Ratna K. Vadlamudi

The PELP1 Pathway and Its Importance in Cancer Treatment

Proline-, glutamic acid-, and leucine-rich protein 1 (PELP1) is a proto-oncogene that serves as a nuclear and cytoplasmic scaffolding protein. PELP1 plays a critical role in nuclear receptor signaling, ribosome biogenesis, chromatin modifications, cell cycle progression, non-genomic signaling, and DNA damage response. PELP1 expression is upregulated in a variety of cancers, including breast, ovarian, endometrial, prostate, and liver cancers and serves as a prognostic factor for poor survival. PELP1’s structural motifs, unique scaffolding function, and oncogenic activity make it a potential target for a range of therapeutic approaches. This review summarizes the most recent advancements in PELP1 biology, with a particular focus on the emergent oncogenic functions of PELP1 and its inhibitors for the treatment of cancer.

EC359 Enhances Trametinib Efficacy in Ras/Raf-Driven Ovarian Cancer by Suppressing LIFR Signaling

Ovarian cancer (OCa) remains the most lethal gynecologic malignancy in the United States, with low-grade serous and mucinous subtypes frequently driven by KRAS mutations. These mutations activate downstream MAPK and PI3K/AKT signaling pathways, contributing to tumor progression and resistance to therapy. Although the MEK inhibitor trametinib is used to target these pathways, its efficacy is limited in KRAS-mutant OCa due to compensatory activation of the leukemia inhibitory factor (LIF)/LIF receptor (LIFR) axis. In this study, we evaluated the therapeutic potential of combining trametinib with EC359, a selective LIFR inhibitor, in Ras/Raf-driven OCa models. EC359 significantly reduced cell viability, clonogenic survival, and induced cell death via ferroptosis in vitro. Mechanistic studies revealed that EC359 suppressed trametinib-induced activation of LIFR downstream signaling. RNA-seq analysis showed that combination therapy downregulated mitochondrial translation and MYC target genes while upregulating apoptosis-related genes. In vivo, EC359 and trametinib co-treatment significantly reduced tumor growth in xenograft and PDX models without inducing toxicity. Our studies identify LIFR signaling as a critical vulnerability in Ras/Raf-mutant and low grade serous OCa. Further, it provides strong preclinical rationale for EC359 and trametinib combination therapy as a new therapeutic strategy for treating Ras/Raf-driven OCa and low-grade serous OCa.

PELP1 inhibition by SMIP34 reduces endometrial cancer progression via attenuation of ribosomal biogenesis

Endometrial carcinoma (ECa) is the fourth most common cancer among women. The oncogene PELP1 is frequently overexpressed in a variety of cancers, including ECa. We recently generated SMIP34, a small‐molecule inhibitor of PELP1 that suppresses PELP1 oncogenic signaling. In this study, we assessed the effectiveness of SMIP34 in treating ECa. Treatment of established and primary patient‐derived ECa cells with SMIP34 resulted in a significant reduction of cell viability, colony formation ability, and induction of apoptosis. RNA‐seq analyses showed that SMIP34‐regulated genes were negatively correlated with ribosome biogenesis and eukaryotic translation pathways. Mechanistic studies showed that the Rix complex, which is essential for ribosomal biogenesis, is disrupted upon SMIP34 binding to PELP1 . Biochemical assays confirmed that SMIP34 reduced ribosomal biogenesis and new protein synthesis. Further, SMIP34 enhanced the efficacy of mTOR inhibitors in reducing viability of ECa cells. SMIP34 is also effective in reducing cell viability in ECa organoids in vitro and explants ex vivo . Importantly, SMIP34 treatment resulted in a significant reduction of the growth of ECa xenografts. Collectively, these findings underscore the potential of SMIP34 in treating ECa.

Bladder cancer cell‐intrinsic PD‐L1 signals promote mTOR and autophagy activation that can be inhibited to improve cytotoxic chemotherapy

