Current status and future outlook for patient-derived cancer models from a rare cancer research perspective

Establishment and characterization of two novel patient-derived cell lines from myxofibrosarcoma: NCC-MFS7-C1 and NCC-MFS8-C1

Myxofibrosarcoma (MFS), an aggressive soft tissue sarcoma, presents a significant challenge because of its high recurrence rate, distal metastasis, and complex genetic background. Although surgical resection is the standard treatment for MFS, the outcomes are unsatisfactory and effective non-surgical treatment strategies, including drug therapy, are urgently warranted. MFS is a rare tumor that requires comprehensive preclinical research to develop promising drug therapies; however, only two MFS cell lines are publicly available worldwide. The present study reports two novel patient-derived MFS cell lines, NCC-MFS7-C1 and NCC-MFS8-C1. These cell lines have been extensively characterized for their genetic profile, proliferation, spheroid-forming capacity, and invasive behavior, confirming that they retain MFS hallmarks. Furthermore, we conducted comprehensive drug screening against these cell lines and six others previously established in our laboratory to identify potential therapeutic candidates for MFS. Among the screened agents, actinomycin D, bortezomib, and romidepsin demonstrated considerable antiproliferative effects that were superior to those of doxorubicin, a standard drug, highlighting their potential as novel drugs. In conclusion, NCC-MFS7-C1 and NCC-MFS8-C1 are valuable research resources that contribute to the understanding of the pathogenesis and development of novel therapies for MFS.

Current status of in vitro models for rare gynaecological cancer research

Gynaecological cancers originate within the female reproductive system and are classified according to the site in the reproductive system where they arise. However, over 50 % of these malignancies are categorized as rare, encompassing 30 distinct histological subtypes, which complicates their diagnosis and treatment. The focus of this review is to give an overview of established in vitro models for the investigation of rare gynaecological cancers, as well as an overview of available online databases that contain detailed descriptions of cell line characteristics. Cell lines represent the main models for the research of carcinogenesis, drug resistance, pharmacodynamics and novel therapy treatment options. Nowadays, classic 2D cell models are increasingly being replaced with 3D cell models, such as spheroids, organoids, and tumoroids because they provide a more accurate representation of numerous tumour characteristics, and their response to therapy differs from the response of adherent cell lines. It is crucial to use the correct cell line model, as rare tumour types can show characteristics that differ from the most common tumour types and can therefore respond unexpectedly to classic treatment. Additionally, some cell lines have been misclassified or misidentified, which could lead to false results. Even though rare gynaecological cancers are rare, this review will demonstrate that there are available options for investigation of such cancers in vitro on biologically relevant models.

A Novel Method for the Early Detection of Single Circulating, Metastatic and Self-Seeding Cancer Cells in Orthotopic Breast Cancer Mouse Models

BACKGROUND

Metastasis is the main cause of cancer-related deaths, but efficient targeted therapies against metastasis are still missing. Major gaps exist in our understanding of the metastatic cascade, as existing methods cannot combine sensitivity, robustness, and practicality to dissect cancer progression. Addressing this issue requires improved strategies to distinguish early metastatic colonization from metastatic outgrowth.

METHODS

Luciferase-labelled MDA-MB-231, MCF7, and 4T1 breast cancer cells were spiked into samples from tumour-naïve mice to establish the limit of detection for disseminated tumour cells. Luciferase-labelled breast cancer cells (±unlabelled cancer-associated fibroblasts; CAFs) were orthotopically implanted in immunocompromised mice. An ex vivo luciferase assay was used to quantify tumour cell dissemination.

RESULTS

In vitro luciferase assay confirmed a linear and positive correlation between cancer cell numbers and the bioluminescence detected at single cell level in blood, brain, lung, liver, and mammary fat pad samples. Remarkably, single luciferase-labelled cancer cells were detectable in all of these sites, as the bioluminescence quantified in the analysed samples was substantially higher than background levels. Ex vivo, circulating tumour cells, metastasis, and tumour self-seeding were detected in all samples from animals implanted with highly metastatic luciferase-labelled MDA-MB-231 cells. In turn, detection of poorly metastatic luciferase-labelled MCF7 cells was scarce but significantly enhanced upon co-implantation with CAFs as early as 20 days after the experiment was initiated.

