A novel molecular classification method for osteosarcoma based on tumor cell differentiation trajectories

Deciphering the molecular heterogeneity of soft tissue sarcoma by integrating multiomics and single cell sequence

BACKGROUND

Soft tissue sarcoma is a highly malignant tumor with extensive heterogeneity across multiple omics. However, a comprehensive multi-omics subtyping system has not yet been established.

METHODS

We integrated sarcoma multi-omics data, including clinical information, transcriptome expression profiles, DNA methylation, and somatic mutations. Using ten advanced clustering algorithms, we identified robust subtypes and validated the reproducibility of our analysis in two independent external datasets. We also identified subtype-specific treatment strategies and analyzed the differences in microenvironments between subtypes using single-cell data.

RESULTS

Based on multi-omics subtyping, we identified two novel sarcoma molecular subtypes, named sarcoma multi-omics subtype 1 (SAMS1) and SAMS2. SAMS2 exhibited a poorer prognosis, with significantly activated Myc, glycolysis, and Wnt beta-catenin signaling pathways. SAMS2 was characterized by a lower abundance of immune cell infiltration and anti-tumor immunity deficiency, which owned a lower response rate to immunotherapy but was sensitive to certain targeted drugs, including pazopanib, axitinib, thapsigargin, and elesclomol. MK886 and NU1025 were identified as effective therapeutic targets for the SAMS2. In SAMS2-like tumor epithelial cells, HOXB13/COL16A1 and BASP1 regulated epithelial-mesenchymal transition. We found that WNT7B was highly expressed in STS and was associated with poor patient prognosis, suggesting its potential as a novel therapeutic target for STS patients.

CONCLUSION

The STS molecular subtyping system based on multi-omics data effectively distinguishes patients with poor prognosis. The subtyping results are robust and reliable, providing new insights for the precise diagnosis and treatment of these patients.

Insights into the osteosarcoma microenvironment: Multiscale analysis of structural and mineral heterogeneity

Osteosarcoma (OS) is a malignant and heterogeneous disease that typically originates in the long bones of children and adolescents. It is characterized by the presence of immature cells having an aggressive phenotype and rapid uncontrolled proliferation. OS progression induces significant molecular and cellular changes locally within the bone, resulting in the development of an abnormal tumor microenvironment (TME). The OS TME plays a crucial role in tumor progression and development, however, the precise effects of OS on bone structure and mineralization still remain poorly understood. In this study, we examined the OS TME by analyzing samples from osteoblastic, parosteal, and periosteal osteosarcomas. Employing advanced synchrotron-based X-ray techniques, we performed a multiscale analysis to evaluate the structural and mineral complexity of tumor-affected bone. Our results revealed marked morphological differences among the osteosarcoma subtypes, while confirming that biomineralization remains active through the production of hydroxyapatite (HA). X-ray diffraction identified two distinct hydroxyapatite crystalline phases across all samples, suggesting a critical behavior of minerals in bone. Additionally, we observed that the bone mineral structure in periosteal and parosteal osteosarcomas exhibited crystal deformations along the c-axis, whereas the osteoblastic osteosarcoma displayed a mineral profile comparable to control bone. Micro-X-ray absorption near-edge spectroscopy revealed the occurrence of a dysregulated biomineralization in the parosteal and periosteal subtypes, marked by the presence of calcium compounds different from HA, in contrast to the mature mineral state found in the osteoblastic variant. These findings highlight the complexity of osteosarcoma repercussion on bone tissue, offering new insights into the interactions within the OS TME. STATEMENT OF SIGNIFICANCE: This study investigates the tumor microenvironment (TME) of osteosarcoma (OS), a rare and aggressive bone cancer mainly affecting children and adolescents. Using advanced synchrotron-based X-ray techniques, we analyzed structural and mineral alterations in bone from three OS subtypes: osteoblastic, parosteal, and periosteal. The results reveal distinct subtype-specific differences in bone mineralization and crystallinity, highlighting the heterogeneity of OS and the pivotal role of its microenvironment in driving disease progression. This research contributes to our understanding of OS pathophysiology and provides foundation for future studies aimed at developing targeted therapies and improving diagnostic approaches.

