Cancer cell fusion: a potential target to tackle drug-resistant and metastatic cancer cells

Biosensors for metastatic cancer cell detection

Early detection and effective cancer treatment are critical to improving metastatic cancer cell diagnosis and management today. In particular, accurate qualitative diagnosis of metastatic cancer cell represents an important step in the diagnosis of cancer. Today, biosensors have been widely developed due to the daily need to measure different chemical and biological species. Biosensors are utilized to quantify chemical and biological phenomena by generating signals that are directly proportional to the quantity of the analyte present in the reaction. Biosensors are widely used in disease control, drug delivery, infection detection, detection of pathogenic microorganisms, and markers that indicate a specific disease in the body. These devices have been especially popular in the field of metastatic cancer cell diagnosis and treatment due to their portability, high sensitivity, high specificity, ease of use and short response time. This article examines biosensors for metastatic cancer cells. It also studies metastatic cancer cells and the mechanism of metastasis. Finally, the function of biosensors and biomarkers in metastatic cancer cells is investigated.

Discovery of New Anti-Cancer Agents against Patient-Derived Sorafenib-Resistant Papillary Thyroid Cancer

Thyroid cancer is the most well-known type of endocrine cancer that is easily treatable and can be completely cured in most cases. Nonetheless, anti-cancer drug-resistant metastasis or recurrence may occur and lead to the failure of cancer therapy, which eventually leads to the death of a patient with cancer. This study aimed to detect novel thyroid cancer target candidates based on validating and identifying one of many anti-cancer drug-resistant targets in patient-derived sorafenib-resistant papillary thyroid cancer (PTC). We focused on targeting the sarco/endoplasmic reticulum calcium ATPase (SERCA) in patient-derived sorafenib-resistant PTC cells compared with patient-derived sorafenib-sensitive PTC cells. We discovered novel SERCA inhibitors (candidates 33 and 36) by virtual screening. These candidates are novel SERCA inhibitors that lead to remarkable tumor shrinkage in a xenograft tumor model of sorafenib-resistant patient-derived PTC cells. These results are clinically valuable for the progression of novel combinatorial strategies that facultatively and efficiently target extremely malignant cancer cells, such as anti-cancer drug-resistant PTC cells.

A Multifunctional Delivery System for Remodulating Cell Behaviors of Circulating Malignant Cells to Prevent Cell Fusion

Cell fusion plays a critical role in cancer progression and metastasis. However, effective modulation of the cell fusion behavior and timely evaluation on the cell fusion to provide accurate information for personalized therapy are facing challenges. Here, it demonstrates that the cancer cell fusion behavior can be efficiently modulated and precisely detected through employing a multifunctional delivery vector to realize cancer targeting delivery of a genome editing plasmid and a molecular beacon-based AND logic gate. The multifunctional delivery vector decorated by AS1411 conjugated hyaluronic acid and NLS-GE11 peptide conjugated hyaluronic acid can specifically target circulating malignant cells (CMCs) of cancer patients to deliver the genome editing plasmid for epidermal growth factor receptor (EGFR) knockout. The cell fusion between CMCs and endothelial cells can be detected by the AND logic gate delivered by the multifunctional vector. After EGFR knockout, the edited CMCs exhibit dramatically inhibited cell fusion capability, while unedited CMCs can easily fuse with human umbilical vein endothelial cells (HUVEC) to form hybrid cells. This study provides a new therapeutic strategy for preventing cancer progression and a reliable tool for evaluating cancer cell fusion for precise personalized therapy.

Myeloid-like tumor hybrid cells in bone marrow promote progression of prostate cancer bone metastasis

BACKGROUND

Bone metastasis is the leading cause of death in patients with prostate cancer (PCa) and currently has no effective treatment. Disseminated tumor cells in bone marrow often obtain new characteristics to cause therapy resistance and tumor recurrence. Thus, understanding the status of disseminated prostate cancer cells in bone marrow is crucial for developing a new treatment.

METHODS

We analyzed the transcriptome of disseminated tumor cells from a single cell RNA-sequencing data of PCa bone metastases. We built a bone metastasis model through caudal artery injection of tumor cells, and sorted the tumor hybrid cells by flow cytometry. We performed multi-omics analysis, including transcriptomic, proteomic and phosphoproteomic analysis, to compare the difference between the tumor hybrid cells and parental cells. In vivo experiments were performed to analyze the tumor growth rate, metastatic and tumorigenic potential, drug and radiation sensitivity in hybrid cells. Single cell RNA-sequencing and CyTOF were performed to analyze the impact of hybrid cells on tumor microenvironment.

