Cetuximab induces eme1-mediated DNA repair: a novel mechanism for cetuximab resistance

MicroRNA-449a Inhibits Triple Negative Breast Cancer by Disturbing DNA Repair and Chromatid Separation

Chromosomal instability (CIN) can be a driver of tumorigenesis but is also a promising therapeutic target for cancer associated with poor prognosis such as triple negative breast cancer (TNBC). The treatment of TNBC cells with defects in DNA repair genes with poly(ADP-ribose) polymerase inhibitor (PARPi) massively increases CIN, resulting in apoptosis. Here, we identified a previously unknown role of microRNA-449a in CIN. The transfection of TNBC cell lines HCC38, HCC1937 and HCC1395 with microRNA-449a mimics led to induced apoptosis, reduced cell proliferation, and reduced expression of genes in homology directed repair (HDR) in microarray analyses. EME1 was identified as a new target gene by immunoprecipitation and luciferase assays. The reduced expression of EME1 led to an increased frequency of ultrafine bridges, 53BP1 foci, and micronuclei. The induced expression of microRNA-449a elevated CIN beyond tolerable levels and induced apoptosis in TNBC cell lines by two different mechanisms: (I) promoting chromatid mis-segregation by targeting endonuclease EME1 and (II) inhibiting HDR by downregulating key players of the HDR network such as E2F3, BIRC5, BRCA2 and RAD51. The ectopic expression of microRNA-449a enhanced the toxic effect of PARPi in cells with pathogenic germline BRCA1 variants. The newly identified role makes microRNA-449a an interesting therapeutic target for TNBC.

Essential meiotic structure-specific endonuclease1 (EME1) promotes malignant features in gastric cancer cells via the Akt/GSK3B/CCND1 pathway

DNA damage plays a key role in various biological processes involved in malignant disease, the role of the DNA damage repair gene EME1 (essential meiotic structure-specific endonuclease 1) in gastric cancer (GC) development is unknown. This work aimed to investigate expression and role of EME1 in tumorigenesis. Quantitative real-time polymerase chain reaction (qRT-PCR), immunoblot, cell viability and dual-luciferase reporter assays, RNAi and gene transfection, and immunofluorescent staining were performed to assess EME1 regulation in GC tumorigenesis. Further, mouse xenografts were established for in vivo mechanistic studies. EME1 was found to be upregulated in both gastric cancer cells and clinically obtained tumors. Additionally, EME1 levels were strongly associated with the differentiation level of GC and lymph node metastasis. In vivo and in vitro knockdown of EME1 markedly suppressed the proliferative, migratory, and invasive abilities of GC cells and enhanced apoptotic cell death and cell cycle arrest rates. Mechanistically, EME1 modulated Akt/GSK3B/CCND1 signaling. MYB may also have contributed to EME1-dependent gastric carcinogenesis. Elevated EME1 expressions may enhance the proliferative and metastatic abilities of GC cells, thereby acting as a tumor-promoting factor via Akt. These findings reveal that EME1 is an important biomarker for GC prognosis and treatment in humans.

Abbreviations: Essential meiotic structure-specific endonuclease 1 (EME1); MYB proto-oncogene (MYB); Cell counting kit-8 (CCK-8); 4,6-diamimo-2-phenyl indole (DAPI); Quantitative real-time PCR (qRT-PCR); Gastric cancer (GC); Immunofluorescence (IF); Small interfering RNA (siRNA); Small hairpin RNA (shRNA); Alpha serine threonine-protein kinase (Akt); Glycogen synthase kinase 3 beta (GSK3B); Cyclin D1 (CCND1); Glyceraldehyde-3-phosphate dehydrogenase (GAPDH); Disease-free survival (DFS); Overall survival (OS); Negative controls (NC); American Joint Committee on Cancer (AJCC); Coding sequence (CDS); Lymph node metastasis (LNM); Tris-Buffered Saline-Tween-20 (TBST); Horseradish Peroxidase (HRP); Electrochemiluminescence (ECL); Polyvinylidene Fluoride (PVDF); Excision repair cross complementation group 1 (ERCC1).

Cytokines, JAK-STAT Signaling and Radiation-Induced DNA Repair in Solid Tumors: Novel Opportunities for Radiation Therapy

A number of solid tumors are treated with radiation therapy (RT) as a curative modality. At the same time, for certain types of cancers the applicable doses of RT are not high enough to result in a successful eradication of cancer cells. This is often caused by limited pharmacological tools and strategies to selectively sensitize tumors to RT while simultaneously sparing normal tissues from RT. We present an outline of a novel strategy for RT sensitization of solid tumors utilizing Jak inhibitors. Here, recently published pre-clinical data are reviewed which demonstrate the promising role of Jak inhibition in sensitization of tumors to RT. A wide number of currently approved Jak inhibitors for non-malignant conditions are summarized including Jak inhibitors currently in clinical development. Finally, intersection between Jak/Stat and the levels of serum cytokines are presented and discussed as they relate to susceptibility to RT.