CONCLUSIONS

These results demonstrate the feasibility of using an ultrasensitive luciferase-based method to dissect the mechanisms of early metastatic colonization to improving the development of antimetastatic therapies.

Establishment and characterization of two novel patient-derived cell lines from giant cell tumor of bone: NCC-GCTB8-C1 and NCC-GCTB9-C1

Giant cell tumor of bone (GCTB) is a rare osteolytic bone tumor consisting of mononuclear stromal cells, macrophages, and osteoclast-like giant cells. Although GCTB predominantly exhibits benign behavior, the tumor carries a significant risk of high local recurrence. Furthermore, GCTB can occasionally undergo malignant transformation and distal metastasis, making it potentially fatal. The standard treatment is complete surgical resection; nonetheless, an optimal treatment strategy for advanced GCTB remains unestablished, necessitating expanded preclinical research to identify appropriate therapeutic options. However, only one GCTB cell line is publicly available from a cell bank for research use worldwide. The present study reports the establishment of two novel cell lines, NCC-GCTB8-C1 and NCC-GCTB9-C1, derived from the primary tumor tissues of two patients with GCTB. Both cell lines maintained the hallmark mutation in the H3-3A gene, which is associated with tumor formation and development in GCTB. Characterization of these cell lines revealed their steady growth, spheroid-formation capability, and invasive traits. Potential therapeutic agents were identified via extensive drug screening of the two cell lines and seven previously established GCTB cell lines. Among the 214 antitumor agents tested, romidepsin, a histone deacetylase inhibitor, and mitoxantrone, a topoisomerase inhibitor, were identified as potential therapeutic agents against GCTB. Conclusively, the establishment of NCC-GCTB8-C1 and NCC-GCTB9-C1 provides novel and crucial resources that are expected to advance GCTB research and potentially revolutionize treatment strategies.

Establishment and characterization of NCC-ASPS2-C1: a novel patient-derived cell line of alveolar soft part sarcoma

Alveolar soft part sarcoma (ASPS) is a rare mesenchymal tumor characterized by rearrangement of the ASPSCR1 and TFE3 genes and a histologically distinctive pseudoalveolar pattern. ASPS progresses slowly, but is prone to late metastasis. As ASPS is refractory to conventional chemotherapy, the only curative treatment is complete surgical resection. The prognosis of advanced and metastatic cases is poor, highlighting the need for preclinical research to develop appropriate treatment options. However, ASPS is extremely rare, accounting for < 1% of all soft tissue sarcomas, and only one patient-derived ASPS cell line is available from public cell banks worldwide for research. This study reports the establishment of a novel ASPS cell line derived from the primary tumor tissue of an ASPS patient, named NCC-ASPS2-C1. This cell line retains the ASPSCR1-TFE3 fusion gene, which is characteristic of ASPS. The characterization of this cell line revealed stable growth, spheroid formation, and invasive properties. By screening a drug library using NCC-ASPS2-C1, we identified several drugs that inhibited the proliferation of ASPS cells. In conclusion, the establishment of NCC-ASPS2-C1 provides a valuable resource for advancing ASPS research and developing novel treatments for this challenging disease.

Synergistic antitumor activity between HER2 antibody-drug conjugate and chemotherapy for treating advanced colorectal cancer

Colorectal cancer (CRC) is the third most common cancer associated with a poor prognosis. Effective targeted therapy alone or in combination for treating advanced CRC remains to be a major clinical challenge. Here, we propose the therapeutic efficacy and molecular mechanism underlying RC48, a FDA-approved anti-HER2 antibody conjugate via a cleavable linker to the microtubule inhibitor monomethyl auristatin E (MMAE), either alone or in combination with gemcitabine (GEM) in various models of HER2-positive advanced CRC. Our findings demonstrated that HER2 was widely expressed and located on the plasma membrane of CRC patient specimens, PDX xenograft tumors and cell lines. It confirmed that RC48 alone significantly targeted and eradicated HER2 positive CRC tumor in these models. Moreover, we screened a panel of FDA-approved first-line chemotherapy drugs in vitro. We found that GEM exhibited stronger antiproliferative activity compared to the other first-line anti-cancer agents. Furthermore, combination therapy of RC48 and GEM significantly showed synergetic antitumor activity in vitro and in vivo. To gain further mechanistic insights into the combination therapy, we performed RNA-seq analysis. The results revealed that combination treatment of RC48 and GEM regulated multiple signaling pathways, such as PI3K-AKT, MAPK, p53, Foxo, apoptosis, cell cycle and cell senescence, etc., to exert its antitumor activity in CRC cells. Collectively, these preclinical findings demonstrated that RC48 alone or combinational therapy exerted promising antitumor activity, and meriting the preclinical framework for combinational therapy of anti-HER2 drug conjugate drug and chemotherapy drugs for HER2-positive patients with advanced CRC.