RESULTS

Here, we identified a unique cluster of cancer cells in PCa bone metastases, which expressed myeloid cell markers and showed a significant change in pathways related to immune regulation and tumor progression. We found that cell fusion between disseminated tumor cells and bone marrow cells can be source of these myeloid-like tumor cells. Multi-omics showed the pathways related to cell adhesion and proliferation, such as focal adhesion, tight junction, DNA replication, and cell cycle, were most significantly changed in these hybrid cells. In vivo experiment showed hybrid cells had a significantly increased proliferative rate, and metastatic potential. Single cell RNA-sequencing and CyTOF showed tumor-associated neutrophils/monocytes/macrophages were highly enriched in hybrid cells-induced tumor microenvironment with a higher immunosuppressive capacity. Otherwise, the hybrid cells showed an enhanced EMT phenotype with higher tumorigenicity, and were resistant to docetaxel and ferroptosis, but sensitive to radiotherapy.

CONCLUSION

Taken together, our data demonstrate that spontaneous cell fusion in bone marrow can generate myeloid-like tumor hybrid cells that promote the progression of bone metastasis, and these unique population of disseminated tumor cells can provide a potential therapeutic target for PCa bone metastasis.

Anti-Cancer SERCA Inhibitors Targeting Sorafenib-Resistant Human Papillary Thyroid Carcinoma

Thyroid cancer is generally curable and, in many cases, can be completely treated, although it can sometimes recur after cancer therapy. Papillary thyroid cancer (PTC) is known as one of the most general subtypes of thyroid cancer, which take up nearly 80% of whole thyroid cancer. However, PTC may develop anti-cancer drug resistance via metastasis or recurrence, making it practically incurable. In this study, we propose a clinical approach that identifies novel candidates based on target identification and validation of numerous survival-involved genes in human sorafenib-sensitive and -resistant PTC. Consequently, we recognized a sarco/endoplasmic reticulum calcium ATPase (SERCA) in human sorafenib-resistant PTC cells. Based on the present results, we detected novel SERCA inhibitor candidates 24 and 31 via virtual screening. These SERCA inhibitors showed remarkable tumor shrinkage in the sorafenib-resistant human PTC xenograft tumor model. These consequences would be clinically worthwhile for the development of a new combinatorial strategy that effectively targets incredibly refractory cancer cells, such as cancer stem cells and anti-cancer drug-resistant cells.

Multi-Targeting Nano-Systems Targeting Heterogeneous Cancer Cells for Therapeutics and Biomarker Detection

Cancer heterogeneity plays a vital part in cancer resistance and metastasis. To provide a reliable approach to exert a therapy action and evaluate its efficiency in heterogeneous cancer cells, a multiple targeting delivery vector composed of histone encapsulating the therapeutic or diagnostic agent, hyaluronic acid targeting CD44 overexpressed in stem tumor cells, SYL3C aptamer targeting epithelial cell adhesion molecule (EpCAM) overexpressed in epithelial cancer cells, and CL4 aptamer targeting epidermal growth factor receptor (EGFR) overexpressed in mesenchymal cancer cells, is developed. The vector can efficiently target different cancer cells and circulating tumor cells (CTCs) in the peripheral blood of patients for mucin 1 (MUC1) knockout. Furthermore, the multiple targeting vector can be used to co-encapsulate three types of molecular beacons for probing various mRNA biomarkers at single-cell resolution after genome editing. This study provides an efficient approach for exerting therapeutic actions in heterogeneous cancer cells and assessing the therapeutic efficacy by detection of cancer biomarkers via liquid biopsy.

Knockdown of PROM2 Enhances Paclitaxel Sensitivity in Endometrial Cancer Cells by Regulating the AKT/FOXO1 Pathway

BACKGROUND

Endometrial cancer is a very common and highly lethal reproductive malignant tumour in women. Paclitaxel (PTX) is a usual drug utilized in chemotherapy for endometrial cancer. It has been uncovered that PROM2 participates in the progression of various cancers through playing a promoter. However, the regulatory function of PROM2 in PTX treatment for endometrial cancer remains unclear.