The Latest Battles Between EGFR Monoclonal Antibodies and Resistant Tumor Cells

Epidermal growth factor receptor (EGFR) is a tyrosine kinase receptor involved in homeostatic regulation of normal cells and carcinogenesis of epithelial malignancies. With rapid development of the precision medicine era, a series of new therapies targeting EGFR are underway. Four EGFR monoclonal antibody drugs (cetuximab, panitumumab, nimotuzumab, and necitumumab) are already on the market, and a dozen other EGFR monoclonal antibodies are in clinical trials. Here, we comprehensively review the newly identified biological properties and anti-tumor mechanisms of EGFR monoclonal antibodies. We summarize recently completed and ongoing clinical trials of the classic and new EGFR monoclonal antibodies. More importantly, according to our new standard, we re-classify the complex evolving tumor cell resistance mechanisms, including those involving exosomes, non-coding RNA and the tumor microenvironment, against EGFR monoclonal antibodies. Finally, we analyzed the limitations of EGFR monoclonal antibody therapy, and discussed the current strategies overcoming EGFR related drug resistance. This review will help us better understand the latest battles between EGFR monoclonal antibodies and resistant tumor cells, and the future directions to develop anti-tumor EGFR monoclonal antibodies with durable effects.

STAT3 Contributes to Radioresistance in Cancer

Radiotherapy has been used in the clinic for more than one century and it is recognized as one of the main methods in the treatment of malignant tumors. Signal Transducers and Activators of Transcription 3 (STAT3) is reported to be upregulated in many tumor types, and it is believed to be involved in the tumorigenesis, development and malignant behaviors of tumors. Previous studies also found that STAT3 contributes to chemo-resistance of various tumor types. Recently, many studies reported that STAT3 is involved in the response of tumor cells to radiotherapy. But until now, the role of the STAT3 in radioresistance has not been systematically demonstrated. In this study, we will review the radioresistance induced by STAT3 and relative solutions will be discussed.

Breaking the selectivity-uptake trade-off of photoimmunoconjugates with nanoliposomal irinotecan for synergistic multi-tier cancer targeting

BACKGROUND

Photoimmunotherapy involves targeted delivery of photosensitizers via an antibody conjugate (i.e., photoimmunoconjugate, PIC) followed by light activation for selective tumor killing. The trade-off between PIC selectivity and PIC uptake is a major drawback limiting the efficacy of photoimmunotherapy. Despite ample evidence showing that photoimmunotherapy is most effective when combined with chemotherapy, the design of nanocarriers to co-deliver PICs and chemotherapy drugs remains an unmet need. To overcome these challenges, we developed a novel photoimmunoconjugate-nanoliposome (PIC-Nal) comprising of three clinically used agents: anti-epidermal growth factor receptor (anti-EGFR) monoclonal antibody cetuximab (Cet), benzoporphyrin derivative (BPD) photosensitizer, and irinotecan (IRI) chemotherapy.

RESULTS

The BPD photosensitizers were first tethered to Cet at a molar ratio of 6:1 using carbodiimide chemistry to form PICs. Conjugation of PICs onto nanoliposome irinotecan (Nal-IRI) was facilitated by copper-free click chemistry, which resulted in monodispersed PIC-Nal-IRI with an average size of 158.8 ± 15.6 nm. PIC-Nal-IRI is highly selective against EGFR-overexpressing epithelial ovarian cancer cells with 2- to 6-fold less accumulation in low EGFR expressing cells. Successful coupling of PIC onto Nal-IRI enhanced PIC uptake and photoimmunotherapy efficacy by up to 30% in OVCAR-5 cells. Furthermore, PIC-Nal-IRI synergistically reduced cancer viability via a unique three-way mechanism (i.e., EGFR downregulation, mitochondrial depolarization, and DNA damage).

CONCLUSION

It is increasingly evident that the most effective therapies for cancer will involve combination treatments that target multiple non-overlapping pathways while minimizing side effects. Nanotechnology combined with photochemistry provides a unique opportunity to simultaneously deliver and activate multiple drugs that target all major regions of a cancer cell-plasma membrane, cytoplasm, and nucleus. PIC-Nal-IRI offers a promising strategy to overcome the selectivity-uptake trade-off, improve photoimmunotherapy efficacy, and enable multi-tier cancer targeting. Controllable drug compartmentalization, easy surface modification, and high clinical relevance collectively make PIC-Nal-IRI extremely valuable and merits further investigations in living animals.

