Targeting GPNMB with glembatumumab vedotin: Current developments and future opportunities for the treatment of cancer

Targeting stem cells in the realm of drug-resistant breast cancer

Since its first documentation, breast cancer (BC) has been a conundrum that ails millions of women every year. This cancer has been well studied by researchers all over the world, which has improved the patient outcome significantly. There are many diagnostic markers to identify the disease, but early detection and then subclassification of this cancer remain dubious. Even after the correct diagnosis, more than half the patients come back with a more aggressive and metastatic tumor. The underpinning mechanism that governs the resistance includes over-amplification of receptors, mutations in key gene targets, and activation of different signaling. A plethora of drugs have been devised that have shown promising results in clinical settings. However, in recent times, the role played by cancer stem cells in disease progression and their interaction in mediating the resistance to cellular insults have come into the limelight. As breast cancer stem cells (BCSCs) are dormant in nature, it is highly likely that they fail to directly respond to the cytotoxic drugs which are meant for ablating rapidly proliferating cells. Furthermore, the absence of well-characterized, drug-able surface markers to date, has limited the application of targeted therapies in complete eradication of the disease. In this review, our intent is to discuss versatile therapeutics in practice followed by discussing the upcoming therapy strategies in the pipeline for BC. Furthermore, we focus on the roles played by BCSCs in mediating the resistance, and therefore, the aspects of new therapeutics against BCSCs under development that may ease the burden in future has also been discussed.

Towards frailty biomarkers: Candidates from genes and pathways regulated in aging and age-related diseases

OBJECTIVE

Use of the frailty index to measure an accumulation of deficits has been proven a valuable method for identifying elderly people at risk for increased vulnerability, disease, injury, and mortality. However, complementary molecular frailty biomarkers or ideally biomarker panels have not yet been identified. We conducted a systematic search to identify biomarker candidates for a frailty biomarker panel.

METHODS

Gene expression databases were searched (http://genomics.senescence.info/genes including GenAge, AnAge, LongevityMap, CellAge, DrugAge, Digital Aging Atlas) to identify genes regulated in aging, longevity, and age-related diseases with a focus on secreted factors or molecules detectable in body fluids as potential frailty biomarkers. Factors broadly expressed, related to several "hallmark of aging" pathways as well as used or predicted as biomarkers in other disease settings, particularly age-related pathologies, were identified. This set of biomarkers was further expanded according to the expertise and experience of the authors. In the next step, biomarkers were assigned to six "hallmark of aging" pathways, namely (1) inflammation, (2) mitochondria and apoptosis, (3) calcium homeostasis, (4) fibrosis, (5) NMJ (neuromuscular junction) and neurons, (6) cytoskeleton and hormones, or (7) other principles and an extensive literature search was performed for each candidate to explore their potential and priority as frailty biomarkers.

RESULTS

A total of 44 markers were evaluated in the seven categories listed above, and 19 were awarded a high priority score, 22 identified as medium priority and three were low priority. In each category high and medium priority markers were identified.

CONCLUSION

Biomarker panels for frailty would be of high value and better than single markers. Based on our search we would propose a core panel of frailty biomarkers consisting of (1) CXCL10 (C-X-C motif chemokine ligand 10), IL-6 (interleukin 6), CX3CL1 (C-X3-C motif chemokine ligand 1), (2) GDF15 (growth differentiation factor 15), FNDC5 (fibronectin type III domain containing 5), vimentin (VIM), (3) regucalcin (RGN/SMP30), calreticulin, (4) PLAU (plasminogen activator, urokinase), AGT (angiotensinogen), (5) BDNF (brain derived neurotrophic factor), progranulin (PGRN), (6) α-klotho (KL), FGF23 (fibroblast growth factor 23), FGF21, leptin (LEP), (7) miRNA (micro Ribonucleic acid) panel (to be further defined), AHCY (adenosylhomocysteinase) and KRT18 (keratin 18). An expanded panel would also include (1) pentraxin (PTX3), sVCAM/ICAM (soluble vascular cell adhesion molecule 1/Intercellular adhesion molecule 1), defensin α, (2) APP (amyloid beta precursor protein), LDH (lactate dehydrogenase), (3) S100B (S100 calcium binding protein B), (4) TGFβ (transforming growth factor beta), PAI-1 (plasminogen activator inhibitor 1), TGM2 (transglutaminase 2), (5) sRAGE (soluble receptor for advanced glycosylation end products), HMGB1 (high mobility group box 1), C3/C1Q (complement factor 3/1Q), ST2 (Interleukin 1 receptor like 1), agrin (AGRN), (6) IGF-1 (insulin-like growth factor 1), resistin (RETN), adiponectin (ADIPOQ), ghrelin (GHRL), growth hormone (GH), (7) microparticle panel (to be further defined), GpnmB (glycoprotein nonmetastatic melanoma protein B) and lactoferrin (LTF). We believe that these predicted panels need to be experimentally explored in animal models and frail cohorts in order to ascertain their diagnostic, prognostic and therapeutic potential.

