Christopher Ong

Breast cancer (BCa) is a significant cause of cancer-related deaths among females globally. Approximately 45% of BCa patients develop treatment resistance or suffer from a lack of targeted therapies. Previously, we have shown that Semaphorin 3C (SEMA3C) is an autocrine growth factor that drives the growth and treatment resistance of various cancers. This study aims to investigate the functional role of SEMA3C in breast cancer progression and treatment resistance. My analysis of clinical datasets revealed elevated levels of SEMA3C mRNA in breast tumors compared to normal adjacent tissue. SEMA3C expression was positively correlated with the expression of various oncogenes implicated in breast cancer. Both estrogen receptor (ER) positive (ER⁺/HER2ˉ) BCa and triple negative breast cancer (TNBC) cells exhibited higher levels of SEMA3C protein compared to a non-cancer mammary epithelial cell line (MCF10A). Stimulation with recombinant SEMA3C activated EGFR, MAPK and AKT signaling in both ER⁺ and TNBC cells. Conversely, SEMA3C silencing inhibited ER expression, EGFR, MAPK, and AKT signaling, while inducing apoptosis. Silencing of SEMA3C significantly suppressed the growth of ER⁺ BCa and TNBC cells, indicating a growth dependency on SEMA3C. Tamoxifen-resistant cells (TamC3, TamR3) remained reliant on SEMA3C for growth and survival, suggesting its persistence in treatment resistance. Additionally, SEMA3C suppression enhanced the efficacy of certain chemotherapies and targeted therapies in TNBC cells. Additionally, treatment with SEMA3C pathway inhibitors, B1SP (Fc fusion protein) and ALS, attenuated SEMA3C-induced signaling and growth in both ER⁺ and TNBC cells. This study highlights the functional role of SEMA3C in breast cancer signaling and growth, suggesting its potential as a therapeutic target. Targeting SEMA3C may offer benefits in improving treatment outcomes for breast cancer patients, particularly in cases of endocrine treatment resistance and TNBC.

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Androgens i.e. testosterone (T) and dihydrotestosterone (DHT), have essential roles in the differentiation and growth of normal prostate cells, as well as in the progression of prostate cancer (PCa) cells. Androgen deprivation therapy (ADT) is an effective therapy for PCa patients, however, prostate tumor cells progress to a treatment-resistant stage known as castration-resistant prostate cancer (CRPC). It has been established that CRPC cells have an acquired ability to synthesize androgens to resist the systemic androgen depletion imposed by ADT. This autonomous steroidogenesis in tumor cells, known as intratumoral steroidogenesis, provides a sufficient androgen level for their survival and growth. Discovering the gene networks or signaling pathways capable of upregulating intratumoral steroidogenesis is a major challenge in PCa research.Our laboratory studies the potential role of Semaphorin 3C (SEMA3C) in CRPC progression. This secreted signaling protein has been implicated in multiple cancer types, including PCa. Our previous findings showed SEMA3C’s potent ability to trigger receptor tyrosine kinase (RTK) signaling pathways independent to cognate ligand-binding, SEMA3C’s increased expression in CRPC bone metastasis, and also SEMA3C’s capability to promote epithelial-to-mesenchymal transition and stem-like characteristics.In the present work, we investigated whether SEMA3C is able to affect steroidogenesis from various substrates in epithelial PCa cells, and also in prostatic stromal cells, both of which can contribute to the synthesis of androgenic steroids in the tumor microenvironment. Work presented here demonstrates that SEMA3C can support androgen maintenance in prostate tumor cells in an androgen-deprived environment, byivdownregulating genes in the DHT inactivation pathway that irreversibly terminates the signal of this androgen receptor (AR) ligand. In parallel, SEMA3C upregulates genes coding for enzymes involved in T and DHT synthesis from cholesterol (de novo synthesis) or from circulatory adrenal hormones such as dehydroepiandrosterone (DHEA) (defined as derivative synthesis). We also observed that SEMA3C can alter expression of lipogenic or cholesterogenic genes by influencing sterol regulatory element binding proteins (SREBP) transcriptional activity. Collectively, findings of this study show that SEMA3C’s ability to increase androgen synthesis can contribute to castration-resistant growth of PCa cells in androgen-depleted environments as observed in our CRPC progression model.

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Prostate cancer (PCa) is among the most commonly-occurring cancers worldwide and a leading cause of cancer-related deaths in men. Local non-invasive PCa is highly treatable but limited treatment options exist for those with locally-advanced and metastatic forms of the disease. This underscores the need to identify mechanisms mediating PCa progression. One well-established driver of PCa progression is the androgen receptor protein whose transcriptional targets include genes related to cell growth and cell cycle progression. Consequently, the androgen receptor axis is the target of many therapies for those with PCa. Another important aspect of disease progression relates to cancer spread or metastasis. Epithelial-to-mesenchymal transition (EMT) is a cellular process executed during embryogenesis and is defined as the transition of cells from an epithelial phenotype to a mesenchymal phenotype. It is suspected that metastasis is, in part, due to inadvertent re-activation of EMT. Another theorized cause of cancer progression is due to the existence of tumour-initiating cells or ‘cancer stem cells’ which resist conventional radiation- and chemotherapies and seed relapse and metastasis.The semaphorins are a large grouping of membrane-associated or s¬ecreted signalling proteins whose normal roles reside in embryogenesis and neuronal development. During these processes the semaphorins establish chemotactic gradients and direct cell movement. Various semaphorin family members have been found to be up- or downregulated in a number of cancers. One family member, semaphorin 3C (SEMA3C), has been implicated in several types of cancer and its increased expression is correlated with PCa stage. Given SEMA3C’s roles in development and its augmented expression in PCa, we hypothesized that SEMA3C promotes cancer progression by driving EMT and stem-like characteristics. In the present study, we show that SEMA3C is a direct transcriptional target of the androgen receptor and further show that ectopic expression of SEMA3C in RWPE-1, a normal prostate epithelial cell line, leads to an upregulation of EMT and stem markers which is accompanied by acquisition of invasiveness and stem-like phenotypes. The broader impact of this work pertains to the clinical implications of SEMA3C’s involvement in PCa and linking SEMA3C and AR to metastatic recurrent PCa.

