Neuropilins (NRPs) are non-tyrosine kinase cell surface glycoproteins expressed in all vertebrates and widely conserved across species. The two isoforms, such as neuropilin-1 (NRP1) and neuropilin-2 (NRP2), mainly act as coreceptors for class III Semaphorins and for members of the vascular endothelial growth factor family of molecules and are widely known for their role in a wide array of physiological processes, such as cardiovascular, neuronal development and patterning, angiogenesis, lymphangiogenesis, as well as various clinical disorders. Intriguingly, additional roles for NRPs occur with myeloid and lymphoid cells, in normal physiological as well as different pathological conditions, including cancer, immunological disorders, and bone diseases. However, little is known concerning the molecular pathways that govern these functions. In addition, NRP1 expression has been characterized in different immune cellular phenotypes including macrophages, dendritic cells, and T cell subsets, especially regulatory T cell populations. By contrast, the functions of NRP2 in immune cells are less well known. In this review, we briefly summarize the genomic organization, structure, and binding partners of the NRPs and extensively discuss the recent advances in their role and function in different immune cell subsets and their clinical implications.

Despite recent advancement in medicine, nearly 50% of patients with colorectal cancer show recurrence of the disease. Although the reasons for the high relapse are not fully understood, the presence of chemo- and radiotherapy-resistant cancer stem/stem-like cells, where many oncomirs like microRNA-21 (miR-21) are upregulated, could be one of the underlying causes. miR-21 regulates the processes of invasion and metastasis by downregulating multiple tumor/metastatic suppressor genes including PTEN (phosphatase and tensin homolog). Tumor suppressor protein PTEN controls self-renewal of stem cells. Indeed, our current data demonstrate a marked downregulation of PTEN in SCID mice xenografts of miR-21 over-expressing colon cancer HCT116 cells. Colonospheres that are highly enriched in cancer stem/stem like cells reveal increased miR-21 expression and decreased PTEN. Difluorinated curcumin (CDF), a novel analog of the dietary ingredient curcumin, which has been shown to inhibit the growth of 5-Flurouracil + Oxaliplatin resistant colon cancer cells, downregulated miR-21 in chemo-resistant colon cancer HCT116 and HT-29 cells and restored PTEN levels with subsequent reduction in Akt phosphorylation. Similar results were also observed in metastatic colon cancer SW620 cells. Since PTEN-Akt confers drug resistance to different malignancies including colorectal cancer, our observation of normalization of miR-21-PTEN-Akt pathway by CDF suggests that the compound could be a potential therapeutic agent for chemotherapy-resistant colorectal cancer.

BackgroundColorectal Cancer (CRC) is one of the leading causes of death worldwide. Numerous cellular events, including deregulated expression of microRNAs (miRNAs), specifically the family of miR-34 consisting of miR-34a, b and c, is known to regulate the processes of growth and metastasis.MethodsWe evaluated the expression of miR-34 in formalin-fixed paraffin-embedded (FFPE) human colon cancer tissue specimens compared to normal colonic mucosa. Moreover, we also assessed the expression of miR-34 in colon cancer cell lines treated with our newly developed synthetic analogue of curcumin referred as difluorinated curcumin (CDF) compared to well known inhibitor of methyl transferase.ResultsWe found that the expression of miR-34a and miR-34c was down-regulated in colon cancer specimens compared to normal colonic mucosa and the loss of expression was also consistent with data from colon cancer cell lines. This down-regulation was attributed to promoter hypermethylation, because we found that the treatment of colon cancer cells with 5-aza-2´-deoxycytidine, a methyltransferase inhibitor, markedly induced the levels of miR-34a and miR-34c expression. Likewise, CDF was very effective in the re-expression of miR-34a and miR-34c, which was consistent with inhibition of cell growth of both chemo-sensitive and chemo-resistant colon cancer cells. The re-expression of miR-34 led to a marked reduction in the expression of its target gene, Notch-1.ConclusionThe loss of expression of miR-34 in colon cancer is in part due to promoter hypermethylation of miR-34, which can be re-expressed with our novel agent CDF, suggesting that CDF could be a novel demethylating agent for restoring the expression of miR-34 family, and thus CDF could become a newer therapeutic agent for the treatment of colon cancer.

The tumor microenvironment plays a critical role in regulating breast tumor progression. Signaling between preadipocytes and breast cancer cells has been found to promote breast tumor formation and metastasis. Exosomes secreted from preadipocytes are important components of the cancer stem cell niche. Mouse preadipocytes (3T3L1) are treated with the natural antitumor compound shikonin (SK) and exosomes derived from mouse preadipocytes are co-cultured with MCF10DCIS cells. We examine how preadipocyte-derived exosomes can regulate early-stage breast cancer via regulating stem cell renewal, cell migration, and tumor formation. We identify a critical miR-140/SOX2/SOX9 axis that regulates differentiation, stemness, and migration in the tumor microenvironment. Next, we find that the natural antitumor compound SK can inhibit preadipocyte signaling inhibiting nearby ductal carcinoma in situ (DCIS) cells. Through co-culture experiments, we find that SK-treated preadipocytes secrete exosomes with high levels of miR-140, which can impact nearby DCIS cells through targeting SOX9 signaling. Finally, we find that preadipocyte-derived exosomes promote tumorigenesis in vivo, providing strong support for the importance of exosomal signaling in the tumor microenvironment. Our data also show that targeting the tumor microenvironment may assist in blocking tumor progression.