Cytotoxicity of ultraviolet-C radiation on a heterogeneous population of human glioblastoma multiforme cells: Meta-analysis

INTRODUCTION

Current treatment strategies for glioblastoma multiforme are limited due to early recurrence and heterogeneity of the cell population that causes a varied response to treatment. Ultraviolet-C (UVC) radiation may be a potential adjuvant treatment that could theoretically be delivered locally by implantable micro-electromechanical systems that sense and kill early recurrence and/or minimally residual cancer. in vitro irradiation experiments are limited because they commonly use a single cell line. Therefore other methods are required to investigate cytotoxicity across a heterogeneous population of GBM.

METHODS

A meta-analysis was conducted to assess the cytotoxic effects of UVC radiation on human GBM cell lines, with or without genetic modification, in monolayer to simulate a heterogeneous model. 16 publications were included using 14 different cell lines and 19 gene vectors. Effect sizes were calculated for cell survival, viability, apoptosis and proliferation. Univariate meta-regression was used to investigate the effects of radiant exposure (J/m²) and timing on cytotoxicity.

RESULTS

UVC resulted in a 70.9% (CI: 63.6%-78.2%) reduction in survival, 16.6% (CI: 10.8%-22.4%) increase in apoptosis, 32.0% (CI: 9.95%-54.2%) reduction in viability, and 413.8% (CI: 95.7%-731.9%) reduction in proliferation of GBM cell lines compared to controls. Radiant exposure was significantly associated with survival (R² = 0.486, p < 0.0001) but not with apoptosis or viability.

CONCLUSIONS

This study provides more data on the therapeutic translational potential of UVC to a more clinically-realistic context. Overall, UVC is cytotoxic to GBM cell lines in aggregate and may be clinically useful when combined with genetic modification or other adjuvant treatments.

Effects of Ultraviolet Radiation on Glioma: Systematic Review

Glioblastoma multiforme is the most aggressive primary brain tumor. Treatment is largely palliative, with current strategies unable to prevent inevitable tumor recurrence. Implantable micro-electromechanical systems are becoming more feasible for the management of several human diseases. These systems may have a role in detecting tumor recurrence and delivering localized therapies. One potential therapeutic tool is ultraviolet (UV) light. This systematic review assesses the effects of UV light on glioma cells. A total of 47 publications are included. The large majority were in vitro experiments conducted on human glioblastoma cell lines in monolayer. In these cells, UV light was shown to induce apoptosis and the expression of genes or activation of proteins that modulate cell death, repair, and proliferation. The nature and magnitude of cellular response varied by UV wavelength, dose, cell line, and time after irradiation. UVC (wavelength 100-280 nm) was most effective at inducing apoptosis, and this effect was dose dependent. The included studies had varied methodologies, complicating reconciliation of results. Further work will be required to determine the best regime of UV irradiation for therapeutic use. J. Cell. Biochem. 118: 4063-4071, 2017. © 2017 Wiley Periodicals, Inc.

Challenges to targeting epidermal growth factor receptor in glioblastoma: escape mechanisms and combinatorial treatment strategies

Epidermal growth factor receptor (EGFR) gene amplification and activating mutations are common findings in glioblastomas. EGFR is at the top of a downstream signaling cascade that regulates important characteristics of glioblastoma cells, including cellular proliferation, migration, and survival. Targeting EGFR has therefore been regarded as a promising therapeutic strategy in glioblastoma for decades. However, although various pharmacological inhibitors and anti-EGFR antibodies are available, the antiglioma activity of these agents has been largely limited to preclinical models, whereas their administration to glioblastoma patients was characterized by lack of clinical benefit. Comprehensive efforts have been made within the last years to understand the underlying mechanisms that confer resistance to EGFR inhibition in glioma cells. The absence of well-known mutations that predict response to EGFR tyrosine kinase inhibitors (TKIs) in gliomas as well as the presence of redundant and alternative compensatory pathways are among the most important escape mechanisms that prevent potent antiglioma effects of EGFR-targeting drugs. Accordingly, an increasing number of in vitro and in vivo studies are aimed at overcoming this resistance by combinatorial approaches using anti-EGFR treatment together with one or more additional drugs. Novel insights into the molecular mechanisms mediating resistance to anti-EGFR treatment and promising combinatorial approaches may help to better define a future role for EGFR inhibition in the treatment of glioblastoma.