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Osteosarcoma occurs predominantly in children and young adults. High-grade tumors require multidisciplinary treatment consisting of chemotherapy in the neoadjuvant and adjuvant settings, along with surgical intervention. Despite this approach, death from respiratory failure secondary to the development and progression of pulmonary metastases remains a significant problem. Here, we identify the IL-11 receptor α subunit (IL-11Rα) as a cell surface marker of tumor progression that correlates with poor prognosis in patients with osteosarcoma. We also show that both IL-11Rα and its ligand, IL-11, are specifically up-regulated in human metastatic osteosarcoma cell lines; engagement of this autocrine loop leads to tumor cell proliferation, invasion, and anchorage-independent growth in vitro. Consistently, IL-11Rα promotes lung colonization by human metastatic osteosarcoma cells in vivo in an orthotopic mouse model. Finally, we evaluate the IL-11Rα-targeted proapoptotic agent bone metastasis-targeting peptidomimetic (BMTP-11) in preclinical models of primary intratibial osteosarcomas, observing marked inhibition of both tumor growth and lung metastases. This effect was enhanced when BMTP-11 was combined with the chemotherapeutic drug gemcitabine. Our combined data support the development of approaches targeting IL-11Rα, and establish BMTP-11 as a leading drug candidate for clinical translation in patients with high-risk osteosarcoma.

Inflammatory breast carcinoma (IBC) is one of the most lethal forms of human breast cancer, and effective treatment for IBC is an unmet clinical need in contemporary oncology. Tumor-targeted theranostic approaches are emerging in precision medicine, but only a few specific biomarkers are available. Here we report up-regulation of the 78-kDa glucose-regulated protein (GRP78) in two independent discovery and validation sets of specimens derived from IBC patients, suggesting translational promise for clinical applications. We show that a GRP78-binding motif displayed on either bacteriophage or adeno-associated virus/phage (AAVP) particles or loop-grafted onto a human antibody fragment specifically targets orthotopic IBC and other aggressive breast cancer models in vivo. To evaluate the theranostic value, we used GRP78-targeting AAVP particles to deliver the human Herpes simplex virus thymidine kinase type-1 (HSVtk) transgene, obtaining simultaneous in vivo diagnosis through PET imaging and tumor treatment by selective activation of the prodrug ganciclovir at tumor sites. Translation of this AAVP system is expected simultaneously to image, monitor, and treat the IBC phenotype and possibly other aggressive (e.g., invasive and/or metastatic) subtypes of breast cancer, based on the inducible cell-surface expression of the stress-response chaperone GRP78, and possibily other cell-surface receptors in human tumors.

Significance Prostate cancer has an unpredictable natural history: While most tumors are clinically indolent, some patients display lethal phenotypes. Serum prostate-specific antigen is the most often used test in prostate cancer but screening is controversial. Treatment options are limited for metastatic disease, hence the need for early diagnosis. Prostate cancer antigen 3 ( PCA3 ), a long noncoding RNA, is the most specific biomarker identified and approved as a diagnostic test. However, its inherent biological function (if any) has remained elusive. We uncovered a negative transdominant oncogenic role for PCA3 that down-regulates an unrecognized tumor suppressor gene, PRUNE2 (a human homolog of the Drosophila prune gene) thereby promoting malignant cell growth. This work defines a unique biological function for PCA3 in prostate cancer.

Six members of the microRNA-17 (miR-17) family were mapped to three different chromosomes, although they share the same seed sequence and are predicted to target common genes, among which are those encoding hypoxia-inducible factor-1α (HIF1A) and VEGFA. Here, we evaluated the in vivo expression profile of the miR-17 family in the murine retinopathy of prematurity (ROP) model, whereby Vegfa expression is highly enhanced at the early stage of retinal neovascularization, and we found simultaneous reduction of all miR-17 family members at this stage. Using gene reporter assays, we observed binding of these miRs to specific sites in the 3' UTRs of Hif1a and Vegfa. Furthermore, overexpression of these miRs decreased HIF1A and VEGFA expression in vitro. Our data indicate that this miR-17 family elicits a regulatory synergistic down-regulation of Hif1a and Vegfa expression in this biological model. We propose the existence of a coordinated regulatory network, in which diverse miRs are synchronously regulated to target the Hif1a transcription factor, which in turn, potentiates and reinforces the regulatory effects of the miRs on Vegfa to trigger and sustain a significant physiological response.

