Ugo Cavallaro

Navitoclax, a Bcl-2/xL Inhibitor, and YM155, a Survivin Inhibitor, in Combination with Carboplatin, Effectively Inhibit Ovarian Cancer Tumor Growth

Abstract High-grade serous ovarian cancer is generally treated with upfront chemotherapy, including carboplatin. The persistence of platinum-resistant cells drives recurrent disease. A high-throughput screen using a 3D organotypic culture assembled with extracellular matrix, primary human fibroblasts, and mesothelial cells was established and validated. Using a library of FDA-approved drugs, the 3D high-throughput screen was performed with the goal of identifying a combination of drugs that synergistically target two populations of ovarian cancer: aldehyde dehydrogenase (ALDH) high (ALDHhi) and ALDH low (ALDHlo) enzyme activity cells, which are less sensitive to carboplatin treatment than the bulk ovarian cancer cells. Initial results showed that omipalisib, verteporfin, CA3, mitoxantrone, navitoclax, venetoclax, and YM155 had significant single-drug activity in either the ALDHlo or both the ALDHlo/ALDHhi cell populations. Synergistic drug activity was identified with three drug combinations: navitoclax/omipalisib, navitoclax/YM155, and YM155/omipalisib. In vitro, the combination of navitoclax/YM155 was most efficient at blocking primary human ovarian cancer sphere formation and the proliferation of four different ovarian cancer cell lines in the 3D organotypic culture. In vivo, the combination of navitoclax/YM155/carboplatin decreased ovarian cancer metastasis, decreased the percentage of ALDHhi ovarian cancer cells in tumors, and increased survival when compared with carboplatin treatment alone in xenograft models. Our results suggest that the combination of navitoclax/YM155/carboplatin has promise as a therapy for treating ovarian cancer.

Tumor microenvironment-induced FOXM1 regulates ovarian cancer stemness

AbstractIn ovarian tumors, the omental microenvironment profoundly influences the behavior of cancer cells and sustains the acquisition of stem-like traits, with major impacts on tumor aggressiveness and relapse. Here, we leverage a patient-derived platform of organotypic cultures to study the crosstalk between the tumor microenvironment and ovarian cancer stem cells. We discovered that the pro-tumorigenic transcription factor FOXM1 is specifically induced by the microenvironment in ovarian cancer stem cells, through activation of FAK/YAP signaling. The microenvironment-induced FOXM1 sustains stemness, and its inactivation reduces cancer stem cells survival in the omental niche and enhances their response to the PARP inhibitor Olaparib. By unveiling the novel role of FOXM1 in ovarian cancer stemness, our findings highlight patient-derived organotypic co-cultures as a powerful tool to capture clinically relevant mechanisms of the microenvironment/cancer stem cells crosstalk, contributing to the identification of tumor vulnerabilities.

L1CAM promotes ovarian cancer stemness and tumor initiation via FGFR1/SRC/STAT3 signaling

Abstract Background Cancer stem cells (CSC) have been implicated in tumor progression. In ovarian carcinoma (OC), CSC drive tumor formation, dissemination and recurrence, as well as drug resistance, thus contributing to the high death-to-incidence ratio of this disease. However, the molecular basis of such a pathogenic role of ovarian CSC (OCSC) has been elucidated only to a limited extent. In this context, the functional contribution of the L1 cell adhesion molecule (L1CAM) to OC stemness remains elusive. Methods The expression of L1CAM was investigated in patient-derived OCSC. The genetic manipulation of L1CAM in OC cells provided gain and loss-of-function models that were then employed in cell biological assays as well as in vivo tumorigenesis experiments to assess the role of L1CAM in OC cell stemness and in OCSC-driven tumor initiation. We applied antibody-mediated neutralization to investigate L1CAM druggability. Biochemical approaches were then combined with functional in vitro assays to study the molecular mechanisms underlying the functional role of L1CAM in OCSC. Results We report that L1CAM is upregulated in patient-derived OCSC. Functional studies showed that L1CAM promotes several stemness-related properties in OC cells, including sphere formation, tumor initiation and chemoresistance. These activities were repressed by an L1CAM-neutralizing antibody, pointing to L1CAM as a druggable target. Mechanistically, L1CAM interacted with and activated fibroblast growth factor receptor-1 (FGFR1), which in turn induced the SRC-mediated activation of STAT3. The inhibition of STAT3 prevented L1CAM-dependent OC stemness and tumor initiation. Conclusions Our study implicate L1CAM in the tumorigenic function of OCSC and point to the L1CAM/FGFR1/SRC/STAT3 signaling pathway as a novel driver of OC stemness. We also provide evidence that targeting this pathway can contribute to OC eradication.

Integrated molecular profiling of patient‐derived ovarian cancer models identifies clinically relevant signatures and tumor vulnerabilities

AbstractHigh‐grade serous ovarian carcinoma (HGSOC) is a highly aggressive and intractable neoplasm, mainly because of its rapid dissemination into the abdominal cavity, a process that is favored by tumor‐associated peritoneal ascites. The precise molecular alterations involved in HGSOC onset and progression remain largely unknown due to the high biological and genetic heterogeneity of this tumor. We established a set of different tumor samples (termed the As11‐set) derived from a single HGSOC patient, consisting of peritoneal ascites, primary tumor cells, ovarian cancer stem cells (OCSC) and serially propagated tumor xenografts. The As11‐set was subjected to an integrated RNA‐seq and DNA‐seq analysis which unveiled molecular alterations that marked the different types of samples. Our profiling strategy yielded a panel of signatures relevant in HGSOC and in OCSC biology. When such signatures were used to interrogate the TCGA dataset from HGSOC patients, they exhibited prognostic and predictive power. The molecular alterations also identified potential vulnerabilities associated with OCSC, which were then tested functionally in stemness‐related assays. As a proof of concept, we defined PI3K signaling as a novel druggable target in OCSC.

Quantitative Proteomics and Phosphoproteomics Analysis of Patient-Derived Ovarian Cancer Stem Cells

High-grade serous ovarian carcinoma (HGSOC) is the deadliest gynecologic cancer. Key to the progression and ultimate lethality of this subtype is the intra-tumoral heterogeneity, which is defined as the coexistence of different cell types and populations within a single tumor. Among those, ovarian cancer stem cells (OCSCs) are a distinct subpopulation of tumor cells endowed with stem-like properties, which can survive current standard therapies, resulting in tumor recurrence. Here, we generated ex vivo primary OCSC-enriched three-dimensional (3D) spheres from 10 distinct treatment naive patient-derived adherent (2D) cultures. We used state-of-the-art quantitative mass spectrometry to characterize the molecular events associated with OCSCs by analyzing their proteome and phosphoproteome. Our data revealed a stemness-related protein signature, shared within a heterogeneous patient cohort, which correlates with chemo-refractoriness in a clinical proteomics dataset. Moreover, we identified targetable deregulated kinases and aberrant PDGF receptor activation in OCSCs. Pharmacological inhibition of PDGFR in adherent OC cells reduced the stemness potential, measured by sphere formation assay. Overall, we provide a valuable resource to identify new OCSC markers and putative targets for OCSC-directed therapies.