Differentiating the Mechanistic Role and Chemotherapeutic Potential of SRC and Podoplanin in Oncogenic Transformation

There were an estimated 20 million new cancer cases worldwide in 2020, resulting in nearly 1000 deaths per hour [1]. Oral cancer exemplifies the difficulties of treating cancer patients. The first line for oral cancer treatment is surgery and radiation that can lead to patient disfigurement and decreased quality of life in cancer survivors [2-4]. Though there have been many developments in chemotherapy in the last 30 years, the 50% mortality rate associated with oral cancer has not changed [4, 5]. Longitudinal studies that track survival rates in oral cancer patients demonstrate a 3-fold reduction in patient deaths when patients are diagnosed with stage 1 through 3 tumors as opposed to stage 4 and beyond [5]. This indicates that we need to understand the stages of tumor development to find early-stage biomarkers that can be exploited as chemotherapeutic targets. The transmembrane receptor Podoplanin (Pdpn) has become a functionally relevant biomarker and chemotherapeutic target [6-8]. Pdpn is not typically expressed in oral epithelia; however, when Pdpn expression arises in oral cancer development, there is a 3-to-4-fold drop in 5-year patient survival [9]. Pdpn expression can be induced by oncogenes including the Src nonreceptor tyrosine kinase to promote cancer cell migration and metastasis [10-12]. In these studies, we demonstrate that Src and Pdpn promote cell anchorage independent cell growth and migration through independent mechanisms. We further elucidate the molecular pathways downstream that are altered when Pdpn is phosphorylated or targeted by extracellular agents. Recent work demonstrates that Maackia amurensis seed lectin (MASL) inhibits the cell migration and viability of Pdpn expressing melanoma cells [13]. We describe the chemotherapeutic potential and pleotropic effects of MASL in Pdpn expressing human oral squamous cell carcinoma (OSCC). Finally, we show that MASL has potential as an effective antiviral and anti-inflammatory agent that prevents the SARS-CoV-2 virus from binding host oral squamous cells. Together, these data suggest that Src and Pdpn induce discreet pathways to promote tumor development and these mechanisms can be targeted with MASL

Evidence that Maackia amurensis seed lectin (MASL) exerts pleiotropic actions on oral squamous cells with potential to inhibit SARS-CoV-2 infection and COVID-19 disease progression

COVID-19 was declared an international public health emergency in January, and a pandemic in March of 2020. There are over 125 million confirmed COVID-19 cases that have caused over 27 million deaths worldwide as of March 2021. COVID-19 is caused by the SARS-CoV-2 virus. SARS-CoV-2 presents a surface “spike” protein that binds to the ACE2 receptor to infect host cells. In addition to the respiratory tract, SARS-Cov-2 can also infect cells of the oral mucosa, which also express the ACE2 receptor. The spike and ACE2 proteins are highly glycosylated with sialic acid modifications that direct viral-host interactions and infection. Maackia amurensis seed lectin (MASL) has a strong affinity for sialic acid modified proteins and can be used as an antiviral agent. Here, we report that MASL targets the ACE2 receptor, decreases ACE2 expression and glycosylation, suppresses binding of the SARS-CoV-2 spike protein, and decreases expression of inflammatory mediators by oral epithelial cells that cause ARDS in COVID-19 patients. In addition, we report that MASL also inhibits SARS-CoV-2 infection of kidney epithelial cells in culture. This work identifies MASL as an agent with potential to inhibit SARS-CoV-2 infection and COVID-19 related inflammatory syndromes

PKA and CDK5 Can Phosphorylate Specific Serines on the Intracellular Domain of Podoplanin (PDPN) to Inhibit Cell Motility.

Podoplanin (PDPN) is a transmembrane glycoprotein that promotes tumor cell migration, invasion, and cancer metastasis. In fact, PDPN expression is induced in many types of cancer. Thus, PDPN has emerged as a functionally relevant cancer biomarker and chemotherapeutic target. PDPN contains 2 intracellular serine residues that are conserved between species ranging from mouse to humans. Recent studies indicate that protein kinase A (PKA) can phosphorylate PDPN in order to inhibit cell migration. However, the number and identification of specific residues phosphorylated by PKA have not been defined. In addition, roles of other kinases that may phosphorylate PDPN to control cell migration have not been investigated. We report here that cyclin dependent kinase 5 (CDK5) can phosphorylate PDPN in addition to PKA. Moreover, results from this study indicate that PKA and CDK5 cooperate to phosphorylate PDPN on both intracellular serine residues to decrease cell motility. These results provide new insight into PDPN phosphorylation dynamics and the role of PDPN in cell motility. Understanding novel mechanisms of PDPN intracellular signaling could assist with designing novel targeted chemotherapeutic agents and procedures

Low Molecular Weight Components in Aqueous Echinacea Purpurea Leaf Extract Inhibit Melanoma Cell Growth