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Cutaneous melanoma is a life-threatening skin cancer due to its poorly understood invasivnature and high metastatic potential. On the other hand, translational dysregulation has been shown to have an important role in the development and progression of cancer. In this study we investigated the role of two translational factors called eukaryotic translation initiation factor 5A2 (EIF5A2) and eukaryotic translation initiation factor 4E (eIF4E) in melanoma. Using tissue microarray (TMA) we showed that eIF4E expression and nuclear and cytoplasmic EIF5A2 expression increased from dysplastic nevi to primary melanomas, and further increased in metastatic melanomas. The expression of eIF4E and both EIF5A2 forms were correlated with melanoma thickness and AJCC stages and were inversely correlated with the 5-year survival of melanoma patients. TMA data also revealed that nuclear EIF5A2, cytoplasmic EIF5A2 and eIF4E expression were all directly correlated with MMP-2 expression which is an important factor for promoting cancer cell invasion. In addition, in vitro analysis revealed that both melanoma cell invasion and MMP-2 activity decreased as a result of EIF5A2 or eIF4E knockdown indicating that EIF5A2 and eIF4E may be responsible for increasing melanoma cellinvasiveness at least partly through increasing MMP-2 activity. Our experiments also showed that EIF5A2 is a novel downstream target of p-Akt. Additionally, we indicated that both EIF5A2 and eIF4E may play a role in EMT by upregulating mesenchymal markers and downregulating epithelial markers. eIF4E knockdown also decreased cell proliferation and increased apoptosis and caused a decrease in c-myc and BCL-2 expression, and an increase in cleaved PARP and cleaved caspase-3 expression and chemosensitivity. Nuclear and cytoplasmic EIF5A2 expression were found to be significantly correlated, and simultaneous expression of both was significantly associated with poor overall and disease-specific 5-year survival of melanoma patients. This correlation; however, was not perfect which may indicate the differential regulation of nuclear and cytoplasmic EIF5A2 expression in melanoma. Multivariate Cox regression analysis revealed that eIF4E expression, nuclear and cytoplasmic EIF5A2 expression and the combination of the last two were an adverse independent prognostic factor for melanoma patients. Therefore, they have the potential to be used as prognostic therapeutic markers in melanoma.

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Cutaneous melanoma remains to be not only one of the most deadly among all skin cancers, but it’s one of the most deadly of all cancers in general. It is crucial to have an early detection of the disease despite lacking any effective treating options while therapeutic strategies of later stages of melanoma have yet to be discovered. Meanwhile, the mechanism modulating the progression of melanoma is still not well understood. In this study, we investigated KAI1’s role during metastasis regulation in human melanoma. We proposed the tumor suppressor function of KAI1 was directly correlated with KAI1 expression and showed the loss of KAI1 expression in melanoma patient samples significantly correlated with poorer patient survival. Furthermore, forced KAI1 expression was shown to suppress melanoma cell migration and invasion primarily through its regulation of another tumor suppressor gene: inhibitor of growth 4 (ING4). Moreover, KAI1 expression significantly suppressed melanoma angiogenesis by reducing HUVEC cell growth and tubular structure formation. In fact, KAI1’s regulation on angiogenesis was associated with the modulation of IL-6 and VEGF expression. Additionally, we investigated the mechanistic pathway between KAI1 and ING4 and found that KAI1 suppressed Akt phosphorylation through the regulation of EGFR and VEGFR phosphorylation. Meanwhile, the semaphorin 3C (SEMA3C) protein had been identified as an oncogene that induced cancer cell migration and invasion. In this study, we found that SEMA3C was also able to induce melanoma angiogenesis observed in the elevated HUVEC growth and tube formation. Furthermore, we showed that KAI1 expression suppressed SEMA3C-induced melanoma angiogenesis whereas KAI1 knockdown rescued the SEAM3C-suppressed melanoma angiogenesis. According to our study, we have illustrated a regulatory pathway of KAI1 on the regulation of melanoma metastasis which involves the regulation of the PI3K/Akt pathway and the tumor suppressor gene ING4. Also, the restoration of KAI1 expression was shown to significantly suppress melanoma cancer cell migration, invasion and angiogenesis. Taken together, KAI1 was a potential diagnostic marker for advanced melanoma and the restoration of KAI1 expression might shed light on new therapeutic approaches for treating cutaneous human melanoma.

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No abstract available.