MATHEMATICAL MODELING AND BIFURCATION ANALYSIS FOR A BIOLOGICAL MECHANISM OF CANCER DRUG RESISTANCE

Drug resistance is one of the most intractable issues in targeted therapy for cancer diseases.It has also been demonstrated to be related to cancer heterogeneity,which promotes the emergence of treatment-refractory cancer cell populations.Focusing on how cancer cells develop resistance during the encounter with targeted drugs and the immune system,we propose a mathematical model for studying the dynamics of drug resistance in a conjoint heterogeneous tumor-immune setting.We analyze the local geometric properties of the equilibria of the model.Numerical simulations show that the selectively targeted removal of sensitive cancer cells may cause the initially heterogeneous population to become a more resistant population.Moreover,the decline of immune recruitment is a stronger determinant of cancer escape from immune surveillance or targeted therapy than the decay in immune predation strength.Sensitivity analysis of model parameters provides insight into the roles of the immune system combined with targeted therapy in determining treatment outcomes.

Immunotherapy against programmed death-1/programmed death ligand 1 in hepatocellular carcinoma: Importance of molecular variations, cellular heterogeneity, and cancer stem cells

Hepatocellular carcinoma(HCC)is a heterogeneous malignancy related to diverse etiological factors.Different oncogenic mechanisms and genetic variations lead to multiple HCC molecular classifications.Recently,an immune-based strategy using immune checkpoint inhibitors(ICIs)was presented in HCC therapy,especially with ICIs against the programmed death-1(PD-1)and its ligand PD-L1.However,despite the success of anti-PD-1/PD-L1 in other cancers,a substantial proportion of HCC patients fail to respond.In this review,we gather current information on biomarkers of anti-PD-1/PD-L1 treatment and the contribution of HCC heterogeneity and hepatic cancer stem cells(CSCs).Genetic variations of PD-1 and PD-L1 are associated with chronic liver disease and progression to cancer.PD-L1 expression in tumoral tissues is differentially expressed in CSCs,particularly in those with a close association with the tumor microenvironment.This information will be beneficial for the selection of patients and the management of the ICIs against PD-1/PD-L1.

Highlights the recent important findings in cancer heterogeneity

The therapeutic drugs,agents or techniques for the treatment of cancer could be misled since tumor tissues are frequently heterogeneous and hard to characterize.The changing of tumor microenvironments and epigenetics can mediate immunoescape and dampen the efficacy of adjuvant treatment.This short review highlights the recent important findings in cancer heterogeneity,including cancer immunology,epigenetics and genetic mutations,intratumoral microbiota and cancer stem cells,and contributing to the design of innovative cancer treatment strategy.

Next-generation sequencing traces human induced pluripotent stem cell lines clonally generated from heterogeneous cancer tissue

AIM To investigate genotype variation among induced pluripotent stem cell(iPSC) lines that were clonally generated from heterogeneous colon cancer tissues using next-generation sequencing. METHODS Human iPSC lines were clonally established by selecting independent single colonies expanded from heterogeneous primary cells of S-shaped colon cancer tissues by retroviral gene transfer(OCT3/4, SOX2, and KLF4). The ten iPSC lines, their starting cancer tissues, and the matched adjacent non-cancerous tissues were analyzed using nextgeneration sequencing and bioinformatics analysis using the human reference genome hg19. Non-synonymous single-nucleotide variants(SNVs)(missense, nonsense,and read-through) were identified within the target region of 612 genes related to cancer and the human kinome. All SNVs were annotated using dbS NP135, CCDS, RefSeq, GENCODE, and 1000 Genomes. The SNVs of the iPSC lines were compared with the genotypes of the cancerous and non-cancerous tissues. The putative genotypes were validated using allelic depth and genotype quality. For final confirmation, mutated genotypes were manually curated using the Integrative Genomics Viewer. RESULTS In eight of the ten iPSC lines, one or two non-synonymous SNVs in EIF2AK2, TTN, ULK4, TSSK1 B, FLT4, STK19, STK31, TRRAP, WNK1, PLK1 or PIK3R5 were identified as novel SNVs and were not identical to the genotypes found in the cancer and non-cancerous tissues. This result suggests that the SNVs were de novo or pre-existing mutations that originated from minor populations, such as multifocal pre-cancer(stem) cells or pre-metastatic cancer cells from multiple, different clonal evolutions, present within the heterogeneous cancer tissue. The genotypes of all ten iPSC lines were different from the mutated ERBB2 and MKNK2 genotypes of the cancer tissues and were identical to those of the noncancerous tissues and that found in the human reference genome hg19. Furthermore, two of the ten iPSC lines did not have any confirmed mutated genotypes, despite being derived from cancerous tissue. These results suggest that the traceability and preference of the starting single cells being derived from pre-cancer(stem) cells, stroma cells such as cancer-associated fibroblasts, and immune cells that co-existed in the tissues along with the mature cancer cells.CONCLUSION The genotypes of iPSC lines derived from heterogeneous cancer tissues can provide information on the type of starting cell that the iPSC line was generated from.