Challenges and opportunities in rare cancer research in China

Cancer is one of the major public health challenges in China. Rare cancers collectively account for a considerable proportion of all malignancies. The lack of awareness of rare cancers among healthcare professionals and the general public, the typically complex and delayed diagnosis, and limited access to clinical trials are key challenges. Recent years have witnessed an increase in funding for research related to rare cancers in China. In this review, we provide a comprehensive overview of rare cancers and summarize the status of research on rare cancers in China and overseas, including the trends of funding and publications. We also highlight the challenges and perspectives regarding rare cancers in China.

Implementation status of pharmacological studies in the development of orphan drugs

BACKGROUND

The nonclinical as well as clinical development of orphan drugs is difficult, owing to unknown pathophysiology and the absence of animal models. Both, the U.S. Food and Drug Administration (FDA) Guidance and European Medicines Agency (EMA) Guidelines, for orphan drug development describe non-clinical studies, but lack specific information, such as animal species and study design. Against this background, this study aimed to elucidate efficient methods for evaluating nonclinical efficacy based on a review report of orphan drugs approved in Japan.

RESULTS

A total of 184 orphan drugs, including 84 anticancer and 100 non-anticancer drugs, approved in Japan from January 2010 to December 2019 were investigated. Some anticancer drugs progressed to clinical development without distinct efficacy data in nonclinical studies. Patient-derived cells have been used for some drugs due to a lack of established cell lines. Cells used for non-clinical studies were devised for drugs indicated for cancers resistant to prior therapies, tumours with specific amino acid mutations in the target molecules, and solid tumours with specific biomarkers. For some non-anticancer drugs, similar disease animal models and normal animals were used for evaluation, since animal models did not exist. Biomarkers have been used specifically for evaluation in normal animals and as endpoints in some clinical trials.

CONCLUSIONS

It was possible to evaluate drug efficacy by flexibly designing nonclinical studies according to disease characteristics for potentials orphan drugs. These approaches, which are not described in detail in the EMA Guideline or FDA Guidance, may thus lead to approval.

Landscape of Genetic Mutations in Appendiceal Cancers

In appendiceal cancers, the most frequently mutated genes are (i) KRAS, which, when reactivated, restores signal transduction via the RAS-RAF-MEK-ERK signaling pathway and stimulates cell proliferation in the early stages of tumor transformation, and then angiogenesis; (ii) TP53, whose inactivation leads to the inhibition of programmed cell death; (iii) GNAS, which, when reactivated, links the cAMP pathway to the RAS-RAF-MEK-ERK signaling pathway, stimulating cell proliferation and angiogenesis; (iv) SMAD4, exhibiting typical tumor-suppressive activity, blocking the transmission of oncogenic TGFB signals via the SMAD2/SMAD3 heterodimer; and (v) BRAF, which is part of the RAS-RAF-MEK-ERK signaling pathway. Diverse mutations are reported in other genes, which are part of secondary or less critical signaling pathways for tumor progression, but which amplify the phenotypic diversity of appendiceal cancers. In this review, we will present the main genetic mutations involved in appendix tumors and their roles in cell proliferation and survival, and in tumor invasiveness, angiogenesis, and acquired resistance to anti-growth signals.

