FOXA1 protein could be a diagnostic marker for aggressive prostate cancer

Researchers at The University of Texas MD Anderson Cancer Center have identified FOXA1 as a potentially sensitive marker for small cell carcinoma of the prostate, a difficult-to-diagnose aggressive cancer subtype

The ‘Forkhead box protein A1’ (FOXA1) protein may help to identify aggressive prostate cancers that are difficult to diagnose after they lose conventional prostatic markers, according to researchers at The University of Texas MD Anderson Cancer Center, Houston, USA.

The study suggests that FOXA1 could serve as a highly sensitive diagnostic marker for small cell carcinoma of the prostate and possibly for other aggressive prostate cancer subtypes. The work was led by Dr Jianping Zhao, assistant professor of anatomic pathology at the Anderson Cancer Center.

Aggressive prostate cancers can present a serious diagnostic challenge, particularly after treatment. Standard treatment for prostate cancer often includes androgen deprivation therapy which aims to suppress the androgen signalling that drives many prostate tumours. However, some aggressive cancers develop resistance through androgen-independent pathways. These treatment-resistant tumours are associated with poorer outcomes and may lose expression of the markers that pathologists usually use to confirm a prostatic origin.

Small cell carcinoma of the prostate is one such aggressive subtype. It can be especially difficult to diagnose because it often loses standard prostate markers, including NKX3.1, a protein commonly used to support a diagnosis of prostate origin. When these markers are absent, it can be difficult to determine whether a metastatic tumour represents progression from a known prostate cancer or whether it is a separate primary tumour that arose at another anatomical site. That uncertainty can complicate both prognosis and treatment selection.

“The detectable expression of FOXA1 in most small cell carcinomas of the prostate makes it a potentially viable option for diagnosing aggressive subtypes that lose conventional markers,” Zhao said.

“While further study is needed to understand the specific molecular mechanisms, we are encouraged by these results, which could help pathologists make prognostic and therapeutic decisions to improve patient care,” he added.

To search for a novel marker, the researchers used The Cancer Genome Atlas database to assess candidate proteins that might remain detectable in aggressive prostate cancers. FOXA1, emerged as a promising candidate. The team then examined FOXA1 expression in tissue samples from primary and metastatic prostate tumours, as well as samples from other cancer types.

The analysis found FOXA1 expression in 80 per cent of primary small cell carcinoma of the prostate cases and 57 per cent of metastatic cases. Its expression was notably higher in prostate cancer and reached levels similar to those seen with NKX3.1. Importantly, FOXA1 remained detectable in a substantial proportion of tumours that commonly lose NKX3.1 expression, which suggests that it could complement existing diagnostic panels rather than replace them.

The findings have indicated that FOXA1 could be particularly valuable in difficult diagnostic cases, where conventional immunohistochemical markers fail to provide a clear answer. For pathologists, an additional sensitive marker could help to establish tumour origin more confidently, especially in metastatic disease or in cancers altered by prior therapy.

The researchers cautioned that further evaluation will be needed before FOXA1 can be adopted widely as a clinical biomarker. Future studies will need to assess its expression across other aggressive prostate cancer subtypes and clarify the molecular mechanisms that underpin its persistence in tumours that lose other prostatic markers. Prospective clinical studies also will be required to validate its diagnostic performance in routine pathology practice.