Targeting cancer-induced skeletal damage: a holistic approach to understanding pathophysiology, mechanisms, and management solutions

Cancer's insidious reach extends far beyond its initial site, particularly manifesting in the skeleton, where it precipitates a spectrum of pathological conditions ranging from bone metastases and cachexia to primary bone cancers. This review highlights the critical impact of cancer on skeletal health, including the development of bone metastases, cachexia, and primary bone cancers, underscoring the importance of understanding the complex interaction between cancer and the bones. It emphasizes the global burden of cancer and its skeletal complications, which severely affect quality of life. The article reviews the prevalence of bone metastases in various cancers, such as breast, prostate, lung, renal cancers, and multiple myeloma, and stresses the need for targeted treatments. It also discusses the mechanisms behind tumor spread to bones and the systemic effects of cancer, including reduced bone mineral density and increased fracture risk, even without direct bone invasion. The challenges posed by primary bone cancers, which are rarer but highly aggressive, are also examined, highlighting the role of genetics and molecular research in treatment development. The review calls for a multidisciplinary approach to manage the severe symptoms of cancer-induced bone damage and explores the potential of personalized medicine to improve treatment outcomes. It concludes by advocating for continued research and collaboration to develop more precise and personalized therapies for cancer-related bone issues, aiming to improve the lives of those affected.

Microenvironment matters: insights from the FOSTER consortium on microenvironment-driven approaches to osteosarcoma therapy

Osteosarcoma (OS), a prevalent malignant bone tumor, has seen limited progress in treatment efficacy and patient outcomes over decades. Recent insights into the tumor microenvironment (TME) have revealed its crucial role in tumor progression and therapeutic resistance, particularly in OS. This review offers a comprehensive exploration of the OS microenvironment, meticulously dissecting its crucial components: the mesenchymal stromal TME, the immune microenvironment, hypoxia-induced adaptations, and the impact of the physical microenvironment. By demonstrating how these elements collectively drive tumor proliferation, immune evasion, and invasion, this review explores the intricate molecular and cellular dynamics at play. Furthermore, innovative approaches targeting the OS microenvironment, such as immunotherapies, are presented. This review highlights the importance of the TME in OS progression and its potential as a source of novel therapeutic strategies, offering new hope for improved patient outcomes.

Callus organoids reveal distinct cartilage to bone transition mechanisms across donors and a role for biological sex

Clinical translation of tissue-engineered advanced therapeutic medicinal products is hindered by a lack of patient-dependent and independent in-process biological quality controls that are reflective of in vivo outcomes. Recent insights into the mechanism of native bone repair highlight a robust path dependence. Organoid-based bottom-up developmental engineering mimics this path-dependence to design personalized living implants scaffold-free, with in-build outcome predictability. Yet, adequate (noninvasive) quality metrics of engineered tissues are lacking. Moreover, insufficient insight into the role of donor variability and biological sex as influencing factors for the mechanism toward bone repair hinders the implementation of such protocols for personalized bone implants. Here, male and female bone-forming organoids were compared to non-bone-forming organoids regarding their extracellular matrix composition, transcriptome, and secreted proteome signatures to directly link in vivo outcomes to quality metrics. As a result, donor variability in bone-forming callus organoids pointed towards two distinct pathways to bone, through either a hypertrophic cartilage or a fibrocartilaginous template. The followed pathway was determined early, as a biological sex-dependent activation of distinct progenitor populations. Independent of donor or biological sex, a cartilage-to-bone transition was driven by a common panel of secreted factors that played a role in extracellular matrix remodeling, mineralization, and attraction of vasculature. Hence, the secreted proteome is a source of noninvasive biomarkers that report on biological potency and could be the missing link toward data-driven decision-making in organoid-based bone tissue engineering.

Substrate stiffness modulates osteogenic and adipogenic differentiation of osteosarcoma through PIEZO1 mediated signaling pathway

Most osteosarcoma (OS) cases exhibit poor differentiation at the histopathological level. Disruption of the normal osteogenic differentiation process results in the unregulated proliferation of precursor cells, which is a critical factor in the development of OS. Differentiation therapy aims to slow disease progression by restoring the osteogenic differentiation process of OS cells and is considered a new approach to treating OS. However, there are currently few studies on the mechanism of differentiation of OS, which puts the development of differentiation therapeutic drugs into a bottleneck. Substrate stiffness can regulate differentiation in mesenchymal stem cells. Evidence supports that mesenchymal stem cells and osteoblast precursors are the origin of OS. In this study, we simulated different stiffnesses in vitro to investigate the mechanism of substrate stiffness affecting differentiation of OS. We demonstrate that Piezo type mechanosensitive ion channel component 1 (PIEZO1) plays a critical regulatory role in sensing substrate stiffness in osteogenic and adipogenic differentiation of OS. When OS cells are cultured on the stiff substrate, integrin subunit beta 1 (ITGB1) increases and cooperates with PIEZO1 to promote Yes-Associated Protein (YAP) entering the nucleus, and may inhibit EZH2, thereby inhibiting H3K27me3 and increasing RUNX2 expression, and cells differentiate toward osteogenesis. Our results provide new insights for research on differentiation treatment of OS and are expected to help identify new targets for future drug design.

