Molecular alterations and targeted therapy in pancreatic ductal adenocarcinoma

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is a malignancy characterized by a poor prognosis and high mortality rate. Genetic mutations and altered molecular pathways serve as targets in precise therapy. Using next-generation sequencing (NGS), these aberrant alterations can be identified and used to develop strategies that will selectively kill cancerous cells in patients with PDAC. The realization of targeted therapies in patients with PDAC may be summarized by three approaches. First, because oncogenes play a pivotal role in tumorigenesis, inhibition of dysregulated oncogenes is a promising method (Table 3). Numerous researchers are developing strategies to target oncogenes, such as KRAS, NRG1, and NTRK and related molecules, although most of the results are unsatisfactory. Accordingly, emerging strategies are being developed to target these oncogenes, including simultaneously inhibiting multiple molecules or pathways, modification of mutant residues by small molecules, and RNA interference. Second, researchers have attempted to reactivate inactivated tumour suppressors or modulate related molecules. TP53, CDKN2A and SMAD4 are three major tumour suppressors involved in PDAC. Advances have been achieved in clinical and preclinical trials of therapies targeting these three genes, and further investigations are warranted. The TGF-β-SMAD4 signalling pathway plays a dual role in PDAC tumorigenesis and participates in mediating tumour-stroma crosstalk and modulating the tumour microenvironment (TME); thus, molecular subtyping of pancreatic cancer according to the SMAD4 mutation status may be a promising precision oncology technique. Finally, genes such as KDM6A and BRCA have vital roles in maintaining the structural stability and physiological functions of normal chromosomes and are deficient in some patients with PDAC, thus serving as potential targets for correcting these deficiencies and precisely killing these aberrant tumour cells. Recent clinical trials, such as the POLO (Pancreas Cancer Olaparib Ongoing) trial, have reported encouraging outcomes. In addition to genetic event-guided treatment, immunotherapies such as chimeric antigen receptor T cells (CAR-T), antibody-drug conjugates, and immune checkpoint inhibitors also exhibit the potential to target tumours precisely, although the clinical value of immunotherapies as treatments for PDAC is still limited. In this review, we focus on recent preclinical and clinical advances in therapies targeting aberrant genes and pathways and predict the future trend of precision oncology for PDAC.

Keywords: Epigenetics; Immunotherapy; Oncogenes; Pancreatic ductal adenocarcinoma; Precision oncology; Synthetic lethality; Therapeutic targets; Tumour suppressors.

Fig 1

ERBB family comprises four receptor tyrosine kinases including the epidermal growth factor receptor (EGFR). Activation of EGFR recruits RAS guanine nucleotide exchange factors (GEFs) such as son-of-sevenless (SOS). GEFs and GTPase activating proteins (GAPs) switch RAS between the GTP-bound and GDP-bound states. The constitutive GDP-bound state activates multiple downstream molecules in PDAC. Gene fusions such as NRG1 fusions can also initiate PDAC via ectopic ERBB receptor signalling pathway. IGF-1R has crosstalk with EGFR and produces tumour resistance to EGFR inhibitors. Various inhibitors could inhibit RAS signalling pathway molecules by targeting corresponding molecules such as EGFR, MEK, PI3K

Fig 2

Various factors could cause DNA single-strand breaks (SSBs). SSBs are repaired by poly (ADP-ribose) polymerase (PARP) through the base excision repair (BER) mechanism. Therefore, the application of PARP inhibitors will enable BER and cause many SSBs. These lesions will transfer to DNA double-strand breaks (DSBs) during cell proliferation. DSBs are repaired by BRCA through the gene conversion (GC) pathway in normal cells. However, in BRCA-loss cancer cells, DSBs cannot be repaired and will lead to fatal genomic instability