Vitamin D Modulates the Response of Patient-Derived Metastatic Melanoma Cells to Anticancer Drugs

Melanoma is considered a lethal and treatment-resistant skin cancer with a high risk of recurrence, making it a major clinical challenge. Our earlier studies documented that 1,25(OH)₂D₃ and its low-calcaemic analogues potentiate the effectiveness of dacarbazine and cediranib, a pan-VEGFR inhibitor. In the current study, a set of patient-derived melanoma cultures was established and characterised as a preclinical model of human melanoma. Thus, patient-derived cells were preconditioned with 1,25(OH)₂D₃ and treated with cediranib or vemurafenib, a BRAF inhibitor, depending on the BRAF mutation status of the patients enrolled in the study. 1,25(OH)₂D₃ preconditioning exacerbated the inhibition of patient-derived melanoma cell growth and motility in comparison to monotherapy with cediranib. A significant decrease in mitochondrial respiration parameters, such as non-mitochondrial oxygen consumption, basal respiration and ATP-linked respiration, was observed. It seems that 1,25(OH)₂D₃ preconditioning enhanced cediranib efficacy via the modulation of mitochondrial bioenergetics. Additionally, 1,25(OH)₂D₃ also decreased the viability and mobility of the BRAF+ patient-derived cells treated with vemurafenib. Interestingly, regardless of the strict selection, cancer-derived fibroblasts (CAFs) became the major fraction of cultured cells over time, suggesting that melanoma growth is dependent on CAFs. In conclusion, the results of our study strongly emphasise that the active form of vitamin D, 1,25(OH)₂D₃, might be considered as an adjuvant agent in the treatment of malignant melanoma.

Immunotherapies in rare cancers

Cancer remains a leading cause of death worldwide, placing a significant burden on healthcare systems as well as the global economy. Rare cancers comprise a group of about 200 cancers that individually occur at extremely low frequencies. In the United States (US), their frequency is approximately 15 cases per 100,000 people, and it is even lower in Europe with approximately 6 cases per 100,000 people. However, combined their frequency of occurrence is much higher than any singular cancer. Cancer treatment and management has tremendously improved in the last decade, particularly with the administration of immune-based therapies. The four most prevalent immune-based therapies are (1) the use of immune-checkpoint inhibitors, (2) macrophage therapy, (3) Chimeric Antigen Receptor (CAR) T cell therapy, and (4) neoantigen-based therapies. In our review, we discuss these various aproaches and their implementation in the treatment of a variety of rare cancers. Furthermore, we discuss their limitations and potential strategies to overcome them to enhance the therapeutic efficacy of these approaches. Finally, our article presents the future directions and other additional immune therapies that may be incorporated into the treatment of rare cancers.

Nuclear PTEN's Functions in Suppressing Tumorigenesis: Implications for Rare Cancers

Phosphatase and tensin homolog (PTEN) encodes a tumor-suppressive phosphatase with both lipid and protein phosphatase activity. The tumor-suppressive functions of PTEN are lost through a variety of mechanisms across a wide spectrum of human malignancies, including several rare cancers that affect pediatric and adult populations. Originally discovered and characterized as a negative regulator of the cytoplasmic, pro-oncogenic phosphoinositide-3-kinase (PI3K) pathway, PTEN is also localized to the nucleus where it can exert tumor-suppressive functions in a PI3K pathway-independent manner. Cancers can usurp the tumor-suppressive functions of PTEN to promote oncogenesis by disrupting homeostatic subcellular PTEN localization. The objective of this review is to describe the changes seen in PTEN subcellular localization during tumorigenesis, how PTEN enters the nucleus, and the spectrum of impacts and consequences arising from disrupted PTEN nuclear localization on tumor promotion. This review will highlight the immediate need in understanding not only the cytoplasmic but also the nuclear functions of PTEN to gain more complete insights into how important PTEN is in preventing human cancers.

Establishment and characterization of NCC-SS5-C1: a novel patient-derived cell line of synovial sarcoma

Synovial sarcoma (SS) is a rare and aggressive mesenchymal malignancy driven by a unique chromosomal translocation that generates the expression of the SS18:SSX fusion protein. It occurs at almost any anatomical site and most commonly in young adults. The standard curative treatment for primary SS is a wide surgical resection combined with radiotherapy and/or neoadjuvant chemotherapy. The prognosis of SS varies among patients, with the 5 years survival rate ranging from 50 to 60% in adults and 90% in children. Although patient-derived cell lines are a useful resource for the development of new therapies, only a few are available from public cell banks. Therefore, this study aimed to establish and characterize a novel SS cell line. We successfully established a novel cell line, NCC-SS5-C1, harboring an SS18-SSX1 fusion gene. NCC-SS5-C1 cells demonstrated constant growth and invasion ability. We performed integrative drug screening using eight SS cell lines, including NCC-SS5-C1 cells, and examined the response spectrum of existing anticancer agents. We conclude that NCC-SS5-C1 is a useful resource for studying SS.

