Pre-clinical assessment of A-674563 as an anti-melanoma agent

CXCL10 and CCL21 Promote Migration of Pancreatic Cancer Cells Toward Sensory Neurons and Neural Remodeling in Tumors in Mice, Associated With Pain in Patients

BACKGROUND & AIMS

Pancreatic ductal adenocarcinoma (PDAC) is frequently accompanied by excruciating pain, which has been associated with attraction of cancer cells and their invasion of intrapancreatic sensory nerves. Neutralization of the chemokine CCL2 reduced cancer-associated pain in a clinical trial, but there have been no systematic analyses of the highly diverse chemokine families and their receptors in PDAC.

METHODS

We performed an open, unbiased RNA-interference screen of mammalian chemokines in co-cultures of mouse PDAC cells (K8484) and mouse peripheral sensory neurons, and confirmed findings in studies of DT8082 PDAC cells. We studied the effects of chemokines on migration of PDAC cell lines. Orthotopic tumors were grown from K8484 cells in mice, and mice were given injections of neutralizing antibodies against chemokines, antagonists, or control antibodies. We analyzed abdominal mechanical hypersensitivity and collected tumors and analyzed them by histology and immunohistochemistry to assess neural remodeling. We collected PDAC samples and information on pain levels from 74 patients undergoing resection and measured levels of CXCR3 and CCR7 by immunohistochemistry and immunoblotting.

RESULTS

Knockdown of 9 chemokines in DRG neurons significantly reduced migration of PDAC cells towards sensory neurons. Sensory neuron-derived CCL21 and CXCL10 promoted migration of PDAC cells via their receptors CCR7 and CXCR3, respectively, which were expressed by cells in orthotopic tumors and PDAC specimens from patients. Neutralization of CCL21 or CXCL10, or their receptors, in mice with orthotopic tumors significantly reduced nociceptive hypersensitivity and nerve fiber hypertrophy and improved behavioral parameters without affecting tumor infiltration by T cells or neutrophils. Increased levels of CXCR3 and CCR7 in human PDAC specimens were associated with increased frequency of cancer-associated pain, determined from patient questionnaires.

CONCLUSIONS

In an unbiased screen of chemokines, we identified CCL21 and CXCL10 as proteins that promote migration of pancreatic cancer cells toward sensory neurons. Inhibition of these chemokines or their receptors reduce hypersensitivity in mice with orthotopic tumors, and patients with PDACs with high levels of the chemokine receptors of CXCR3 and CCR7 had increased frequency of cancer-associated pain.

Long-Time Instead of Short-Time Exposure in Vitro and Administration in Vivo of Ochratoxin A Is Consistent in Immunosuppression

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium, contaminating in a wide variety of foods and feeds. Mycotoxins, including OTA, could cause immunosuppression in almost all previous studies in vivo. However, the vast majority of results in vitro showed that mycotoxins caused immunostimulation. Why the results of studies in vitro are contrary to studies in vivo is unknown. Our study aims to explore the underlying reason and mechanism of the paradoxical effect. In this study, porcine alveolar macrophage cell line 3D4/21 was chosen as an in vitro model and treated with 1.0 μg/mL OTA for different times. Some indexes, such as expression of inflammatory cytokines, migration, phagocytosis, macrophage polarization, autophagy-related proteins, and Akt1 phosphorylation, were detected. The results showed that pro-inflammatory cytokine expression, migration, and phagocytosis were increased, with macrophage polarization to the M1 phenotype at 24 h of OTA exposure. Surprisedly, anti-inflammatory cytokine expression was increased, cell phagocytosis and migration were decreased, and macrophage polarization was switched from M1 to M2 at 72 h of OTA exposure. Furthermore, we found that long-time exposure of OTA also suppressed autophagy, and the autophagy activator blocked the OTA-induced immunosuppression. Phosphorylation of Akt1 plays a positive role in autophagy inhibition. In conclusion, long-time instead of short-time exposure of OTA in vitro induced immunosuppression. The immunosuppression mechanism of OTA in vitro involved inhibition of autophagy through upregulating p-Akt1. Our results provide new insight into research on the mechanism of mycotoxin-induced immunosuppression in vitro.

GDC-0084 inhibits cutaneous squamous cell carcinoma cell growth

GDC-0084 is a novel and potent small-molecule PI3K-mTOR dual inhibitor. The present study examined its potential activity in cutaneous squamous cell carcinoma (cSCC) cells. Our results show that GDC-0084 treatment at nanomole concentrations potently inhibited survival and proliferation of established (A431, SCC-13 and SCL-1 lines) and primary human cSCC cells. GDC-0084 induced apoptosis activation and cell cycle arrest in the cSCC cells. It was more efficient than other known PI3K-Akt-mTOR inhibitors in killing cSCC cells, but was non-cytotoxic to the normal human skin fibroblasts/keratinocytes. In A431 cells and primary cSCC cells, GDC-0084 blocked phosphorylation of key PI3K-Akt-mTOR components, including p85, Akt, S6K1 and S6. GDC-0084 also inhibited DNA-PKcs activation in cSCC cells. Significantly, restoring DNA-PKcs activation by a constitutively active-DNA-PKcs (S2056D) partially inhibited GDC-0084-induced cell death and apoptosis in A431 cells. In vivo, GDC-0084 daily gavage potently inhibited A431 xenograft tumor growth in mice. In GDC-0084-treated tumor tissues PI3K-Akt-mTOR and DNA-PKcs activation were significantly inhibited. In summary, GDC-0084 inhibits human cSCC cell growth in vitro and in vivo through blocking PI3K-Akt-mTOR and DNA-PKcs signalings.

