Marine ecosystems contain over 80% of the world’s biodiversity, and many of these organisms have evolved unique adaptations enabling survival in diverse and challenging environments. The biodiversity within the world’s oceans is a virtually untapped resource for the isolation and development of novel compounds, treatments, and solutions to combat human disease. In particular, while over half of our anti-cancer drugs are derived from natural sources, almost all of these are from terrestrial ecosystems. Yet, even from the limited analyses to date, a number of marine-derived anti-cancer compounds have been approved for clinical use, and several others are currently in clinical trials. Here, we review the current suite of marine-derived anti-cancer drugs, with a focus on how these compounds act upon the hallmarks of cancer. We highlight potential marine environments and species that could yield compounds with unique mechanisms. Continued exploration of marine environments, along with the characterization and screening of their inhabitants for unique bioactive chemicals, could prove fruitful in the hunt for novel anti-cancer therapies.

Colorectal cancer (CRC) is the third most prevalent form of cancer in the United States and results in over 50,000 deaths per year. Treatments for metastatic CRC are limited, and therefore there is an unmet clinical need for more effective therapies. In our prior work, we coupled high-throughput chemical screens with patient-derived models of cancer to identify new potential therapeutic targets for CRC. However, this pipeline is limited by (1) the use of cell lines that do not appropriately recapitulate the tumor microenvironment, and (2) the use of patient-derived xenografts (PDXs), which are time-consuming and costly for validation of drug efficacy. To overcome these limitations, we have turned to patient-derived organoids. Organoids are increasingly being accepted as a “standard” preclinical model that recapitulates tumor microenvironment cross-talk in a rapid, cost-effective platform. In the present work, we employed a library of natural products, intermediates, and drug-like compounds for which full synthesis has been demonstrated. Using this compound library, we performed a high-throughput screen on multiple low-passage cancer cell lines to identify potential treatments. The top candidate, psymberin, was further validated, with a focus on CRC cell lines and organoids. Mechanistic and genomics analyses pinpointed protein translation inhibition as a mechanism of action of psymberin. These findings suggest the potential of psymberin as a novel therapy for the treatment of CRC.

3592 Background: Patient-derived models of cancer, such as cell lines, patient-derived organoids, and patient-derived xenografts, are useful models of patient response in the clinic. However, these models are often not clinically applicable within the time periods necessary to inform clinical decision making, as they can take weeks to months to develop. An ideal platform using patient-derived models would be generated from a core biopsy with a subsequent drug screen within 10-14 days to minimize delay in therapy. We recently reported the development of MicroOrganoSpheres (MOS) that can be used in drug screens within 14 days of obtaining a biopsy. In the current study, we use this MOS system as precision oncology platform in colorectal cancer (CRC) to identify new therapies and predict response to therapy. Methods: CRC patient tissue samples were collected under a Duke Institutional Review Board approved protocol (Pro00089222). Resections or biopsies were mechanically and enzymatically digested to obtain a single cell suspension. Cells were then plated in Matrigel at a ratio of 20,000 cells:5 µL Matrigel to establish “mini-bulk” organoid cultures. After establishment for 5-7 days, cultures were harvested with subsequent generation of MOS at a ratio of 50 cells per MOS. After growing for 3-4 days, MOS were used for dose-response curves using oxaliplatin, SN38, and 5-Fluorouracil (5-FU) as well as high-throughput drug screens with the NCI Approved Oncology Drugs Set VI library. Results: We developed and optimized a MOS pipeline on over 50 CRC specimens, including 9 primary rectal, 35 primary CRC, 12 CRC liver metastasis, and 1 CRC lung metastasis lines with a success rate of 80% and an average of 10-21days from biopsy to MOS generation. The high success of generating CRC MOS in a clinically applicable time frame led to the next phase of the project where a total of 10 CRC MOS were tested against standard of care chemotherapy agents used in CRC (oxaliplatin, irinotecan and 5-FU) as well as the NCI Approved Oncology Drugs Set VI within 14-21days of establishment. We noted a range of sensitivity of approximately 100-fold for standard of care agents. The most sensitive drugs found in the high-throughput screen were Bortezomib, Carfilzomib, and Panobinostat and the most resistant were Gefitinib, Chlorambucil, and Procarbazine hydrochloride. Conclusions: These results demonstrate that our MOS pipeline can be used as a precision oncology platform within a clinically applicable time frame to potentially guide therapy. We are now in the process of correlating drug response in MOS to patient outcome data and these findings will be presented at the annual meeting.

Triple-negative breast cancer (TNBC), defined by the lack of expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER-2), is the most aggressive and lethal form of breast cancer. The treatment of chemo-resistant TNBC tumors is particularly challenging due to the overexpression of efflux transporters, increased DNA repair, and the occurrence of genetic mutations that decrease the likelihood of apoptosis. Lack of clear targets and development of drug resistance allows TNBC to advance to metastatic stage thus resulting in poor prognosis and survival outcome. Recently, we discovered thieno-pyrimidin-hydrazinyl (TPH) class of small molecules that causes necroptotic (i.e. programmed necrosis) cell death in TNBC cells. We found that the lead compound TPH104 has an IC50 value of 160-400 nm and has ~400-fold selectivity towards different TNBC cell lines compared to normal breast cells. TPH104 selectively induced receptor interacting protein kinase 1 (RIPK1) - mediated necroptosis, while promoting autophagy thus resulting in significant inhibition of TNBC cell proliferation. We characterized eighteen novel TPH analogs for their cytotoxic potential and structure activity relation (SAR) and learned that the subtle changes in TPH pharmacophore could enhance or decrease efficacy against TNBC cells. We observed that 2-OH group is required to exert cytotoxic potency. Two new hit analogs of TPH104, TPH104c and TPH104m were found to activate necroptotic cell death markers (RIP, MLKL) with IC50 values similar to TPH104 in TNBC cells. Both analogs decreased the TNBC cell proliferation, and rate of colony formation compared to controls. Mechanistically, similar to TPH104, these analogs did not produce significant apoptosis induction i.e. no loss of mitochondrial membrane potential and arrested the TNBC cells in S-phase of cell cycle. Interestingly, unlike TPH104, TPH104c and TPH104m activate executioner caspases 3 and 7 only at extremely high concentration. TPH104 and its analogs reversed resistance mediated by ABCB1 and ABCG2 transporters through collateral sensitivity. TPH analogs in combination with doxorubicin and paclitaxel synergistically inhibited TNBC and TNBC/resistant (R) cells and reduced the dose-reduction index. Further understanding SAR of TPH analogs and the biology of non-apoptotic, necroptosis cell death by this new class of small molecules will help define a multimodal, non-apoptotic approach to overcome chemoresistance in TNBC patients. This will lead to the development of more selective and efficacious compounds that kills TNBC cells through unique cell death mechanism. Citation Format: Saloni Malla, Diwakar Bastihalli Tukaramrao, Divya L. Dayanidhi, Pia Vogel, Shikha Kumari, Amit K. Tiwari. Necroptosis inducing thienopyridine analogs overcomes chemoresistance in TNBC [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4119.