METHODS

The cell viability (IC50) was examined through CCK8 assay. The mRNA and protein expressions of genes were measured through RT-qPCR and western blot. The proliferation was evaluated through colony formation and EdU assays. The cell apoptosis was assessed through flow cytometry.

RESULTS

In this work, through bioinformatic analysis on online websites, it is found that the up-regulated expression of PROM2 existed in endometrial cancer. In addition, the survival probability of UCEC patients with high PROM2 expression was worse. This study adopted PTX treatment for obtaining the PTX-resistant cells (HEC-1A/PTX and KLE/PTX). Furthermore, suppression of PROM2 enhanced PTX sensitivity through decreasing IC50 and proliferation in endometrial cancer. Additionally, knockdown of PROM2 facilitated cell apoptosis in HEC-1A/PTX and KLE/PTX cells. Next, we found that silencing of PROM2 retards the AKT/FOXO1 pathway. At last, rescue assays reversed the strengthened PTX sensitivity mediated by PROM2 inhibition after SC79 treatment (AKT activator).

CONCLUSION

Knockdown of PROM2 enhanced PTX sensitivity in endometrial cancer through modulating the AKT/FOXO1 pathway. This study hinted that PROM2 may be a useful therapeutic target for PTX treatment in endometrial cancer.

Precise Detection on Cell-Cell Fusion by a Facile Molecular Beacon-Based Method

Cell-cell fusion studies provide an experimental platform for evaluating disease progression and investigating cell infection. However, to realize sensitive and quantitative detection on cell-cell fusion is still a challenge. Herein, we report a facile molecular beacon (MB)-based method for precise detection on cell-cell fusion. By transfection of the spike protein (S protein) and enhanced green fluorescent protein (EGFP) in HEK 293 cells, the virus-mimicking fusogenic effector cells 293-S-EGFP cells were constructed to interact with target cells. Before mixing the effector cells with the target cells, the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) expression in 293-S-EGFP cells was silenced, and the MB for GAPDH mRNA detection was delivered into the GAPDH silenced 293-S-EGFP cells. Once cell-cell fusion occurred, MB migrated from the GAPDH silenced effector cells to the target cells and hybridized with GAPDH mRNA in the target cells to induce fluorescence emission. The cell-cell fusion can be easily visualized and quantitated by fluorescence microscopy and flow cytometry. The fluorescence intensity is strongly dependent on the number of fused target cells. This MB-based method can easily identify the differences in the cell fusions for various target cells with different angiotensin-converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) expression levels, resulting in dramatically different fluorescence intensities in fused target cells. Our study provides a convenient and efficient quantitative detection approach to study cell-cell fusion.

Lipid-mediated ex vivo cell surface engineering for augmented cellular functionalities

Once administrated, intercellular adhesion to recognize and/or arrest target cells is essential for specific treatments, especially for cancer or tumor. However, immune cells administrated into the tumor-microenvironment could lose their intrinsic functionalities such as target recognition ability, resulting in an ineffective cancer immunotherapy. Various manipulation techniques for decorating functional moieties onto cell surface and enhancing target recognition have been developed. A hydrophobic interaction-mediated ex-vivo cell surface engineering using lipid-based biomaterials could be a state-of-the-art engineering technique that could achieve high-efficiency cell surface modification by a single method without disturbance of intrinsic characteristics of cells. In this regard, this review provides design principles for the development of lipid-based biomaterials with a linear structure of lipid, polyethylene glycol, and functional group, strategies for the synthesis process, and their practical applications in biomedical engineering. Especially, we provide new insights into the development of a novel surface coating techniques for natural killer (NK) cells with engineering decoration of cancer targeting moieties on their cell surfaces. Among immune cells, NK cells are interesting cell population for substituting T cells because of their excellent safety and independent anticancer efficacy. Thus, optimal strategies to select cancer-type-specific targeting moieties and present them onto the surface of immune cells (especially, NK cells) using lipid-based biomaterials could provide additional tools to capture cancer cells for developing novel immune cell therapy products. Enhanced anticancer efficacies by surface-engineered NK cells have been demonstrated both in vitro and in vivo. Therefore, it could be speculated that recent progresses in cell surface modification technology via lipid-based biomaterials could strengthen immune surveillance and immune synapses for utilization in a next-generation cancer immunotherapy, beyond currently available genetic engineering tool such as chimeric antigen receptor-mediated immune cell modulation.