Establishment and characterization of a novel patient-derived cell line of dedifferentiated liposarcoma, NCC-DDLPS6-C1

Dedifferentiated liposarcoma (DDLPS) is morphologically characterized by well-differentiated liposarcomas associated with high-grade non-lipogenic sarcoma and molecularly characterized by the coamplification of MDM2 and CDK4(12q14-15). DDLPS is highly aggressive, and effective systemic chemotherapy has not been developed yet. In this study, we established a novel DDLPS cell line, NCC-DDLPS6-C1, as a potential tool for the development of novel therapies. NCC-DDLPS6-C1 cells were established from surgically resected tumor tissues of a patient with DDLPS. Amplification and overexpression of MDM2 and CDK4 were observed in NCC-DDLPS6-C1 cells. NCC-DDLPS6-C1 cells proliferated rapidly, invaded aggressively, and formed spheroids. Moreover, NCC-DDLPS6-C1 cells formed tumors in mice. These observations suggested that the malignant potentials that may reflect the original features of DDLPS were retained in the NCC-DDLPS6-C1. Anticancer drugs that significantly reduced the proliferation of NCC-DDLPS6-C1 cells were identified by drug library screening. Thus, NCC-DDLPS6-C1 may recapitulate the original genotypes and phenotypes, and we conclude that the NCC-DDLPS6-C1 cell line is a useful resource for the study of DDLPS.

Establishment and characterization of NCC-DDLPS5-C1: a novel patient-derived cell line of dedifferentiated liposarcoma

Dedifferentiated liposarcoma (DDLPS) is a highly aggressive subtype of liposarcoma that is morphologically defined as a transition from a well-differentiated lipomatous component to a non-lipogenic one. Curative therapy for DDLPS is complete resection, and the benefits of current systemic chemotherapy remain marginal. Although DDLPS is molecularly characterized by co-amplification of MDM2 and CDK4 (12q14-15) and detailed genomic analyses have been conducted by multiple research groups, the effects of molecular targeted drugs are marginal, and novel therapeutic modalities are required. Although patient-derived cell lines are pivotal for cancer research, no DDLPS cell lines are currently available from public cell repositories. Accordingly, in this study, we established a novel DDLPS cell line, NCC-DDLPS5-C1, using surgically resected tumor tissues from a patient with DDLPS. NCC-DDLPS5-C1 cells exhibited typical gene amplification, overexpression of MDM2 and CDK4, and other DNA copy number alterations. The NCC-DDLPS5-C1 cells were capable of rapid cell proliferation, aggressive invasion, and spheroid formation, but not tumor formation in mice. We reported the utility of NCC-DDLPS5-C1 cells for a drug-response assay to detect anticancer drugs that significantly attenuated cell proliferation. Thus, we concluded that the NCC-DDLPS5-C1 cell line could be a useful resource for the study of DDLPS. Considering the diversity of disease in terms of clinical outcomes, continuous efforts are required to develop more patient-derived cancer models with different clinical and pathological backgrounds.

Patient-Derived Organoids in Precision Medicine: Drug Screening, Organoid-on-a-Chip and Living Organoid Biobank

Organoids are in vitro self-assembling, organ-like, three-dimensional cellular structures that stably retain key characteristics of the respective organs. Organoids can be generated from healthy or pathological tissues derived from patients. Cancer organoid culture platforms have several advantages, including conservation of the cellular composition that captures the heterogeneity and pharmacotypic signatures of the parental tumor. This platform has provided new opportunities to fill the gap between cancer research and clinical outcomes. Clinical trials have been performed using patient-derived organoids (PDO) as a tool for personalized medical decisions to predict patients' responses to therapeutic regimens and potentially improve treatment outcomes. Living organoid biobanks encompassing several cancer types have been established, providing a representative collection of well-characterized models that will facilitate drug development. In this review, we highlight recent developments in the generation of organoid cultures and PDO biobanks, in preclinical drug discovery, and methods to design a functional organoid-on-a-chip combined with microfluidic. In addition, we discuss the advantages as well as limitations of human organoids in patient-specific therapy and highlight possible future directions.