Glycoprotein nmb Is Exposed on the Surface of Dormant Breast Cancer Cells and Induces Stem Cell-like Properties

Glycoprotein nmb (GPNMB) is a type I transmembrane protein that contributes to the initiation and malignant progression of breast cancer through induction of epithelial-mesenchymal transition (EMT). Although it is known that EMT is associated with not only cancer invasion but also acquisition of cancer stem cell (CSC) properties, the function of GPNMB in this acquisition of CSC properties has yet to be elucidated. To address this issue, we utilized a three-dimensional (3D) sphere culture method to examine the correlation between GPNMB and CSC properties in breast cancer cells. Three-dimensional sphere cultures induced higher expression of CSC genes and EMT-inducing transcription factor (EMT-TF) genes than the 2D monolayer cultures. Three-dimensional culture also induced cell surface expression of GPNMB on limited numbers of cells in the spheres, whereas the 2D cultures did not. Therefore, we isolated cell surface-GPNMB^high and -GPNMB^low cells from the spheres. Cell surface-GPNMB^high cells expressed high levels of CSC genes and EMT-TF genes, had significantly higher sphere-forming frequencies than the cell surface-GPNMB^low cells, and showed no detectable levels of proliferation marker genes. Similar results were obtained from transplanted breast tumors. Furthermore, wild-type GPNMB, but not mutant GPNMB (YF), which lacks tumorigenic activity, induced CSC-like properties in breast epithelial cells. These findings suggest that GPNMB is exposed on the surface of dormant breast cancer cells and its activity contributes to the acquisition of stem cell-like properties.Significance: These findings suggest that cell surface expression of GPNMB could serve as a marker and promising therapeutic target of breast cancer cells with stem cell-like properties. Cancer Res; 78(22); 6424-35. ©2018 AACR.

Recent Advances in the Treatment of Breast Cancer

Breast cancer (BC) is the most common malignancy in women. It is classified into a few major molecular subtypes according to hormone and growth factor receptor expression. Over the past few years, substantial advances have been made in the discovery of new drugs for treating BC. Improved understanding of the biologic heterogeneity of BC has allowed the development of more effective and individualized approach to treatment. In this review, we provide an update about the current treatment strategy and discuss the various emerging novel therapies for the major molecular subtypes of BC. A brief account of the clinical development of inhibitors of poly(ADP-ribose) polymerase, cyclin-dependent kinases 4 and 6, phosphatidylinositol 3-kinase/protein kinase B/mammalian target of rapamycin pathway, histone deacetylation, multi-targeting tyrosine kinases, and immune checkpoints for personalized treatment of BC is included. However, no targeted drug has been approved for the most aggressive subtype-triple negative breast cancer (TNBC). Thus, we discuss the heterogeneity of TNBC and how molecular subtyping of TNBC may help drug discovery for this deadly disease. The emergence of drug resistance also poses threat to the successful development of targeted therapy in various molecular subtypes of BC. New clinical trials should incorporate advanced methods to identify changes induced by drug treatment, which may be associated with the upregulation of compensatory signaling pathways in drug resistant cancer cells.

Direct molecular dissection of tumor parenchyma from tumor stroma in tumor xenograft using mass spectrometry-based glycoproteomics

The most widely used cancer animal model is the human-murine tumor xenograft. Unbiased molecular dissection of tumor parenchyma versus stroma in human-murine xenografts is critical for elucidating dysregulated protein networks/pathways and developing therapeutics that may target these two functionally codependent compartments. Although antibody-reliant technologies (e.g., immunohistochemistry, imaging mass cytometry) are capable of distinguishing tumor-proper versus stromal proteins, the breadth or extent of targets is limited. Here, we report an antibody-free targeted cross-species glycoproteomic (TCSG) approach that enables direct dissection of human tumor parenchyma from murine tumor stroma at the molecular/protein level in tumor xenografts at a selectivity rate presently unattainable by other means. This approach was used to segment/dissect and obtain the protein complement phenotype of the tumor stroma and parenchyma of the metastatic human lung adenocarcinoma A549 xenograft, with no need for tissue microdissection prior to mass-spectrometry analysis. An extensive molecular map of the tumor proper and the associated microenvironment was generated along with the top functional N-glycosylated protein networks enriched in each compartment. Importantly, immunohistochemistry-based cross-validation of selected parenchymal and stromal targets applied on human tissue samples of lung adenocarcinoma and normal adjacent tissue is indicative of a noteworthy translational capacity for this unique approach that may facilitate identifications of novel targets for next generation antibody therapies and development of real time preclinical tumor models.