Bone Matrix-forming Tumors

Bone matrix-forming tumors are a group of neoplasms that exhibit differentiation toward any stage of osteoblast development. Their clinicopathologic features can resemble one another, yet their clinical management may vary significantly. Therefore, appropriate treatment requires accurate diagnosis, which can be challenging, especially with limited biopsy specimens. Recently, the driver genetic alterations underlying these neoplasms have been discovered, and their protein products can be targeted for diagnosis and therapy. Herein, we summarize the recent advances in our understanding of bone matrix-forming tumors and emphasize the integration of molecular genetics into their conventional clinicopathologic evaluation.

Integrated analysis of single-cell and bulk transcriptomics reveals cellular subtypes and molecular features associated with osteosarcoma prognosis

BACKGROUND

Osteosarcoma (OS) is the most common primary bone malignancy with variable molecular biology and prognosis. However, our understanding of the association between cell types and OS progression remains poor.

METHODS

We generated a human OS cell atlas by integrating over 110,000 single cells from 17 samples. Multiple machine learning algorithms were applied to develop tumor purity prediction models based on transcriptomic profile of OS. The Scissor algorithm and gene enrichment analyses were conducted to delve into cell-intrinsic molecular characteristics linked to OS prognosis. Moreover, the study investigated the impact of ATF6α in OS aggressiveness through genetic and pharmacological loss of function analyses. Lastly, the CellChat algorithm was employed to investigate cell-cell communications.

RESULTS

Utilizing the high-quality human OS cell atlas, we identified tumor purity as a prognostic indicator and developed a robust tumor purity prediction model. We respectively delineated cancer cell- and immune cell-intrinsic molecular characteristics associated with OS prognosis at single-cell resolution. Interestingly, tumor cells with activated unfolded protein response (UPR) pathway were significantly associated with disease aggressiveness. Notably, ATF6α emerged as the top-activated transcription factor for this tumor subcluster. Subsequently, we confirmed that ATF6α was markedly associated with OS progression, while both genetic and pharmacological inhibition of ATF6α impaired the survival of HOS cells. Lastly, we depicted the landscape of signal crosstalk between the UPR-related subcluster and other cell types within the tumor microenvironment.

CONCLUSION

In summary, our work provides novel insights into the molecular biology of OS, and offers valuable resource for OS biomarker discovery and treatment strategy development.

Single-Cell Transcriptomic Analysis Reveals Biomechanical Loading-Induced Imbalance in Bone and Fat, Leading to Ossification in Lumbar Intervertebral Disc Nucleus Pulposus Degeneration

In this study, we explored the impact of different biomechanical loadings on lumbar spine motion segments, particularly concerning intervertebral disc degeneration (IVDD). We aimed to uncover the cellular milieu and mechanisms driving ossification in the nucleus pulposus (NP) during IVDD, a process whose underlying mechanisms have remained elusive. The study involved the examination of fresh NP tissue from the L3-S1 segment of five individuals, either with IVDD or healthy. The analysis consisted of histopathological evaluation and single-cell RNA sequencing. To further validate the impact of biomechanical loading on IVDD, particularly on the CITED4 + METRN + NP chondrocytes and the bone-fat balance mechanism, a retrospective analysis was conducted using paraffin-embedded NP samples from patients. A distinct subset of CITED4 + METRN+ chondrocytes in the degenerated NP that were influenced by biomechanical loading was identified. These cells were evaluated for their potential as diagnostic biomarkers. Pseudotemporal analysis indicated that inflammation and repair processes were integral to NP ossification. Notably, the L4/5 and L5/S1 segments with severe IVDD showed pronounced ossification and heightened lipogenic metabolism. Cell communication analysis sheds light on the roles of bone-fat balance proteins and various ossification genes. Additionally, immunohistochemistry and immunofluorescence confirmed that biomechanical loading intensified IVDD by fostering osteogenic differentiation, mediated by macrophage migration inhibitory factor (MIF)-regulated bone-fat balance. This research reveals the microenvironmental factors of IVDD NP ossification under biomechanical loading, highlighting the role of bone-fat imbalance. These insights significantly enhance the understanding of IVDD pathogenesis and pave the way for innovative therapeutic approaches.