In response to an urgent need for improved diagnostic and predictive serum biomarkers for management of metastatic prostate cancer, we used phage display fingerprinting to analyze sequentially acquired serum samples from a patient with advancing prostate cancer. We identified a peptide ligand, CTFAGSSC, demonstrating an increased recovery frequency over time. Serum antibody reactivity to this peptide epitope increased in the index patient, in parallel with development of deteriorating symptoms. The antigen mimicking the peptide epitope was identified as alpha-2-Heremans-Schmid glycoprotein, also known as fetuin-A. Metastatic prostate cancer cell lines and bone metastasis samples displayed robust fetuin-A expression, and we demonstrated serum immune reactivity to fetuin-A with concomitant development of metastatic castrate-resistant disease in a large cohort of prostate cancer patients. Whereas fetuin-A is an established tumor antigen in several types of cancer, including breast cancer, glioblastoma, and pancreas cancer, this report is to our knowledge the first study implicating fetuin-A in prostate cancer and indicating that autoantibodies specific for fetuin-A show utility as a prognostic indicator for prostate cancer patients prone to progress to metastatic disease.

Inhibition of blood vessel formation is a viable therapeutic approach in angiogenesis-dependent diseases. We previously used a combinatorial screening on vascular endothelial growth factor (VEGF)-activated endothelial cells to select the sequence CPQPRPLC and showed that the motif Arg-Pro-Leu targets VEGF receptor-1 and neuropilin-1. Here, we evaluated and validated D (LPR), a derivative molecule with strong antiangiogenesis attributes. This prototype drug markedly inhibits neovascularization in three mouse models: Matrigel-based assay, functional human/murine blood vessel formation, and retinopathy of prematurity. In addition to its systemic activity, D (LPR) also inhibits retinal angiogenesis when administered in an eye-drop formulation. Finally, in preliminary studies, we have showed targeted drug activity in an experimental tumor-bearing mouse model. These results show that drugs targeting extracellular domains of VEGF receptors are active, affect signal transduction, and have potential for clinical application. On a larger context, this study illustrates the power of ligand-directed selection plus retro-inversion for rapid drug discovery and development.

The epidermal growth factor receptor (EGFR), a tyrosine kinase, is central to human tumorigenesis. Typically, three classes of drugs inhibit tyrosine kinase pathways: blocking antibodies, small kinase inhibitors, and soluble ligand receptor traps/decoys. Only the first two types of EGFR-binding inhibitory drugs are clinically available; notably, no EGFR decoy has yet been developed. Here we identify small molecules mimicking EGFR and that functionally behave as soluble decoys for EGF and TGFα, ligands that would otherwise activate downstream signaling. After combinatorial library selection on EGFR ligands, a panel of binding peptides was narrowed by structure–function analysis. The most active motif was CVRAC (EGFR 283–287), which is necessary and sufficient for specific EGFR ligand binding. Finally, a synthetic retro-inverted derivative, D (CARVC), became our preclinical prototype of choice. This study reveals an EGFR-decoy drug candidate with translational potential.

Mammalian cell membranes provide an interface between the intracellular and extracellular compartments. It is currently thought that cytoplasmic signaling adapter proteins play no functional role within the extracellular tumor environment. Here, by selecting combinatorial random peptide libraries in tumor-bearing mice, we uncovered a direct, specific, and functional interaction between CRKL, an adapter protein [with Src homology 2 (SH2)- and SH3-containing domains], and the plexin-semaphorin-integrin domain of β 1 integrin in the extracellular milieu. Through assays in vitro, in cellulo, and in vivo, we show that this unconventional and as yet unrecognized protein–protein interaction between a regulatory integrin domain (rather than a ligand-binding one) and an intracellular adapter (acting outside of the cells) triggers an alternative integrin-mediated cascade for cell growth and survival. Based on these data, here we propose that a secreted form of the SH3/SH2 adaptor protein CRKL may act as a growth-promoting factor driving tumorigenesis and may lead to the development of cancer therapeutics targeting secreted CRKL.