Drug Discovery Using Evolutionary Similarities in Chemical Binding to Inhibit Patient-Derived Hepatocellular Carcinoma

Drug resistance causes therapeutic failure in refractory cancer. Cancer drug resistance stems from various factors, such as patient heterogeneity and genetic alterations in somatic cancer cells, including those from identical tissues. Generally, resistance is intrinsic for cancers; however, cancer resistance becomes common owing to an increased drug treatment. Unfortunately, overcoming this issue is not yet possible. The present study aimed to evaluate a clinical approach using candidate compounds 19 and 23, which are sarcoplasmic/endoplasmic reticulum calcium ATPase (SERCA) inhibitors, discovered using the evolutionary chemical binding similarity method. mRNA sequencing indicated SERCA as the dominant marker of patient-derived anti-cancer drug-resistant hepatocellular carcinoma (HCC), but not of patient-derived anti-cancer drug-sensitive HCC. Candidate compounds 19 and 23 led to significant tumor shrinkage in a tumor xenograft model of anti-cancer drug-resistant patient-derived HCC cells. Our results might be clinically significant for the development of novel combinatorial strategies that selectively and efficiently target highly malignant cells such as drug-resistant and cancer stem-like cells.

Colorectal Cancer Stem Cells Fuse with Monocytes to Form Tumour Hybrid Cells with the Ability to Migrate and Evade the Immune System

Simple Summary

Colorectal cancer survival rates strongly decrease from initial to more advanced stages, primarily because of the occurrence of metastatic lesions. In this line, the search for clinical markers is of critical need. The aim of our study was to examine in vitro generated colorectal tumour hybrid cells (THCs) as a fusion between colorectal cancer (CRC) stem cells and human monocytes, as well as to evaluate their presence in tissue and blood samples from CRC patients. THCs, defined as CD45⁺CD14⁺EpCAM⁺, showed enhanced migratory, proliferative and immune evasion abilities compared to their parental cells. In a retrospective cohort of 23 patients, our data showed the potential relevance of resident tissue THCs in the generation of distant metastases. In addition, in a prospective cohort of 38 patients, our data confirmed the correlation between circulating THCs and sSIGLEC5 levels, a molecule which has already been previously described as a marker of poor prognosis in CRC patients. Altogether, our findings indicate that the number of THCs could serve as a novel biomarker for metastasis prediction in colorectal cancer patients.

Abstract

Background: The cancer cell fusion theory could be one of the best explanations for the metastasis from primary tumours. Methods: Herein, we co-cultured colorectal cancer (CRC) stem cells with human monocytes and analysed the properties of the generated tumour hybrid cells (THCs). The presence of THCs in the bloodstream together with samples from primary and metastatic lesions and their clinical correlations were evaluated in CRC patients and were detected by both FACS and immunofluorescence methods. Additionally, the role of SIGLEC5 as an immune evasion molecule in colorectal cancer was evaluated. Results: Our data demonstrated the generation of THCs after the in vitro co-culture of CRC stem cells and monocytes. These cells, defined as CD45⁺CD14⁺EpCAM⁺, showed enhanced migratory and proliferative abilities. The THC-specific cell surface signature allows identification in matched primary tumour tissues and metastases as well as in the bloodstream from patients with CRC, thus functioning as a biomarker. Moreover, SIG-LEC5 expression on in vitro generated THCs has shown to be involved in the mechanism for immune evasion. Additionally, sSIGLEC5 levels correlated with THC numbers in the prospective cohort of patients. Conclusions: Our results indicate the generation of a hybrid entity after the in vitro co-culture between CRC stem cells and human monocytes. Moreover, THC numbers present in patients are related to both prognosis and the later spread of metastases in CRC patients.

