis is represented by the lymph nodes of axilla, and the sentinel lymph node (SLN) is the first station of nodal metastasis. Axillary SLN biopsy accurately predicts axillary lymph node status and has been accepted as standard of care for nodal staging in breast cancer. To date, the morphologic aspects of SLN metastasis have not been considered by the oncologic staging system. Extranodal extension (ENE) of nodal metastasis, defined as extension of neoplastic cells through the nodal capsule into the peri-nodal adipose tissue, has recently emerged as an important prognostic factor in several types of malignancies. It has also been considered as a possible predictor of non-sentinel node tumor burden in SLN-positive breast cancer patients. We sought out to clarify the prognostic role of ENE in SLN-positive breast cancer patients in terms of overall and disease-free survival by conducting a systematic review and meta-analysis. Among 172 screened articles, 5 were eligible for the meta-analysis; they globally include 624 patients (163 ENE+ and 461 ENE-) with a median follow-up of 58 months. ENE was associated with a higher risk of both mortality (RR = 2.51; 95% CI: 1.66-3.79, p < 0.0001, I(2) = 0%) and recurrence of disease (RR = 2.07, 95% CI: 1.38-3.10, p < 0.0001, I(2) = 0%). These findings recommend the consideration of ENE from the gross sampling to the histopathological evaluation, in perspectives to be validated and included in the oncologic staging.

Interferon regulatory factor-1 (IRF-1) is a transcription factor that acts as a tumor suppressor and causes apoptosis in cancer cells. We evaluated IRF-1-induced apoptosis in gastric cancer cell lines. We established stable clones in AGS cells that have a tetracycline-inducible IRF-1 expression system. We used these clones and recombinant adenovirus expressing IRF-1 to explore the mechanism of IRF-1-induced apoptosis in gastric cancer. Expression of IRF-1 causes apoptosis in gastric cancer cell lines as shown by phosphatidylserine exposure and cleavage of caspase-8, caspase-3, and Bid with the mitochondrial release of cytochrome c. However, inhibition of caspase-8 and Bid did not inhibit apoptosis and did not decrease cleaved caspase-9 or mitochondrial release of cytochrome c. We then show that IRF-1 upregulates PUMA (p53 upregulated modulator of apoptosis), which is known to activate apoptosis by the intrinsic pathway; this can be p53-independent. IRF-1 binds to distinct sites in the promoter of PUMA and activates PUMA transcription. Moreover, molecular markers of mitochondrial apoptosis are eliminated in PUMA knockout and knockdown cells and phosphatidylserine exposure is decreased dramatically. Finally, we show that IFN-γ induces IRF-1-mediated upregulation of PUMA in cancer cells. We conclude that IRF-1 can induce apoptosis by the intrinsic pathway independent of the extrinsic pathway by upregulation of PUMA.