New and potential clinical applications of KRAS as a cancer biomarker

GLI1-targeting drugs induce replication stress and homologous recombination deficiency and synergize with PARP-targeted therapies in triple negative breast cancer cells

Triple negative breast cancer (TNBC), an aggressive and highly metastatic subtype of breast cancer. Glioma-associated oncogene 1 (GLI1) is a transcription factor and effector of the Hedgehog (Hh) signaling pathway, and is predictive of poor survival for TNBC patients. A nanostring DNA Damage Response (DDR) mRNA panel was used to identify GLI1-induced regulation of DDR genes. Western blots, immunohistochemistry and immunofluorescence were used to evaluate protein expression. Colony assays and mammosphere formation assays were utilized to assess survival of cancer cells. Flow cytometry analyses were employed to evaluate changes in the cell cycle profile, and DNA fiber assays were used to analyze alterations in replication dynamics in TNBC cells. The UALCAN portal and Ensemble programs were used for computational analysis of TCGA data. CompuSyn software was used to calculate combination index (CI) values to assess synergism in drug combination experiments. Inhibition of GLI1 in TNBC cells transcriptionally downregulate expression of FANCD2 and its foci formation, and causes a homologous recombination repair (HR) deficiency. As HR-deficient cancer cells are sensitive to PARP-targeted therapies, we evaluated a combination of the GLI1 inhibitor, GANT61, and a PARP inhibitor (olaparib) in TNBC cells. Combination of GANT61 and olaparib elevated DNA damage levels and these drug combinations caused synergistic lethality to TNBC cells. Aberrantly activated GLI1 regulates HR-mediated DNA repair by transcriptionally regulating FANCD2 to overcome chemotherapy-induced replication stress and DNA damage, and it contributes to resistance of TNBC cells to therapeutics.

GUCY2C as a biomarker to target precision therapies for patients with colorectal cancer

Introduction

Colorectal cancer (CRC) is one of the most-deadly malignancies worldwide. Current therapeutic regimens for CRC patients are relatively generic, based primarily on disease type and stage, with little variation. As the field of molecular oncology advances, so too must therapeutic management of CRC. Understanding molecular heterogeneity has led to a new-found promotion for precision therapy in CRC; underlining the diversity of molecularly targeted therapies based on individual tumor characteristics.

Areas covered

We review current approaches for the treatment of CRC and discuss the potential of precision therapy in advanced CRC. We highlight the utility of the intestinal protein guanylyl cyclase C (GUCY2C), as a multi-purpose biomarker and unique therapeutic target in CRC. Here, we summarize current GUCY2C-targeted approaches for treatment of CRC.

Expert opinion

The GUCY2C biomarker has multi-faceted utility in medicine. Developmental investment of GUCY2C as a diagnostic and therapeutic biomarker offers a variety of options taking the molecular characteristics of cancer into account. From GUCY2C-targeted therapies, namely cancer vaccines, CAR-T cells, and monoclonal antibodies, to GUCY2C agonists for chemoprevention in those who are at high risk for developing colorectal cancer, the utility of this protein provides many avenues for exploration with significance in the field of precision medicine.

Aberrant GLI1 Activation in DNA Damage Response, Carcinogenesis and Chemoresistance

The canonical hedgehog (HH) pathway is a multicomponent signaling cascade (HH, protein patched homolog 1 (PTCH1), smoothened (SMO)) that plays a pivotal role during embryonic development through activation of downstream effector molecules, namely glioma-associated oncogene homolog 1 (GLI1), GLI2 and GLI3. Activation of GLIs must be tightly regulated as they modulate target genes which control tissue patterning, stem cell maintenance, and differentiation during development. However, dysregulation or mutations in HH signaling leads to genomic instability (GI) and various cancers, for example, germline mutation in PTCH1 lead to Gorlin syndrome, a condition where patients develop numerous basal cell carcinomas and rarely rhabdomyosarcoma (RMS). Activating mutations in SMO have also been recognized in sporadic cases of medulloblastoma and SMO is overexpressed in many other cancers. Recently, studies in several human cancers have shown that GLI1 expression is independent from HH ligand and canonical intracellular signaling through PTCH and SMO. In fact, this aberrantly regulated GLI1 has been linked to several non-canonical oncogenic growth signals such as Kirsten rat sarcoma viral oncogene homolog (KRAS), avian myelocytomatosis virus oncogene cellular homolog (C-MYC), transforming growth factor β (TGFβ), wingless-type MMTV integration site family (WNT) and β-catenin. Recent studies from our lab and other independent studies demonstrate that aberrantly expressed GLI1 influences the integrity of several DNA damage response and repair signals, and if altered, these networks can contribute to GI and impact tumor response to chemo- and radiation therapies. Furthermore, the ineffectiveness of SMO inhibitors in clinical studies argues for the development of GLI1-specific inhibitors in order to develop effective therapeutic modalities to treat these tumors. In this review, we focus on summarizing current understanding of the molecular, biochemical and cellular basis for aberrant GLI1 expression and discuss GLI1-mediated HH signaling on DNA damage responses, carcinogenesis and chemoresistance.

Pancreatic cancer biomarkers and their implication in cancer diagnosis and epidemiology

Pancreatic cancer is the fourth most common cause of cancer-related mortality in the United States. Biomarkers are needed to detect this cancer early during the disease development and for screening populations to identify those who are at risk. In cancer, “biomarker” refers to a substance or process that is indicative of the presence of cancer in the body. A biomarker might be either a molecule secreted by a tumor or it can be a specific response of the body to the presence of cancer. Genetic, epigenetic, proteomic, glycomic, and imaging biomarkers can be used for cancer diagnosis, prognosis, and epidemiology. A number of potential biomarkers have been identified for pancreatic cancer. These markers can be assayed in non-invasively collected biofluids. These biomarkers need analytical and clinical validation so that they can be used for the purpose of screening and diagnosing pancreatic cancer and determining disease prognosis. In this article, the latest developments in pancreatic cancer biomarkers are discussed.