Multinucleated Giant Cells: Current Insights in Phenotype, Biological Activities, and Mechanism of Formation

Monocytes and macrophages are innate immune cells with diverse functions ranging from phagocytosis of microorganisms to forming a bridge with the adaptive immune system. A lesser-known attribute of macrophages is their ability to fuse with each other to form multinucleated giant cells. Based on their morphology and functional characteristics, there are in general three types of multinucleated giant cells including osteoclasts, foreign body giant cells and Langhans giant cells. Osteoclasts are bone resorbing cells and under physiological conditions they participate in bone remodeling. However, under pathological conditions such as rheumatoid arthritis and osteoporosis, osteoclasts are responsible for bone destruction and bone loss. Foreign body giant cells and Langhans giant cells appear only under pathological conditions. While foreign body giant cells are found in immune reactions against foreign material, including implants, Langhans giant cells are associated with granulomas in infectious and non-infectious diseases. The functionality and fusion mechanism of osteoclasts are being elucidated, however, our knowledge on the functions of foreign body giant cells and Langhans giant cells is limited. In this review, we describe and compare the phenotypic aspects, biological and functional activities of the three types of multinucleated giant cells. Furthermore, we provide an overview of the multinucleation process and highlight key molecules in the different phases of macrophage fusion.

Hybrid/Atypical Forms of Circulating Tumor Cells: Current State of the Art

Cancer is one of the most common diseases worldwide, and its treatment is associated with many challenges such as drug and radioresistance and formation of metastases. These difficulties are due to tumor heterogeneity, which has many causes. One may be the cell fusion, a process that is relevant to both physiological (e.g., wound healing) and pathophysiological (cancer and viral infection) processes. This literature review aimed to summarize the existing data on the hybrid/atypical forms of circulating cancer cells and their role in tumor progression. For that, the bioinformatics search in universal databases, such as PubMed, NCBI, and Google Scholar was conducted by using the keywords “hybrid cancer cells”, “cancer cell fusion”, etc. In this review the latest information related to the hybrid tumor cells, theories of their genesis, characteristics of different variants with data from our own researches are presented. Many aspects of the hybrid cell research are still in their infancy. However, with the level of knowledge already accumulated, circulating hybrids such as CAML and CHC could be considered as promising biomarkers of cancerous tumors, and even more as a new approach to cancer treatment.

Keep Calm and Carry on with Extra Centrosomes

Simple Summary

Precise chromosome segregation during mitosis is a vital event orchestrated by formation of bipolar spindle poles. Supernumerary centrosomes, caused by centrosome amplification, deteriorates mitotic processes, resulting in segregation defects leading to chromosomal instability (CIN). Centrosome amplification is frequently observed in various types of cancer and considered as a significant contributor to destabilization of chromosomes. This review provides a comprehensive overview of causes and consequences of centrosome amplification thoroughly describing molecular mechanisms.

Abstract

Aberrations in the centrosome number and structure can readily be detected at all stages of tumor progression and are considered hallmarks of cancer. Centrosome anomalies are closely linked to chromosome instability and, therefore, are proposed to be one of the driving events of tumor formation and progression. This concept, first posited by Boveri over 100 years ago, has been an area of interest to cancer researchers. We have now begun to understand the processes by which these numerical and structural anomalies may lead to cancer, and vice-versa: how key events that occur during carcinogenesis could lead to amplification of centrosomes. Despite the proliferative advantages that having extra centrosomes may confer, their presence can also lead to loss of essential genetic material as a result of segregational errors and cancer cells must deal with these deadly consequences. Here, we review recent advances in the current literature describing the mechanisms by which cancer cells amplify their centrosomes and the methods they employ to tolerate the presence of these anomalies, focusing particularly on centrosomal clustering.

Self-assembled ternary hybrid nanodrugs for overcoming tumor resistance and metastasis

Traditional chemotherapy exhibits a certain therapeutic effect toward malignant cancer, but easily induce tumor multidrug resistance (MDR), thereby resulting in the progress of tumor recurrence or metastasis. In this work, we deigned ternary hybrid nanodrugs (PEI/DOX@CXB-NPs) to simultaneously combat against tumor MDR and metastasis. In vitro results demonstrate this hybrid nanodrugs could efficiently increase cellular uptake at pH 6.8 by the charge reversal, break lysosomal sequestration by the proton sponge effect and trigger drugs release by intracellular GSH, eventually leading to higher drugs accumulation and cell-killing in drug-sensitive/resistant cells. In vivo evaluation revealed that this nanodrugs could significantly inhibit MDR tumor growth and simultaneously prevent A549 tumor liver/lung metastasis owing to the specifically drugs accumulation. Mechanism studies further verified that hybrid nanodrugs were capable of down-regulating the expression of MDR or metastasis-associated proteins, lead to the enhanced anti-MDR and anti-metastasis effect. As a result, the multiple combination strategy provided an option for effective cancer treatment, which could be potentially extended to other therapeutic agents or further use in clinical test.