Glycoprotein Non-Metastatic Melanoma Protein B (GPNMB) and Cancer: A Novel Potential Therapeutic Target

Glycoprotein non-metastatic melanoma protein B (GPNMB) is a transmembrane protein enriched on the cell surface of cancer cells, including melanoma, glioblastoma, and triple-negative breast cancer. There is growing evidence identifying GPNMB as a tumor-promoter; however, despite its biological and clinical significance, the molecular mechanisms engaged by GPNMB to promote tumorigenesis are not well understood. GPNMB promotes aggressive behaviors such as tumor cell proliferation, migration, and invasion. The extracellular domain of GPNMB shed from the cell surface interacts with integrins to facilitate in the recruitment of immune-suppressive and pro-angiogenic cells to the tumor microenvironment, thereby enhancing tumor migration and invasion. GPNMB also modulates receptor tyrosine kinases and integrin signaling in a cell autonomous fashion, leading to downstream kinase signaling that in turn triggers the expression and secretion of tumorigenic factors such as matrix metalloproteinases (MMPs) and cytokines. Therefore, GPNMB exerts its pro-tumorigenic role both intracellularly and in a paracrine fashion through shedding its extracellular domain. This review highlights the importance of GPNMB in cancer progression and discusses molecular mediators of GPNMB-induced tumor growth and invasion.

Data-Driven prioritisation of antibody-drug conjugate targets in head and neck squamous cell carcinoma

BACKGROUND

For patients with recurrent or metastatic head and neck squamous cell carcinoma (HNSCC) palliative treatment options that improve overall survival are limited. The prognosis in this group remains poor and there is an unmet need for new therapeutic options. An emerging class of therapeutics, targeting tumor-specific antigens, are antibodies bound to a cytotoxic agent, known as antibody-drug conjugates (ADCs). The aim of this study was to prioritize ADC targets in HNSCC.

METHODS

With a systematic search, we identified 55 different ADC targets currently targeted by registered ADCs and ADCs under clinical evaluation. For these 55 ADC targets, protein overexpression was predicted in a dataset containing 344 HNSCC mRNA expression profiles by using a method called functional genomic mRNA profiling. The ADC target with the highest predicted overexpression was validated by performing immunohistochemistry (IHC) on an independent tissue microarray containing 414 HNSCC tumors.

RESULTS

The predicted top 5 overexpressed ADC targets in HNSCC were: glycoprotein nmb (GPNMB), SLIT and NTRK-like family member 6, epidermal growth factor receptor, CD74 and CD44. IHC validation showed combined cytoplasmic and membranous GPNMB protein expression in 92.0% of the cases. Strong expression was seen in 65.9% of the cases. In addition, 86.5% and 67.7% of cases showed ≥5% and >25% GPNMB positive tumor cells, respectively.

CONCLUSIONS

This study provides a data-driven prioritization of ADCs targets that will facilitate clinicians and drug developers in deciding which ADC should be taken for further clinical evaluation in HNSCC. This might help to improve disease outcome of HNSCC patients.

Recent advances in brain tumor therapy: application of electrospun nanofibers

Despite much effort to treat glioblastoma multiforme (GBM), the median survival of patients has not significantly improved. The high rate of tumor recurrence after tumor resection and the blood-brain barrier (BBB) decrease the treatment efficacy. Local drug delivery at the surgical resection site via implantable electrospun nanofibers not only circumvents the BBB, but can also reduce the rate of tumor recurrence. Nanofibers can provide a sustained release and a high concentration of chemotherapeutics at the tumor vicinity, while decreasing their systemic exposure and toxicity. In another scenario, aligned nanofibers can mimic the topographical features of the brain extracellular matrix (ECM), which can be utilized for in vitro studies on GBM cell migration. This strategy is beneficial to investigate the interactions of tumor cells with the microenvironment which has a dominant role in regulating tumor formation, progression, and metastasis.

Cancer immunotherapy beyond immune checkpoint inhibitors

Malignant cells have the capacity to rapidly grow exponentially and spread in part by suppressing, evading, and exploiting the host immune system. Immunotherapy is a form of oncologic treatment directed towards enhancing the host immune system against cancer. In recent years, manipulation of immune checkpoints or pathways has emerged as an important and effective form of immunotherapy. Agents that target cytotoxic T lymphocyte-associated molecule-4 (CTLA-4), programmed cell death receptor-1 (PD-1), and programmed cell death ligand-1 (PD-L1) are the most widely studied and recognized. Immunotherapy, however, extends beyond immune checkpoint therapy by using new molecules such as chimeric monoclonal antibodies and antibody drug conjugates that target malignant cells and promote their destruction. Genetically modified T cells expressing chimeric antigen receptors are able to recognize specific antigens on cancer cells and subsequently activate the immune system. Native or genetically modified viruses with oncolytic activity are of great interest as, besides destroying malignant cells, they can increase anti-tumor activity in response to the release of new antigens and danger signals as a result of infection and tumor cell lysis. Vaccines are also being explored, either in the form of autologous or allogenic tumor peptide antigens, genetically modified dendritic cells that express tumor peptides, or even in the use of RNA, DNA, bacteria, or virus as vectors of specific tumor markers. Most of these agents are yet under development, but they promise to be important options to boost the host immune system to control and eliminate malignancy. In this review, we have provided detailed discussion of different forms of immunotherapy agents other than checkpoint-modifying drugs. The specific focus of this manuscript is to include first-in-human phase I and phase I/II clinical trials intended to allow the identification of those drugs that most likely will continue to develop and possibly join the immunotherapeutic arsenal in a near future.