Analysis of metastasis‑related risk factors and clinical relevance in adult soft‑tissue sarcoma

Metastasis occurs in nearly 50% of cases of adult soft-tissue sarcoma (ASTS), leading to a dismal prognosis, with a 2-year survival rate of ~30%. Consequently, a prognostic model that incorporates metastatic characteristics may be instrumental in predicting survival time and in crafting optimal personalized therapeutic strategies for patients with ASTS. In the present study, a prognostic prediction model for ASTS was developed by examining genes that are differentially expressed between non-metastatic and metastatic patients in the Gene Expression Omnibus dataset. The prognostic model, which includes five featured genes [actin γ2 (ACTG2), apolipoprotein D, coatomer protein complex subunit γ2 imprinted transcript 1, collagen type VI α6 chain and osteomodulin], was further validated in patients with ASTS from the Cancer Genome Atlas dataset. Based on these five-gene signatures, patients were categorized into high- and low-risk groups. Functional and pathway analyses revealed disparities in stemness, extracellular matrix and cell adhesion-related pathways between the two risk groups, particularly noting the activation of the PI3K-Akt pathway in high-risk cases. Analysis of immune infiltration also revealed variations in immune microenvironment changes between the two risk groups. Immunohistochemical staining substantiated the prognostic significance of these gene signatures in a specific sarcoma subtype. Additionally, wound-healing and Transwell assays demonstrated that inhibition of ACTG2 by shRNAs curbed cell migration and invasion in a sarcoma HOS cell line, underscoring its role in sarcoma metastasis. In conclusion, the present study successfully developed and validated a metastasis-based prognosis prediction model. This model not only reliably forecasts the survival of patients with ASTS, but also may pave the way for further investigation into the processes underlying sarcoma metastasis, ultimately aiding in the design of tailored therapeutic regimens.

Diagnostic value of combined detection of AKP, TSGF, and LDH for pediatric osteosarcoma: a case-control study

OBJECTIVE

To evaluate the diagnostic value of serum alkaline phosphatase (AKP), tumor-supplied growth factor group (TSGF), and lactate dehydrogenase (LDH) for pediatric osteosarcoma.

METHODS

A retrospective analysis of clinical data from 81 pediatric osteosarcoma patients (osteosarcoma group) and 63 patients with benign bone tumors (benign bone tumor group) admitted to Yantaishan Hospital from February 2023 to November 2023 was conducted. Basic and clinical data differences between the two groups of children were compared. A multivariate regression model was established to determine predictive factors for pediatric osteosarcoma, and the diagnostic value of identified indicators for pediatric osteosarcoma was evaluated.

RESULTS

Osteosarcoma group demonstrated significantly higher serum AKP (375.76±73.47 vs 286.12±76.50 U/L), TSGF (69.01±16.30 vs 53.57±16.37 U/mL), and LDH (269.55±66.96 vs 207.46±59.20 U/L) levels as compared to the benign bone tumor group. Correlation analysis suggested significant positive correlations between AKP (rho=0.505), TSGF (rho=406), LDH (rho=0.449) and pediatric osteosarcoma. Multivariate regression analysis showed serum AKP, TSGF, and LDH were independent predictive factor for pediatric osteosarcoma. The AUC value for AKP was 0.794, with a Youden index of 0.459; the AUC value for TSGF was 0.736, with a Youden index of 0.406; and the AUC value for LDH was 0.761, with a Youden index of 0.462. The combined use of these three biomarkers yielded an AUC of 0.886.

CONCLUSION

The combined detection of serum AKP, TSGF, and LDH can enhance the diagnostic accuracy of pediatric osteosarcoma, providing important evidence for clinical treatment.