Targeting sphingosine kinase 2 by ABC294640 inhibits human skin squamous cell carcinoma cell growth

The activity of ABC294640, a small-molecular sphingosine kinase 2 (SphK2) inhibitor, in human skin squamous cell carcinoma (SCC) cells was tested in this study. SphK2 mRNA and protein are expressed in established (A431 cheilocarcinoma cell line) and primary human skin SCC cells. ABC294640 dose-dependently inhibited survival, cell cycle progression and proliferation of skin SCC cells. Furthermore, ABC294640 induced caspase-3/-9 and apoptosis activation in skin SCC cells. The SphK2 inhibitor was however non-cytotoxic to SphK2-null skin melanocytes, keratinocytes and fibroblasts. ABC294640 induced ceramide accumulation, sphingosine-1-phosphate (S1P) reduction, Akt-S6K1 inhibition and JNK activation in skin SCC cells. Conversely, its cytotoxicity against SCC cells was largely attenuated by co-treatment of S1P, the Akt activator SC79, and the JNK inhibitor SP600125. In vivo, ABC294640 oral administration inhibited A431 xenograft tumor growth in nude mice. Akt-S6K1 inhibition and JNK activation were observed in ABC294640-treated tumors. Collectively, ABC294640 efficiently inhibits human skin SCC cell growth in vitro and in vivo.

Sphingosine metabolism as a therapeutic target in cutaneous melanoma

Melanoma is by far the most aggressive type of skin cancer with a poor prognosis in its advanced stages. Understanding the mechanisms involved in melanoma pathogenesis, response, and resistance to treatment has gained a lot of attention worldwide. Recently, the role of sphingolipid metabolism has been studied in cutaneous melanoma. Sphingolipids are bioactive lipid effector molecules involved in the regulation of various cellular signaling pathways such as inflammation, cancer cell proliferation, death, senescence, and metastasis. Recent studies suggest that sphingolipid metabolism impacts melanoma pathogenesis and is a potential therapeutic target. This review focuses on defining the role of sphingolipid metabolism in melanoma carcinogenesis, discussing sphingolipid-based therapeutic approaches, and highlighting the areas that require more extensive research.

Preclinical study of CC223 as a potential anti-ovarian cancer agent

Aberrant activation of mTOR contributes to ovarian cancer progression. CC223 is a novel and potent mTOR kinase inhibitor. The current study tested its activity against human ovarian cancer cells. We showed that CC223, at nM concentrations, inhibited survival and proliferation of established/primary human ovarian cancer cells. Further, significant apoptosis activation was observed in CC223-treated ovarian cancer cells. CC223 disrupted assembly of mTOR complex 1 (mTORC1) and mTORC2 in SKOV3 cells. Meanwhile, activation of mTORC1 and mTORC2 was almost completely blocked by CC223. Intriguingly, restoring mTOR activation by introduction of a constitutively-active Akt1 only partially inhibited CC223-induced cytotoxicity in SKOV3 cells. Further studies showed that CC223 inhibited sphingosine kinase 1 (SphK1) activity and induced reactive oxygen species (ROS) production in SKOV3 cells. At last, oral administration of CC223 potently inhibited SKOV3 xenografted tumor growth in nude mice. The results of this study imply that CC223 could be further studied as a potential anti-ovarian cancer agent.

AMPK activation by GSK621 inhibits human melanoma cells in vitro and in vivo

Recent studies suggest that forced activation of AMP-activated protein kinase (AMPK) could inhibit melanoma cell proliferation. In this report, we evaluated the anti-melanoma cell activity by a novel small-molecular AMPK activator, GSK621. Treatment of GSK621 decreased survival and proliferation of human melanoma cells (A375, WM-115 and SK-Mel-2 lines), which was accompanied by activation of caspase-3/-9 and apoptosis. Reversely, caspase inhibitors attenuated GSK621-induced cytotoxicity against melanoma cells. Significantly, GSK621 was more potent than other AMPK activators (A769662, Compound 13 and AICAR) in inhibiting melanoma cells. Intriguingly, same GSK621 treatment was non-cytotoxic or pro-apoptotic against human melanocytes. Molecularly, we showed that activation of AMPK mediated GSK621's activity against melanoma cells. AMPKα1 shRNA knockdown or dominant negative mutation (T172A) dramatically attenuated GSK621-induced melanoma cell lethality. Further studies revealed that MEK-ERK activation might be the primary resistance factor of GSK621. MEK-ERK inhibition, either genetically or pharmacologically, significantly sensitized melanoma cells to GSK-621. Remarkably, intraperitoneal (i.p.) injection of GSK621 inhibited A375 tumor growth in SCID mice. Co-administration of MEK-ERK inhibitor MEK162 further sensitized GSK621-induced anti-A375 tumor activity in vivo. Together, the results imply that targeted activation of AMPK by GSK621 inhibits melanoma cell survival and proliferation. MEK-ERK inhibition may further sensitize GSK621's anti-melanoma cell activity in vitro and in vivo.