Cell fusion enhances energy metabolism of mesenchymal tumor hybrid cells to sustain their proliferation and invasion

BACKGROUND

Cell-to-cell fusion is emerging as a key element of the metastatic process in various cancer types. We recently showed that hybrids made from the spontaneous merging of pre-malignant (IMR90 E6E7, i.e. E6E7) and malignant (IMR90 E6E7 RST, i.e. RST) mesenchymal cells recapitulate the main features of human undifferentiated pleomorphic sarcoma (UPS), with a highly rearranged genome and increased spreading capacities. To better characterize the intrinsic properties of these hybrids, we investigated here their metabolic energy profile compared to their parents.

RESULTS

Our results unveiled that hybrids harbored a Warburg-like metabolism, like their RST counterparts. However, hybrids displayed a much greater metabolic activity, enhancing glycolysis to proliferate. Interestingly, modifying the metabolic environmental conditions through the use of 5-aminoimidazole-4-carbox-amide-1-β-D-ribofuranoside (AICAR), an activator of the 5'-adenosine monophosphate (AMP)-activated protein kinase (AMPK), specifically reduced the growth of hybrids, and also abrogated the invasive capacity of hybrids displaying enhanced glycolysis. Furthermore, AICAR efficiently blocked the tumoral features related to the aggressiveness of human UPS cell lines.

CONCLUSION

Altogether, our findings strongly suggest that hybrids rely on higher energy flux to proliferate and that a drug altering this metabolic equilibrium could impair their survival and be potentially considered as a novel therapeutic strategy.

Tumor-Cell-Macrophage Fusion Cells as Liquid Biomarkers and Tumor Enhancers in Cancer

Although molecular mechanisms driving tumor progression have been extensively studied, the biological nature of the various populations of circulating tumor cells (CTCs) within the blood is still not well understood. Tumor cell fusion with immune cells is a longstanding hypothesis that has caught more attention in recent times. Specifically, fusion of tumor cells with macrophages might lead to the development of metastasis by acquiring features such as genetic and epigenetic heterogeneity, chemotherapeutic resistance, and immune tolerance. In addition to the traditional FDA-approved definition of a CTC (CD45-, EpCAM+, cytokeratins 8+, 18+ or 19+, with a DAPI+ nucleus), an additional circulating cell population has been identified as being potential fusions cells, characterized by distinct, large, polymorphonuclear cancer-associated cells with a dual epithelial and macrophage/myeloid phenotype. Artificial fusion of tumor cells with macrophages leads to migratory, invasive, and metastatic phenotypes. Further studies might investigate whether these have a potential impact on the immune response towards the cancer. In this review, the background, evidence, and potential relevance of tumor cell fusions with macrophages is discussed, along with the potential role of intercellular connections in their formation. Such fusion cells could be a key component in cancer metastasis, and therefore, evolve as a diagnostic and therapeutic target in cancer precision medicine.

Intratumor Heterogeneity and Therapy Resistance: Contributions of Dormancy, Apoptosis Reversal (Anastasis) and Cell Fusion to Disease Recurrence

A major challenge in treating cancer is posed by intratumor heterogeneity, with different sub-populations of cancer cells within the same tumor exhibiting therapy resistance through different biological processes. These include therapy-induced dormancy (durable proliferation arrest through, e.g., polyploidy, multinucleation, or senescence), apoptosis reversal (anastasis), and cell fusion. Unfortunately, such responses are often overlooked or misinterpreted as “death” in commonly used preclinical assays, including the in vitro colony-forming assay and multiwell plate “viability” or “cytotoxicity” assays. Although these assays predominantly determine the ability of a test agent to convert dangerous (proliferating) cancer cells to potentially even more dangerous (dormant) cancer cells, the results are often assumed to reflect loss of cancer cell viability (death). In this article we briefly discuss the dark sides of dormancy, apoptosis, and cell fusion in cancer therapy, and underscore the danger of relying on short-term preclinical assays that generate population-based data averaged over a large number of cells. Unveiling the molecular events that underlie intratumor heterogeneity together with more appropriate experimental design and data interpretation will hopefully lead to clinically relevant strategies for treating recurrent/metastatic disease, which remains a major global health issue despite extensive research over the past half century.