We and others recently identified the gene metadherin (MTDH) as a functional driver in multiple aspects of cancer progression. It is overexpressed in cancer cells originating from a variety of tissues, partially due to DNA amplification of the chromosomal 8q22 region where this gene resides. The rapidly accumulated data from MTDH studies of the past several years have documented its role in tumorigenesis, angiogenesis, cell proliferation, survival, anchorage‐independent growth, metastasis and chemoresistance. In particular, it simultaneously helps the primary tumor cells to survive conventional chemotherapy and spread to distant organs, both of which are major contributors to cancer therapy failure and ultimately patient death. The efforts to elucidate the molecular mechanism of MTDH functions led to observations indicating its involvement in several prominent cancer‐related signaling pathways including Ras, c‐Myc, PI3K/AKT, NF‐κB, Wnt/β‐catenin, and more recently, microRNA machinery. Herein we will briefly summarize the studies that establish MTDH as a promising target for cancer therapeutics.

Although the role of miR-200s in regulating E-cadherin expression and epithelial-to-mesenchymal transition is well established, their influence on metastatic colonization remains controversial. Here we have used clinical and experimental models of breast cancer metastasis to discover a pro-metastatic role of miR-200s that goes beyond their regulation of E-cadherin and epithelial phenotype. Overexpression of miR-200s is associated with increased risk of metastasis in breast cancer and promotes metastatic colonization in mouse models, phenotypes that cannot be recapitulated by E-cadherin expression alone. Genomic and proteomic analyses revealed global shifts in gene expression upon miR-200 overexpression toward that of highly metastatic cells. miR-200s promote metastatic colonization partly through direct targeting of Sec23a, which mediates secretion of metastasis-suppressive proteins, including Igfbp4 and Tinagl1, as validated by functional and clinical correlation studies. Overall, these findings suggest a pleiotropic role of miR-200s in promoting metastatic colonization by influencing E-cadherin–dependent epithelial traits and Sec23a-mediated tumor cell secretome.

The utilization of upconverting nanophosphors (UCNP) for photodynamic therapy (PDT) has gained significant interests due to its ability to convert deep‐penetrating near‐infra red (NIR) light (i.e., 978 nm) to visible light. Previous attempts to co‐localize UCNPs with photosensitizers suffer from low photo­sensitizer loading and problems with nanoparticle aggregation. Here, the preparation of a novel composite nanoparticle formulation comprising 100 nm β−NaYF4:Yb3+,Er3+ UCNPs, and meso‐tetraphenyl porphine (TPP) photo­sensitizer, stabilized by biocompatible poly(ethylene glycol‐block‐(dl)lactic acid) block copolymers (PEG‐b‐PLA) is presented. A photosensitizer loading of 10 wt% with respect to UCNP crystal was achieved via the Flash NanoPrecipitation (FNP) process. A sterically stabilizing PEG layer on the composite nanoparticle surface prevents nanoparticle aggregation and ensures nanoparticle stability in water, PBS buffer, and culture medium containing serum proteins, resulting in nanoparticle suitable for in vivo applications. Based on in vitro studies utilizing HeLa cervical cancer cell lines, the composite nanoparticles are shown to exhibit low dark toxicity and efficient cancer cell‐killing activity upon NIR excitation. Exposure with 134 W cm−2 of 978 nm light for 45 min resulted in 75% HeLa cell death. This is the first quantification of the cell‐killing capabilities of the UCNP/TPP composite nanoparticles formulated for photodynamic therapy.

Tumor hypoxia is known to activate angiogenesis, anaerobic glycolysis, invasion, and metastasis. However, a comparative analysis of the potentially distinct functions of hypoxia in primary tumor growth and organ-specific metastasis has not been reported. Here, we show distinct hypoxia kinetics in tumors generated by the MDA-MB-231 breast cancer sublines with characteristically different primary tumor growth rates and organotropic metastasis potentials. Hypoxia-induced angiogenesis promotes both primary tumor growth and lung metastasis but is nonessential for bone metastasis. Microarray profiling revealed that hypoxia enhances the expression of a significant number of genes in the lung metastasis signature, but only activates a few bone metastasis genes, among which DUSP1 was functionally validated in this study. Despite the different mechanisms by which hypoxia promotes organ-specific metastasis, inhibition of HIF-1α with a dominant-negative form of HIF-1α or 2-methoxyestradiol reduced metastasis to both lung and bone. Consistent with the extensive functional overlap of hypoxia in promoting primary tumor growth and lung metastasis, a 45-gene hypoxia response signature efficiently stratifies breast cancer patients with low or high risks of lung metastasis, but not for bone metastasis. Our study shows distinct functions of hypoxia in regulating angiogenesis and metastasis in different organ microenvironments and establishes HIF-1α as a promising target for controlling organotropic metastasis of breast cancer.

Cancer is the result of the progressive acquisition of multiple malignant traits through the accumulation of genetic or epigenetic alterations. Recent studies have established a functional role of MTDH (Metadherin)/AEG-1 (Astrocyte Elevated Gene 1) in several crucial aspects of tumor progression, including transformation, evasion of apoptosis, invasion, metastasis, and chemoresistance. Overexpression of MTDH/AEG-1 is frequently observed in melanoma, glioma, neuroblastoma, and carcinomas of breast, prostate, liver, and esophagus and is correlated with poor clinical outcomes. MTDH/AEG-1 functions as a downstream mediator of the transforming activity of oncogenic Ha-Ras and c-Myc. Furthermore, MTDH/AEG-1 overexpression activates the PI3K/Akt, nuclear factor κB (NFκB), and Wnt/β-catenin signaling pathways to stimulate proliferation, invasion, cell survival, and chemoresistance. The lung-homing domain of MTDH/AEG-1 also mediates the adhesion of tumor cells to the vasculature of distant organs and promotes metastasis. These findings suggest that therapeutic targeting of MTDH/AEG-1 may simultaneously suppress tumor growth, block metastasis, and enhance the efficacy of chemotherapeutic treatments.