BACKGROUND Cutaneous squamous-cell carcinomas and keratoacanthomas are common findings in patients treated with BRAF inhibitors. METHODS We performed a molecular analysis to identify oncogenic mutations (HRAS, KRAS, NRAS, CDKN2A, and TP53) in the lesions from patients treated with the BRAF inhibitor vemurafenib. An analysis of an independent validation set and functional studies with BRAF inhibitors in the presence of the prevalent RAS mutation was also performed. RESULTS Among 21 tumor samples, 13 had RAS mutations (12 in HRAS). In a validation set of 14 samples, 8 had RAS mutations (4 in HRAS). Thus, 60% (21 of 35) of the specimens harbored RAS mutations, the most prevalent being HRAS Q61L. Increased proliferation of HRAS Q61L–mutant cell lines exposed to vemurafenib was associated with mitogen-activated protein kinase (MAPK)–pathway signaling and activation of ERK-mediated transcription. In a mouse model of HRAS Q61L–mediated skin carcinogenesis, the vemurafenib analogue PLX4720 was not an initiator or a promoter of carcinogenesis but accelerated growth of the lesions harboring HRAS mutations, and this growth was blocked by concomitant treatment with a MEK inhibitor. CONCLUSIONS Mutations in RAS, particularly HRAS, are frequent in cutaneous squamous-cell carcinomas and keratoacanthomas that develop in patients treated with vemurafenib. The molecular mechanism is consistent with the paradoxical activation of MAPK signaling and leads to accelerated growth of these lesions. (Funded by Hoffmann–La Roche and others; ClinicalTrials.gov numbers, NCT00405587, NCT00949702, NCT01001299, and NCT01006980.)

Fertilization triggers egg activation and converts the egg into a developing embryo. The events of this egg-to-embryo transition typically include the resumption of meiosis, the reorganization of the cortical actin cytoskeleton, and the remodeling of the oocyte surface. The factors that regulate sperm-dependent egg-activation events are not well understood. Caenorhabditis elegans EGG-3, a member of the protein tyrosine phosphatase-like (PTPL) family, is essential for regulating cell-surface and cortex rearrangements during egg activation in response to sperm entry. Although fertilization occurred normally in egg-3 mutants, the polarized dispersal of F-actin is altered, a chitin eggshell is not formed, and no polar bodies are produced. EGG-3 is associated with the oocyte plasma membrane in a pattern that is similar to CHS-1 and MBK-2. CHS-1 is required for eggshell deposition, whereas MBK-2 is required for the degradation of maternal proteins during the egg-to-embryo transition. The localization of CHS-1 and EGG-3 are interdependent and both genes were required for the proper localization of MBK-2 in oocytes. Therefore, EGG-3 plays a central role in egg activation by influencing polarized F-actin dynamics and the localization or activity of molecules that are directly involved in executing the egg-to-embryo transition.

Summary The molecular underpinnings of the oocyte-to-embryo transition are poorly understood. Here we show that two protein tyrosine phosphatase-like (PTPL) family proteins, EGG-4 and EGG-5, are required for key events of the oocyte-to-embryo transition in Caenorhabditis elegans. The predicted EGG-4 and EGG-5 amino acid sequences are 99% identical and their functions are redundant. In embryos lacking EGG-4 and EGG-5 we observe defects in meiosis, polar body formation, the block to polyspermy, F-actin dynamics, and eggshell deposition. During oogenesis, EGG-4 and EGG-5 assemble at the oocyte cortex with the previously identified regulators or effectors of the oocyte-to-embryo transition EGG-3, CHS-1 and MBK-2 [1, 2]. All of these molecules share a complex interdependence with regards to their dynamics and subcellular localization. Shortly after fertilization, EGG-4 and EGG-5 are required to properly coordinate a redistribution of CHS-1 and EGG-3 away from the cortex during meiotic anaphase I. Therefore EGG-4 and EGG-5 are not only required for critical events of the oocyte-to-embryo transition but also link the dynamics of the regulatory machinery with the advancing cell cycle.

Fertilization involves multiple layers of sperm-egg interactions that lead to gamete fusion and egg activation. There must be specific molecules required for these interactions. The challenge is to determine the identity of the genes encoding these molecules and how their protein products function. The nematode worm Caenorhabditis elegans has emerged as an efficient model system for gene discovery and understanding the molecular mechanisms of fertilization. The primary advantage of the C. elegans system is the ability to isolate and maintain mutants that affect sperm or eggs and no other cells. In this review we describe progress and challenges in the analysis of genes required for gamete interactions and egg activation in the worm.