AbstractTumor cell‐intrinsic programmed death‐ligand 1 (PD‐L1) signals mediate immunopathologic effects in breast, colon, and ovarian cancers and in melanomas, but bladder cancer (BC) effects are unreported. We show here that BC cell‐intrinsic PD‐L1 signals in mouse MB49 and human RT4, UM‐UC3, and UM‐UC‐14 BC cells regulate important pathologic pathways and processes, including effects not reported in other cancers. α‐PD‐L1 antibodies reduced BC cell proliferation in vitro, demonstrating direct signaling effects. BC cell‐intrinsic PD‐L1 promoted mammalian target of rapamycin complex 1 (mTORC1) signals in vitro and augmented in vivo immune‐independent cell growth and metastatic cancer spread, similar to effects we reported in melanoma and ovarian cancer. BC cell‐intrinsic PD‐L1 signals also promoted basal and stress‐induced autophagy, whereas these signals inhibited autophagy in melanoma and ovarian cancer cells. BC cell‐intrinsic PD‐L1 also mediated chemotherapy resistance to the commonly used BC chemotherapy agents cis‐platinum and gemcitabine and to the mTORC1 inhibitor, rapamycin. Thus, BC cell‐intrinsic PD‐L1 signals regulate important virulence and treatment resistance pathways that suggest novel, actionable treatment targets meriting additional studies. As a proof‐of‐concept, we showed that the autophagy inhibitor chloroquine improved cis‐platinum treatment efficacy in vivo, with greater efficacy in PD‐L1 null versus PD‐L1‐replete BC.

KDM1A/LSD1 inhibition enhances chemotherapy response in ovarian cancer

AbstractOvarian cancer (OCa) is the deadliest of all gynecological cancers. The standard treatment for OCa is platinum‐based chemotherapy, such as carboplatin or cisplatin in combination with paclitaxel. Most patients are initially responsive to these treatments; however, nearly 90% will develop recurrence and inevitably succumb to chemotherapy‐resistant disease. Recent studies have revealed that the epigenetic modifier lysine‐specific histone demethylase 1A (KDM1A/LSD1) is highly overexpressed in OCa. However, the role of KDM1A in chemoresistance and whether its inhibition enhances chemotherapy response in OCa remains uncertain. Analysis of TCGA datasets revealed that KDM1A expression is high in patients who poorly respond to chemotherapy. Western blot analysis show that treatment with chemotherapy drugs cisplatin, carboplatin, and paclitaxel increased KDM1A expression in OCa cells. KDM1A knockdown (KD) or treatment with KDM1A inhibitors NCD38 and SP2509 sensitized established and patient‐derived OCa cells to chemotherapy drugs in reducing cell viability and clonogenic survival and inducing apoptosis. Moreover, knockdown of KDM1A sensitized carboplatin‐resistant A2780‐CP70 cells to carboplatin treatment and paclitaxel‐resistant SKOV3‐TR cells to paclitaxel. RNA‐seq analysis revealed that a combination of KDM1A‐KD and cisplatin treatment resulted in the downregulation of genes related to epithelial‐mesenchymal transition (EMT). Interestingly, cisplatin treatment increased a subset of NF‐κB pathway genes, and KDM1A‐KD or KDM1A inhibition reversed this effect. Importantly, KDM1A‐KD, in combination with cisplatin, significantly reduced tumor growth compared to a single treatment in an orthotopic intrabursal OCa xenograft model. Collectively, these findings suggest that combination of KDM1A inhibitors with chemotherapy could be a promising therapeutic approach for the treatment of OCa.

Therapeutic optimization of LIPA targeting to induce endoplasmic reticulum stress and cell death in ovarian cancer

Ovarian cancer (OCa) remains the most lethal gynecologic malignancy in the United States, with a five-year survival rate below 20%. Elevated basal levels of endoplasmic reticulum stress (ERS) have recently emerged as a therapeutic vulnerability in OCa. We have previously shown that the tris-benzamide ERX-41 can induce ERS and cancer cell death in OCa by targeting LIPA. In this study, using iterative structure-activity relationship-guided studies to enhance activity in OCa, we identified a more potent ERX-41-derived analog, ERX-208. Importantly, ERX-208 consistently and significantly reduced cell viability in 23 OCa cell lines spanning five major histological OCa subtypes, with IC₅₀ values ranging from 50-100 nM, compared to ∼500 nM for ERX-41. Notably, ERX-208 showed minimal cytotoxicity toward normal ovarian surface epithelial cells, indicating cancer cell selectivity. ERX-208 induced apoptosis and suppressed colony formation in vitro in OCa cells. Mechanistic studies using RNA sequencing, Western blotting, RT-qPCR, transmission electron microscopy, and immunohistochemistry validated robust activation of ERS pathways upon ERX-208 treatment. Through in silico molecular docking simulation and confirmatory detailed site-directed mutagenesis, we identified that ERX-208 binds to LIPA over a broader interaction surface than ERX-41. At the 10 mg/kg dose, ERX-208 demonstrated favorable biodistribution, no observable toxicity, and potent antitumor efficacy in vivo against established cell line-derived xenograft (CDX), patient-derived xenograft (PDX), and patient-derived explant (PDE) models. Immunohistochemical analysis of treated tumors demonstrated changes in expression of proliferative marker (ki67, decreased) and the ERS marker (GRP78, increased). These findings support the clinical advancement of ERX-208 for the treatment of patients with OCa.