The CAM Model for CIC-DUX4 Sarcoma and Its Potential Use for Precision Medicine

(1) Background: CIC-DUX4 sarcoma is a rare mesenchymal small round cell tumor which belongs to rare cancers that occupy a significant percentage of cancer cases as a whole, despite each being rare. Importantly, each rare cancer type has different features, and thus there is a need to develop a model that mimics the features of each of these cancers. We evaluated the idea that the chicken chorioallantoic membrane assay (CAM), a convenient and versatile animal model, can be established for the CIC-DUX4 sarcoma. (2) Methods: Patient-derived cell lines of CIC-DUX4 were applied. These cells were transplanted onto the CAM membrane and tumor formation was examined by H&E staining, immunohistochemistry and Western blotting. The CAM tumor was transferred onto a fresh CAM and was also used to form organoids. Retention of the fusion gene was examined. (3) Results: H&E staining as well as molecular characterization demonstrated the formation of the CIC-DUX4 tumor on the CAM membrane. Expression of cyclin D2 and ETV4 was identified. The CAM tumor was transferred to a fresh CAM to form the second-generation CAM tumor. In addition, we were successful in forming tumor organoids using the CAM tumor. Retention of the fusion gene CIC-DUX4 in the CAM, second-generation CAM, and in the CAM-derived organoids was confirmed by RT-PCR. (4) Conclusions: The CAM assay provides a promising model for CIC-DUX4 sarcoma.

Establishment and characterization of a novel cell line, NCC-DDLPS2-C1, derived from a patient with dedifferentiated liposarcoma

Dedifferentiated liposarcoma (DDLPS) is a highly aggressive subtype of liposarcoma that is histologically a transition form between an atypical lipomatous tumor/well-differentiated liposarcoma and a non-lipogenic sarcoma. DDLPS is genetically characterized by a complex karyotype with copy number variations and genomic complexity. DDLPS has a poor prognosis, a high local recurrence rate, and refractory behaviors for chemotherapy and radiation, which indicate a requirement for a novel therapeutic strategy for better clinical outcomes. We report here, a novel DDLPS cell line (NCC-DDLPS2-C1) developed from a tumor tissue. NCC-DDLPS2-C1 cells showed an amplified 12q13-15 region and exhibited constant growth, spheroid formation, and invasion. High-throughput drug screening revealed distinct sensitivity between monolayer- and three-dimensional cells. Romidepsin and trabectedin especially showed high anti-proliferative effects in both culture methods of NCC-DDLPS2-C1. Thus, the NCC-DDLPS2-C1 cell line may serve as a useful resource for DDLPS studies.

Current status and future outlook for patient-derived cancer models from a rare cancer research perspective

Rare cancers are a group of approximately 200 malignancies with extremely low incidences and with a wide variety of genotypes and phenotypes. Collectively, they are more common than any single malignancy. However, given the small numbers of individuals diagnosed with rare cancers, it is difficult to design clinical trials with sufficient patient numbers. Therefore, few effective anticancer drugs have been developed, and evidence‐based medicine is not always feasible for rare cancers. Consequently, their clinical outcomes are generally poorer. Cancer research requires adequate models that faithfully recapitulate molecular features and reproduce treatment responses of the original tumors. Such models allow us to focus on more efficacious drugs in the clinical studies. For rare cancers, patient‐derived cancer models are particularly important because the enrollment of sufficient patients is rarely attainable within a reasonable period of time. However, extremely few models are available for rare cancers. For example, cell lines and xenografts are available for only a limited number of histological subtypes of sarcomas; therefore, most sarcoma research is performed without such models, and a lack of adequate cancer models causes a lag in therapeutic development. The establishment of novel rare cancer models will dramatically facilitate rare cancer research and treatment development in the near future. This review focuses on the status of patient‐derived rare cancer models and discusses their pivotal problems and possibilities, using sarcomas as a representative rare cancer type. Multi‐institutional collaboration will help address the scarcity of patient‐derived rare cancer models.