Tumor-associated macrophages (TAM) are causally associated with tumorigenesis as well as regulation of antitumor immune responses and have emerged as potential immunotherapeutic targets. Recent evidence suggests TAM phagocytose apoptotic tumor cells within the tumor microenvironment through efferocytosis in an immunologically silent manner, thus maintaining an immunosuppressed microenvironment. The signal transduction pathways coupling efferocytosis and immunosuppression are not well known. Neuropilin-2 (NRP2) is a member of the membrane-associated neuropilin family and has been reported in different immune cells but is poorly characterized. In this study, we show that NRP2 is expressed during macrophage differentiation, is induced by tumor cells, and regulates phagocytosis in macrophages. Furthermore, NRP2 in TAM promoted efferocytosis and facilitated tumor growth. Deletion of NRP2 from TAM impaired the clearance of apoptotic tumor cells and increased secondary necrosis within tumors. This resulted in a break in the immune tolerance and reinitiated antitumor immune responses, characterized by robust infiltration of CD8 T and natural killer cells. This result suggests NRP2 may act as a molecular mediator that connects efferocytosis and immune suppression. Deletion of NRP2 in TAM downregulated several immunosuppressive and tumor-promoting genes and upregulated immunostimulatory genes in the myeloid compartment. Taken together, our study demonstrates that TAM-derived NRP2 plays a crucial role in tumor promotion through efferocytosis, opening the enticing option for the development of effective immunotherapy targeting TAM. Neuropilin-2 in macrophages promotes tumor growth by regulating efferocytosis of apoptotic tumor cells and orchestrating immune suppression. http://cancerres.aacrjournals.org/content/canres/78/19/5600/F1.large.jpg .

Whereas FSH action is critical for the growth of preantral follicles, its role in the development of primordial follicles is controversial. The objective of the present study was to evaluate whether perinatal (fetal through early postnatal) FSH action is needed for the formation of primordial follicles, which first appear in the hamster ovary on the 7th to 8th day of postnatal life. A single dose of FSH-specific polyclonal antibody was injected into pregnant hamsters on the 12th, 13th, or 14th day of gestation and into newborn hamsters. Some of the antibody-exposed postnatal hamsters were injected with a single dose of equine CG (eCG) to check the reversibility of the antibody action. Ovaries were collected on D8pn or D12pn, and the percentage of primordial, primary, and secondary follicles was quantitated morphometrically. Ovaries of 8-day-old hamsters that were born to mothers treated with a single s.c. dose of the anti-FSH-antibody on day 12 of gestation had significantly reduced numbers of primordial follicles, compared with those treated with preimmune serum or saline (2.4% vs. 25%); however, the antibody inhibition was nearly completely reversed (approximately 18%) by a single injection of eCG on the first day of life. Delaying antibody treatment during late gestation caused a time-dependent block in granulosa cell differentiation, with a consequent proportional increase in the percentage of primordial follicles. This indicates that FSH-induction of primordial follicle development begins at a critical time of ovarian development. On the other hand, shortening the postnatal duration of eCG exposure reduced the degree of reversal, suggesting that prolonged perinatal FSH action is essential for developing the full gamut of primordial follicles. These results provide the first direct evidence that FSH action during fetal ovarian development is critical for the onset of primordial follicle formation.

Colorectal cancer is the fourth most common form of cancer worldwide and ranks third among the cancer-related deaths in the US and other Western countries. It occurs with equal frequency in men and women, constituting 10% of new cancer cases in men and 11% in women. Despite recent advancement in therapeutics, the survival rates from metastatic are less than 5%. Growing evidence supports the contention that epithelial cancers including colorectal cancer, the incidence of which increases with aging, are diseases driven by the pluripotent, self-renewing cancer stem cells (CSCs). Dysregulation of Wnt, Notch, Hedgehog and/or TGF-β signaling pathways that are involved in proliferation and maintenance of CSCs leads to the development of CRC. This review focuses on the signaling pathways relevant for CRC to understand the mechanisms leading to tumor progression and therapy resistance, which may help in the development of therapeutic strategies for CRC.

Programmed cell death ligand 1 (PD-L1) is part of an immune checkpoint system that is essential for preventing autoimmunity and cancer. Recent approaches in immunotherapy that target immune checkpoints have shown great promise in a variety of cancers, including metastatic melanoma. The use of targeted molecular imaging would help identify patients who will best respond to anti-PD-L1 treatment while potentially providing key information to limit immune-related adverse effects. Recently, we developed an antibody-based PD-L1-targeted SPECT agent-In-diethylenetriaminepentaacetic acid (DTPA)-anti-PD-L1-to identify PD-L1-positive tumors in vivo. To best use such PD-L1-targeted imaging agents, it is important, as a first step, to understand how the signal is affected by different parameters. We evaluated the impact of protein concentration on the distribution ofIn-DTPA-anti-PD-L1 in a murine model of aggressive melanoma. In-DTPA-anti-PD-L1 (dissociation constant, 0.6 ± 0.1 nM) demonstrated increased uptake in B16F10 tumors at protein concentrations equaling or exceeding 1 mg/kg at 24 h and 3 mg/kg at 72 h. At 24 h, the PD-L1-rich spleen and lungs demonstrated decreasing uptake with increasing protein concentration. At 72 h, uptake in the thymus was significantly increased at protein concentrations of 3 mg/kg or greater. Both time points demonstrated increased tracer amounts remaining in circulation as the amount of cold antibody was increased. These studies demonstrate that In-DTPA-anti-PD-L1 is capable of identifying tumors that overexpresses PD-L1 and monitoring the impact of PD-L1-rich organs on the distribution of anti-PD-L1 antibodies.