The therapeutic potential value of Cancer-testis antigens in immunotherapy of gastric cancer

Gastric cancer (GC) is the fourth most common cause of mortality and the fifth for incidence, globally. Diagnosis, early prognosis, and therapy remains challenging for this condition, and new tumor-associated antigens are required for its detection and immunotherapy. Cancer-testis antigens (CTAs) are a subfamily of tumor-associated antigens (TAAs) that have been identified as potential biomarkers and targets for cancer immunotherapy. The CTAs-restricted expression pattern in tumor cells and their potential immunogenicity identify them as attractive target candidates in CTA-based diagnosis or prognosis or immunotherapy. To date, numerous studies have reported the dysregulation of CTAs in GC. Several clinical trials have been done to assess CTA-based immunotherapeutic potential in the treatment of GC patients. NY-ESO-1, MAGE, and KK-LC-1 have been used in GC clinical trials. We review recent studies that have investigated the potential of the CTAs in GC regarding the expression, function, aggressive phenotype, prognosis, and immunological responses as well as their possible clinical significance as immunotherapeutic targets with a focus on challenges and future interventions.

TWIST1 Plays Role in Expression of Stemness State Markers in ESCC

BACKGROUND

Stemness markers play critical roles in the maintenance of key properties of embryonic stem cells (ESCs), including the pluripotency, stemness state, and self-renewal capacities, as well as cell fate decision. Some of these features are present in cancer stem cells (CSCs). TWIST1, as a bHLH transcription factor oncogene, is involved in the epithelial-mesenchymal transition (EMT) process in both embryonic and cancer development. Our aim in this study was to investigate the functional correlation between TWIST1 and the involved genes in the process of CSCs self-renewal in human esophageal squamous cell carcinoma (ESCC) line KYSE-30.

METHODS

TWIST1 overexpression was enforced in the ESCC KYSE-30 cells using retroviral vector containing the specific pruf-IRES-GFP-hTWIST1 sequence. Following RNA extraction and cDNA synthesis, the mRNA expression profile of TWIST1 and the stem cell markers, including BMI1, CRIPTO1, DPPA2, KLF4, SOX2, NANOG, and MSI1, were assessed using relative comparative real-time PCR.

RESULTS

Ectopic expression of TWIST1 in KYSE-30 cells resulted in an increased expression of TWIST1 compared to control GFP cells by nearly 9-fold. Transduction of TWIST1-retroviral particles caused a significant enhancement in BMI1, CRIPTO1, DPPA2, KLF4, and SOX2 mRNA expression, approximately 4.5-, 3.2-, 5.5-, 3.5-, and 3.7-folds, respectively, whereas this increased TWIST1 expression caused no change in the mRNA expression of NANOG and MSI1 genes.

CONCLUSIONS

TWIST1 gene ectopic expression in KYSE-30 cells enhanced the level of cancer stem cell markers' mRNA expression. These results may emphasize the role of TWIST1 in the self-renewal process and may corroborate the involvement of TWIST1 in the stemness state capacity of ESCC cell line KYSE-30, as well as its potential as a therapeutic target.

Transcription Factor CTCFL Promotes Cell Proliferation, Migration, and Invasion in Gastric Cancer via Activating DPPA2

Objective

To explore the relationship between CTCFL and DPPA2 and validate the positive role of CTCFL/DPPA2 in cell malignant behaviors in gastric cancer.

Methods

We predicted gastric cancer-related transcription factors and corresponding target mRNAs through bioinformatics. Levels of CTCFL and DPPA2 were assessed via qRT-PCR and western blot. In vitro experiments were utilized to assay the cell biological behaviors. CHIP was utilized for the assessment of the targeted relationship between CTCFL and DPPA2.

Results

CTCFL and DPPA2 were both highly expressed in gastric cancer cells, and high CTCFLL and DPPA2 could promote cell malignant behaviors. CHIP validated that DPPA2 was a target of CTCFL. In addition, high DPPA2 rescued the repressive impact of CTCFL silencing on the cell proliferation, migration, and invasion in gastric cancer.

Conclusion

The transcription factor CTCFL fosters cell proliferative, migratory, and invasive properties via activating DPPA2 in gastric cancer.

Keeping your options open: insights from Dppa2/4 into how epigenetic priming factors promote cell plasticity

The concept of cellular plasticity is particularly apt in early embryonic development, where there is a tug-of-war between the stability and flexibility of cell identity. This balance is controlled in part through epigenetic mechanisms. Epigenetic plasticity dictates how malleable cells are to change by adjusting the potential to initiate new transcriptional programmes. The higher the plasticity of a cell, the more readily it can adapt and change its identity in response to external stimuli such as differentiation cues. Epigenetic plasticity is regulated in part through the action of epigenetic priming factors which establish this permissive epigenetic landscape at genomic regulatory elements to enable future transcriptional changes. Recent studies on the DNA binding proteins Developmental Pluripotency Associated 2 and 4 (Dppa2/4) support their roles as epigenetic priming factors in facilitating cell fate transitions. Here, using Dppa2/4 as a case study, the concept of epigenetic plasticity and molecular mechanism of epigenetic priming factors will be explored. Understanding how epigenetic priming factors function is key not only to improve our understanding of the tight control of development, but also to give insights into how this goes awry in diseases of cell identity, such as cancer.

SPOP suppresses testicular germ cell tumors progression through ubiquitination and degradation of DPPA2

Dysregulation of the ubiquitin-proteasome pathway is strongly associated with cancer initiation and progression. Speckle-type POZ(pox virus and zinc finger protein) protein(SPOP) is an adapter protein of CUL3-based E3 ubiquitin ligase complexes. Gene expression profiling from the Cancer Genome Atlas (TCGA) suggests that SPOP is downregulated in testicular germ cell tumors (TGCTs), but the specific contribution of this protein remains to be explored. In this study, we show that the germ line-specific factor DPPA2 was identified as a proteolytic substrate for the SPOP-CUL3-RBX1 E3 ubiquitin-ligase complex. SPOP specifically binds to a SPOP-binding consensus (SBC) degron located in DPPA2 and targets DPPA2 for degradation via the ubiquitin-proteasome pathway. SPOP downregulation increases the expression of pluripotency markers OCT4 and Nanog but decreases that of early differentiation marker gene Fst. This effect is partly dependent on its activity toward DPPA2. In addition, the dysregulation of SPOP-DPPA2 axis contributes to the malignant transformation phenotypes of TGCT cells.

Dppa2/4 Facilitate Epigenetic Remodeling during Reprogramming to Pluripotency

As somatic cells are converted into induced pluripotent stem cells (iPSCs), their chromatin is remodeled to a pluripotent configuration with unique euchromatin-to-heterochromatin ratios, DNA methylation patterns, and enhancer and promoter status. The molecular machinery underlying this process is largely unknown. Here, we show that embryonic stem cell (ESC)-specific factors Dppa2 and Dppa4 play a key role in resetting the epigenome to a pluripotent state. They are induced in reprogramming intermediates, function as a heterodimer, and are required for efficient reprogramming of mouse and human cells. When co-expressed with Oct4, Klf4, Sox2, and Myc (OKSM) factors, Dppa2/4 yield reprogramming efficiencies that exceed 80% and accelerate reprogramming kinetics, generating iPSCs in 2 to 4 days. When bound to chromatin, Dppa2/4 initiate global chromatin decompaction via the DNA damage response pathway and contribute to downregulation of somatic genes and activation of ESC enhancers, all of which enables an efficient transition to pluripotency. Our work provides critical insights into how the epigenome is remodeled during acquisition of pluripotency.