Myra Villareal

Plant-derived phytochemicals exhibit significant pharmacological potential in chronic diseases, including melanoma. Since hyperactive melanogenesis is closely linked to melanoma progression, targeting this pathway with natural bioactive agents represents a major therapeutic strategy. The plant-derived terpene linalool induces cancer-specific oxidative stress in colon cancer cells, as we have previously reported. Here, we characterized the effects of linalool on B16-F10 melanoma cells to establish a transcriptomic baseline of hypopigmentation networks using phenotypic assays and high-throughput RNA-seq profiling. Non-toxic doses of linalool significantly inhibited melanin synthesis, accompanied by a marked reduction in tyrosinase protein abundance. RNA-seq identified 31 significantly upregulated and 48 significantly downregulated genes (p < 0.05), with PCA and cluster analysis demonstrating a distinct transcriptomic profile. Functional GO enrichment revealed candidate regulatory networks involving lysosomal components, the neurofilament cytoskeleton, and cell-cycle checkpoints. While core melanogenesis transcripts (Mitf, Tyr, Dct) showed only minor, non-significant variations, key stress-adaptation and cell-plasticity regulators (Mir210, Dll1) were significantly suppressed. This profile indicates a state of latent molecular vulnerability, mirroring the oxidative responses in colon cancer cells. Taken together, these findings provide a foundational transcriptomic repository of linalool-responsive networks, uncovering critical candidate pathways that modulate melanin production and antioxidant defenses to guide future functional validation and therapeutic exploration of botanical bioactives in melanoma research.

Many ovarian cancers initially respond well to chemotherapy, but often become drug-resistant after several years. Therefore, analysis of drug resistance mechanisms and overcoming resistance are urgently needed. Paclitaxel is one of the first-choice and widely-used drugs for ovarian cancer, but like most drugs, drug resistance is observed in subsequent use. RSK4 is known as a tumor-suppressor, however, it has increasingly been reported to lead to drug resistance. Here, we found that RSK4 expression was elevated in paclitaxel-resistant ovarian cancer cells using DNA microarray, quantitative real-time PCR, and western blotting analysis. We examined the contribution of RSK4 to paclitaxel resistance and found that paclitaxel sensitivity was restored by RSK inhibitor co-treatment. We analyzed the mechanism by which resistance is developed when RSK4 level is elevated, and accelerated phosphorylation of the downstream translation factor eIF4B was discovered. In the Kaplan-Meier plot, the overall survival time was longer with RSK4 high, supporting its role as a tumor suppressor, as in previous findings, but the tendency was reversed when focusing on paclitaxel treatment. In addition, RSK4 levels were higher in non-responders than in responders in the ROC plotter. Finally, external expression of RSK4 in ovarian cancer cells increased the cell viability under paclitaxel treatment. These findings suggest that RSK4 may contribute to paclitaxel resistance, and that co-treatment with RSK4 inhibitors is effective treatment of paclitaxel-resistant ovarian cancer in which RSK4 is elevated.

Plant saponins are abundant and diverse natural products with a great potential for use in drug-discovery research. Here, we evaluated extracts of saponins-rich fractions of argan leaves and argan oil extraction byproducts (shell, pulp, press cake) for their effect on melanogenesis. Results show that from among the samples tested, only the saponins-rich fraction from leaves (ALS) inhibited melanin production in B16 murine melanoma (B16) cells. The mechanism of the melanogenesis inhibition was elucidated by determining the protein and mRNA expression of melanogenesis-associated enzymes tyrosinase (TYR), tyrosinase-related protein 1 (TRP1), and dopachrome tautomerase (DCT), and microphthalmia-associated transcription factor (MITF), and performing DNA microarray analysis. Results showed that 10 µg/mL ALS significantly inhibited melanogenesis in B16 cells and human epidermal melanocytes by 59% and 48%, respectively, without cytotoxicity. The effect of ALS on melanogenesis can be attributed to the decrease in TYR, TRP1, and MITF expression at the protein and mRNA levels. MITF inhibition naturally led to the downregulation of the expression of Tyr and Trp1 genes. Results of the DNA microarray analysis revealed the effect on melanogenesis-associated cAMP and Wnt signaling pathways’ genes. The results of this study suggest that ALS may be used in cosmeceuticals preparations for hyperpigmentation treatment.