Predicting ROR1/BCL2 combination targeted therapy of small cell carcinoma of the lung

Small cell lung cancer (SCLC) remains a deadly form of cancer, with a 5-year survival rate of less than 10 percent, necessitating novel therapies. Receptor tyrosine kinase-like orphan receptor 1 (ROR1) is an oncofetal protein that is emerging as a therapeutic target and is co-expressed with BCL2 in multiple tumor types due to microRNA coregulation. We hypothesize that ROR1-targeted therapy is effective in small cell lung cancer and synergizes with therapeutic BCL2 inhibition. Tissue microarrays (TMAs) and formalin-fixed paraffin-embedded (FFPE) SCLC patient samples were utilized to determine the prevalence of ROR1 and BCL2 expression in SCLC. Eight SCLC-derived cell lines were used to determine the antitumor activity of a small molecule ROR1 inhibitor (KAN0441571C) alone and in combination with the BCL2 inhibitor venetoclax. The Chou-Talalay method was utilized to determine synergy with the drug combination. ROR1 and BCL2 protein expression was identified in 93% (52/56) and 86% (48/56) of SCLC patient samples, respectively. Similarly, ROR1 and BCL2 were shown by qRT-PCR to have elevated expression in 79% (22/28) and 100% (28/28) of SCLC patient samples, respectively. KAN0441571C displayed efficacy in 8 SCLC cell lines, with an IC50 of 500 nM or less. Synergy as defined by a combination index of <1 via the Chou-Talalay method between KAN0441571C and venetoclax was demonstrated in 8 SCLC cell lines. We have shown that ROR1 inhibition is synergistic with BCL2 inhibition in SCLC models and shows promise as a novel therapeutic target in SCLC.

Simultaneous paraneoplastic cerebellar degeneration, Lambert-Eaton syndrome and neuropathy associated with AGNA/anti-SOX1 and VGCC antibodies

Anti-glial nuclear antibody (AGNA) is an onconeuroal antibody targeting the nuclei of Bergmann glia in the cerebellum and Anti-SRY-related HMG-box 1 (SOX1). It is highly specific for small cell lung cancer (SCLC) and correlates to the appearance of paraneoplastic neurological syndromes such as Lambert-Eaton myasthenic syndrome (pLEMS) and paraneoplastic cerebellar degeneration (PCD) amongst others. Herein, we present a SCLC patient with rapidly progressive PCD, LEMS and axonal polyneuropathy associated with AGNA/SOX1-antibodies, successfully treated with plasma-exchange (PLEX).

Dysregulated Pyrimidine Biosynthesis Contributes to 5-FU Resistance in SCLC Patient-Derived Organoids but Response to a Novel Polymeric Fluoropyrimidine, CF10

Chemo-immunotherapy is central to the treatment of small cell lung cancer (SCLC). Despite modest progress made with the addition of immunotherapy, current cytotoxic regimens display minimal survival benefit and new treatments are needed. Thymidylate synthase (TS) is a well-validated anti-cancer drug target, but conventional TS inhibitors display limited clinical efficacy in refractory or recurrent SCLC. We performed RNA-Seq analysis to identify gene expression changes in SCLC biopsy samples to provide mechanistic insight into the potential utility of targeting pyrimidine biosynthesis to treat SCLC. We identified systematic dysregulation of pyrimidine biosynthesis, including elevated TYMS expression that likely contributes to the lack of efficacy for current TS inhibitors in SCLC. We also identified E2F1-3 upregulation in SCLC as a potential driver of TYMS expression that may contribute to tumor aggressiveness. To test if TS inhibition could be a viable strategy for SCLC treatment, we developed patient-derived organoids (PDOs) from human SCLC biopsy samples and used these to evaluate both conventional fluoropyrimidine drugs (e.g., 5-fluorouracil), platinum-based drugs, and CF10, a novel fluoropyrimidine polymer with enhanced TS inhibition activity. PDOs were relatively resistant to 5-FU and while moderately sensitive to the front-line agent cisplatin, were relatively more sensitive to CF10. Our studies demonstrate dysregulated pyrimidine biosynthesis contributes to drug resistance in SCLC and indicate that a novel approach to target these pathways may improve outcomes.

ASCL1-regulated DARPP-32 and t-DARPP stimulate small cell lung cancer growth and neuroendocrine tumor cell survival

Small cell lung cancer (SCLC) is the most aggressive form of lung cancer, and new molecular insights are necessary for prognostic and therapeutic advances. Here we demonstrate in orthotopic mouse models that dopamine and cAMP-regulated phosphoprotein, Mr 32000 (DARPP-32) and its N-terminally truncated splice variant t-DARPP promote SCLC growth through increased proliferation, Akt/Erk-mediated survival and anti-apoptotic signaling. DARPP-32 and t-DARPP proteins are overexpressed in SCLC patient-derived tumor tissue, but virtually undetectable in physiologically normal lung. RNA sequencing analysis reveals a subset of SCLC patients with high tumoral t-DARPP expression and upregulated Notch signaling genes, including achaete-scute homologue 1 (ASCL1). We show that DARPP-32 isoforms are transcriptionally activated by ASCL1 in human SCLC cells. Taken together, we demonstrate new regulatory mechanisms of SCLC oncogenesis that suggest DARPP-32 isoforms may represent a negative prognostic indicator for SCLC and serve as a potential target for the development of new therapies.