CRTH2 is one of the prostaglandin D₂ receptors and plays a proinflammatory role in allergic diseases. Gene expression markers in whole blood induced by CRTH2 activation have not previously been reported. Using microarray analyses of 54 675 genes, we revealed modest gene expression changes in human whole blood stimulated in vitro by a selective CRTH2 agonist, DK-PGD₂. Five genes were found to exhibit 1.5- to 2.6-fold changes in expression. The expression of Charcot-Leyden crystal protein/galectin-10 (CLC/Gal-10) in particular was consistently enhanced in human whole blood stimulated by DK-PGD₂, as confirmed by quantitative real-time polymerase chain reaction analyses. DK-PGD(2)-induced increases in blood CLC/Gal-10 mRNA levels were largely attenuated by the CRTH2 antagonist CAY10471.Thus, the DK-PGD₂-induced CLC/Gal-10 mRNA level can serve as a potential marker for monitoring pharmacodynamic effects of blood exposure to CRTH2 modulating agents.

OBJECTIVES: Folate receptor alpha (FolRα) is a cell-surface glycoprotein, highly expressed in ovarian and endometrial adenocarcinoma, and thus a promising target for cancer therapy using antibody drug conjugates (ADCs). Most ADCs currently in development are generated by random attachment of the cytotoxic payload to the antibody and result in a heterogeneous mixture, comprised of many different forms that are likely to vary in stability and activity, and therefore may be suboptimal therapeutic agents. We have employed an E. coli cell-free expression system (XpressCFTM) and site-specific conjugation technology, to generate STRO-002, a novel homogenous FolRα-targeting ADC. STRO-002 was optimized by selection of the antibody, drug-linker, conjugation site and drug-antibody ratio (DAR) that conferred the best pharmacological properties. We have conducted preclinical studies to evaluate the stability of STRO-002 and characterize the pharmacological properties of the cytotoxic metabolite SC209. In vitro cytotoxicity assays and in vivo efficacy studies were conducted to evaluate the activity of STRO-002 in multiple ovarian cancer cell lines and xenografts. IND enabling toxicology studies were conducted to determine the safety profiles for STRO-002 and its metabolite SC209 in cynomolgous monkeys and rats, respectively. RESULTS: Based on optimization studies, the anti-FolRα human IgG1 antibody (H01/SP8166) conjugated to a proprietary cleavable drug-linker (SC239) was selected for the lead ADC STRO-002. SC239 contains a tubulin-targeting 3-aminophenyl hemiasterlin warhead, SC209, which has potent cytotoxic activity. Based on most favorable anti-tumor activity, positions 180 and 404 on each heavy chain were selected for conjugation of SC239 to SP8166 to yield an ADC with DAR of ~ 4. The drug-linkage in STRO-002 is highly stable and the released warhead, SC209, is a very weak substrate for cellular drug-resistance efflux pumps and is cleared rapidly from plasma. STRO-002 has potent but highly specific cytotoxic activity (0.1-3 nM) on multiple FolRα-positive ovarian cancer cell lines in vitro and anti-tumor efficacy in ovarian xenograft models. STRO-002 exhibits dose-dependent tumor growth inhibition in Igrov-1 tumor xenografts at a single dose and complete regression is achieved in Igrov-1 and OVCAR-3 tumors with a single dose at 10 and 5 mg/kg, respectively. In addition, administration of STRO-002 in combination with carboplatin confers added benefit in efficacy in Igrov-1 tumors. Toxicology studies show favorable safety profiles for STRO-002 and SC209. The main toxicity finding in monkeys dosed up to 9 mg/kg consists of reversible hematopoietic/lymphoid tissue toxicity, which is considered antigen-independent and is consistent with the anti-proliferative effects of SC209 observed in single-dose toxicology studies in rats. No evidence of ocular toxicity due to SC209 were observed in either species. CONCLUSIONS: STRO-002 is a highly specific FolRα targeting ADC with minimal drug moiety release in circulation and the potential for an improved safety and activity profile, and a reduced risk of tumor drug resistance. Our data supports the advancement of STRO-002 to the clinic as a potential treatment of FolRα expressing malignancies such as ovarian cancer. Citation Format: Cristina Abrahams, Stellanie Krimm, Xiaofan Li, Sihong Zhou, Jeffrey Hanson, Mary Rose Masikat, Krishna Bajjuri, Tyler Heibeck, Dharti Kothari, Abigail Yu, Robert Henningsen, Cuong Tran, Gang Yin, James Zawada, Julie Hang, Maureen Bruhns, Willy Solis, Alexander Steiner, Adam Galan, Toni Kline, Ryan Stafford, Alice Yam, Venita I. De Almeida, Mark Lupher, Jr., Trevor Hallam. PRECLINICAL ACTIVITY AND SAFETY OF STRO-002, A NOVEL ADC TARGETING FOLATE RECEPTOR ALPHA FOR OVARIAN AND ENDOMETRIAL CANCER [abstract]. In: Proceedings of the 12th Biennial Ovarian Cancer Research Symposium; Sep 13-15, 2018; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2019;25(22 Suppl):Abstract nr NT-090.

Meiotic maturation and ovulation rates in Caenorhabditis elegans are regulated by a sperm-released gradient of major sperm protein (MSP). Recent work has provided insights into the modulation of the MSP signal by the trafficking of its receptor in oocytes.

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