Unravelling of the comparative Transcriptomic Profile of Gallbladder Cancer using mRNA sequencing

A Comprehensive narrative review of transcriptomics and epigenomics of gallbladder cancer

ABSTRACTS

Gallbladder cancer (GBC) is one of the quiet prevalent and aggressive biliary tract malignant neoplasms distinguished by significant cellular heterogeneity, metastatic activity, and a poor prognosis, with varied frequency worldwide. Most cases are detected incidentally while routine screening imaging or pathological investigation of cholecystectomy tissues and usually present with advanced disease. The surgical resection is usually done in the initial clinical stage having limited spread. Despite the surgical therapy, the death rate is significant. Furthermore, the molecular mechanisms affecting the clinical course of inflammatory gallbladder to carcinogenesis remain poorly understood. There is an impending need for developing diagnostic biomarkers and targeted approaches for GBC. The newer molecular platform, such as next-generation sequencing (NGS), such as RNA-sequencing (RNAseq), single-cell sequencing, and microarray technology, has revolutionized the field of genomics, opened a new perspective in defining genetic and epigenetic characteristics identifying molecules as possible therapeutic targets. Therefore, in this review, we would analyze transcriptomic and epigenomics profiles of GBC using already published high-throughput sequencing-based studies published between 2010 and 2023. The review would also analyze the possible impact of the technological advancement on the patient management strategy and overall survival. This may also help identify target genes and pathways linked to GBC, which may help establish molecular biomarkers, for early GBC diagnosis, personalized therapy, and management.

Prognostic value of functional SMAD4 localization in extrahepatic bile duct cancer

Background

SMAD4 is a key mediator of TGFβ signaling and one of the mutated genes in extrahepatic bile duct cancer (eBDC). It has been also reported that SMAD4 has dual functions, in carcinogenesis via silencing and in tumor invasion/metastasis via signaling, depending on tumor stage. We previously visualized more nuclear transitioning functional SMAD4 at the tumor invasion front than the central lesion. So, we investigated the localization of functional SMAD4 (e.g., invasion area or metastasis lesion) and its association with chemotherapy and chemo-radiation therapy.

Methods

We performed SMAD4 immunostaining on 98 resected eBDC specimens and evaluated the presence of the functional form of nuclear SMAD4 at the central lesion, invasion front, and metastatic lymph node. We also examined the influence on chemotherapy after recurrence (n = 33) and neoadjuvant chemo-radiation therapy (NAC-RT, n = 21) and the prognostic value of using retrospective data.

Results

In 73 patients without NAC-RT, 8.2% had loss of SMAD4 expression and 23.3% had heterogeneous expression. Patients without SMAD4 expression at any site had significantly poorer overall survival (OS) than other patients (P = 0.014). Expression of SMAD4 at the invasion front was related to better survival (recurrence-free survival [RFS] P = 0.033; OS P = 0.047), and no SMAD4 expression at the metastatic lymph node was related to poorer OS (P = 0.011). The patients who had high SMAD4 expression had poorer prognosis after recurrence (RFS P = 0.011; OS P = 0.056). At the residual cancer in the resected specimen, SMAD4 was highly expressed after NAC-RT (P = 0.039).

Conclusions

Loss of SMAD4 protein expression was a poor prognostic factor in eBDC at resectable stage. However, the intensity of functional SMAD4 in eBDC is a marker of resistance to chemo-radiotherapy and malignant potential at advanced stages.