Melanoma is a skin cancer associated with high mortality. The three year survival rate from advanced melanoma is between 10-15%. One reason for this high mortality rate is that melanoma cells are resistant to traditional chemotherapeutics. Echinacea is a plant genus native to North America with putative anticancer properties. Here, we examined effects of aqueous Echinacea purpurea leaf extract on the growth of melanoma cells and nontransformed fibroblasts. This aqueous extract reduced B16 mouse melanoma cell growth at concentrations that did not inhibit the growth of nontransformed NIH3T3 fibroblasts, suggesting that the extract had biological specificity against transformed cells. We also examined the effect of different fractions of the extract on melanoma cell growth. These data indicate that components less than 3 kD in size exhibited the greatest inhibitory action on melanoma cell growth. In addition, these data indicated that larger components in the extract ameliorate the ability of these low molecular weight compounds to inhibit melanoma cell growth. Furthermore, Echinacea extract inhibited the growth of v-Src transformed LA25 cells without reducing Src kinase activity. Taken together, these results suggest that aqueous Echinacea purpurea extract contains low molecular weight compounds that preferentially inhibit tumor cell growth in the face of oncogenic tyrosine kinase activity. These data suggest future studies to better define bioactive compounds in Echinacea purpurea and evaluate their therapeutic efficacy in vivo

Podoplanin: An Emerging Cancer Biomarker and Therapeutic Target

Podoplanin (PDPN) is a transmembrane receptor glycoprotein that is upregulated on transformed cells, cancer associated fibroblasts and inflammatory macrophages that contribute to cancer progression. In particular, PDPN increases tumor cell clonal capacity, epithelial mesenchymal transition, migration, invasion, metastasis and inflammation. Antibodies, CAR-T cells, biologics and synthetic compounds that target PDPN can inhibit cancer progression and septic inflammation in preclinical models. This review describes recent advances in how PDPN may be used as a biomarker and therapeutic target for many types of cancer, including glioma, squamous cell carcinoma, mesothelioma and melanoma

Components in aqueous Hibiscus rosa-sinensis flower extract inhibit in vitro melanoma cell growth

Skin cancer is extremely common, and melanoma causes about 80% of skin cancer deaths. In fact, melanoma kills over 50 thousand people around the world each year, and these numbers are rising. Clearly, standard treatments are not effectively treating melanoma, and alternative therapies are needed to address this problem. Hibiscus tea has been noted to have medicinal properties, including anticancer effects. Extracts from Hibiscus have been shown to inhibit the growth of a variety of cancer cells. In particular, recent studies found that polyphenols extracted from Hibiscus sabdariffa by organic solvents can inhibit melanoma cell growth. However, effects of aqueous extracts from Hibiscus rosa-sinesis flowers, which are commonly used to make traditional medicinal beverages, have not been examined on melanoma cells. Here, we report that aqueous H. rosa-sinesis flower extract contains compounds that inhibit melanoma cell growth in a dose dependent manner at concentrations that did not affect the growth of nontransformed cells. In addition, these extracts contain low molecular weight growth inhibitory compounds below 3 kD in size that combine with larger compounds to more effectively inhibit melanoma cell growth. Future work should identify these compounds, and evaluate their potential to prevent and treat melanoma and other cancers

Podoplanin emerges as a functionally relevant oral cancer biomarker and therapeutic target.

Oral cancer has become one of the most aggressive types of cancer, killing 140,000 people worldwide every year. Current treatments for oral cancer include surgery and radiation therapies. These procedures can be very effective; however, they can also drastically decrease the quality of life for survivors. New chemotherapeutic treatments are needed to more effectively combat oral cancer. The transmembrane receptor podoplanin (PDPN) has emerged as a functionally relevant oral cancer biomarker and chemotherapeutic target. PDPN expression promotes tumor cell migration leading to oral cancer invasion and metastasis. Here, we describe the role of PDPN in oral squamous cell carcinoma progression, and how it may be exploited to prevent and treat oral cancer

Podoplanin: An emerging cancer biomarker and therapeutic target

Podoplanin (PDPN) is a transmembrane receptor glycoprotein that is upregulated on transformed cells, cancer associated fibroblasts and inflammatory macrophages that contribute to cancer progression. In particular, PDPN increases tumor cell clonal capacity, epithelial mesenchymal transition, migration, invasion, metastasis and inflammation. Antibodies, CAR-T cells, biologics and synthetic compounds that target PDPN can inhibit cancer progression and septic inflammation in preclinical models. This review describes recent advances in how PDPN may be used as a biomarker and therapeutic target for many types of cancer, including glioma, squamous cell carcinoma, mesothelioma and melanoma.Funding Agencies|Proteintech; Fox Rothschild; VWR; Sentrimed; Rowan University; Osteopathic Heritage Foundation; New Jersey Health Foundation; JSPS KAKENHI [25461674, 24659185, 16H05311, 2617H06356]; National Cancer Center Research and Development Fund [23-A-12]; Foundation for the Promotion of Cancer Research; 3rd Term Comprehensive 10-Year Strategy for Cancer Control; Advanced Research for Medical Products Mining Programme of the National Institute of Biomedical Innovation (NIBIO); British Heart Foundation [RG/13/18/30563]; Project for Cancer Research and Therapeutic Evolution (P-CREATE) [17cm0106205 h0002]; Medical Research and Development Programs Focused on Technology Transfer, Acceleration Transformative Research for Medical Innovation (ACT-MS) from the Japan Agency for Medical Research and Development (AMED) [17im0210607 h0002]</p