Single-cell RNA sequencing reveals the cellular and molecular heterogeneity of treatment-naïve primary osteosarcoma in dogs

Osteosarcoma (OS) is a heterogeneous, aggressive malignancy of the bone that disproportionally affects children and adolescents. Therapeutic interventions for OS are limited, which is in part due to the complex tumor microenvironment (TME). As such, we used single-cell RNA sequencing (scRNA-seq) to describe the cellular and molecular composition of the TME in 6 treatment-naïve dogs with spontaneously occurring primary OS. Through analysis of 35,310 cells, we identified 41 transcriptomically distinct cell types including the characterization of follicular helper T cells, mature regulatory dendritic cells (mregDCs), and 8 tumor-associated macrophage (TAM) populations. Cell-cell interaction analysis predicted that mregDCs and TAMs play key roles in modulating T cell mediated immunity. Furthermore, we completed cross-species cell type gene signature homology analysis and found a high degree of similarity between human and canine OS. The data presented here act as a roadmap of canine OS which can be applied to advance translational immuno-oncology research.

WWOX promotes osteosarcoma development via upregulation of Myc

Osteosarcoma is an aggressive bone tumor that primarily affects children and adolescents. This malignancy is highly aggressive, associated with poor clinical outcomes, and primarily metastasizes to the lungs. Due to its rarity and biological heterogeneity, limited studies on its molecular basis exist, hindering the development of effective therapies. The WW domain-containing oxidoreductase (WWOX) is frequently altered in human osteosarcoma. Combined deletion of Wwox and Trp53 using Osterix1-Cre transgenic mice has been shown to accelerate osteosarcoma development. In this study, we generated a traceable osteosarcoma mouse model harboring the deletion of Trp53 alone (single-knockout) or combined deletion of Wwox/Trp53 (double-knockout) and expressing a tdTomato reporter. By tracking Tomato expression at different time points, we detected the early presence of tdTomato-positive cells in the bone marrow mesenchymal stem cells of non-osteosarcoma-bearing mice (young BM). We found that double-knockout young BM cells, but not single-knockout young BM cells, exhibited tumorigenic traits both in vitro and in vivo. Molecular and cellular characterization of these double-knockout young BM cells revealed their resemblance to osteosarcoma tumor cells. Interestingly, one of the observed significant transcriptomic changes in double-knockout young BM cells was the upregulation of Myc and its target genes compared to single-knockout young BM cells. Intriguingly, Myc-chromatin immunoprecipitation sequencing revealed its increased enrichment on Myc targets, which were upregulated in double-knockout young BM cells. Restoration of WWOX in double-knockout young BM cells reduced Myc protein levels. As a prototype target, we demonstrated the upregulation of MCM7, a known Myc target, in double-knockout young BM relative to single-knockout young BM cells. Inhibition of MCM7 expression using simvastatin resulted in reduced proliferation and tumor cell growth of double-knockout young BM cells. Our findings reveal BM mesenchymal stem cells as a platform to study osteosarcoma and Myc and its targets as WWOX effectors and early molecular events during osteosarcomagenesis.

Single-Nuclei Multiome (ATAC + Gene Expression) Sequencing of a Primary Canine Osteosarcoma Elucidates Intra-Tumoral Heterogeneity and Characterizes the Tumor Microenvironment

Osteosarcoma (OSA) is a highly aggressive bone tumor primarily affecting pediatric or adolescent humans and large-breed dogs. Canine OSA shares striking similarities with its human counterpart, making it an invaluable translational model for uncovering the disease's complexities and developing novel therapeutic strategies. Tumor heterogeneity, a hallmark of OSA, poses significant challenges to effective treatment due to the evolution of diverse cell populations that influence tumor growth, metastasis, and resistance to therapies. In this study, we apply single-nuclei multiome sequencing, encompassing ATAC (Assay for Transposase-Accessible Chromatin) and GEX (Gene Expression, or RNA) sequencing, to a treatment-naïve primary canine osteosarcoma. This comprehensive approach reveals the complexity of the tumor microenvironment by simultaneously capturing the transcriptomic and epigenomic profiles within the same nucleus. Furthermore, these results are analyzed in conjunction with bulk RNA sequencing and differential analysis of the same tumor and patient-matched normal bone. By delving into the intricacies of OSA at this unprecedented level of detail, we aim to unravel the underlying mechanisms driving intra-tumoral heterogeneity, opening new avenues for therapeutic interventions in both human and canine patients. This study pioneers an approach that is broadly applicable, while demonstrating significant heterogeneity in the context of a single individual's tumor.

Single-cell RNA sequencing reveals the cellular and molecular heterogeneity of treatment-naïve primary osteosarcoma in dogs

Osteosarcoma (OS) is a heterogeneous, aggressive malignancy of the bone that disproportionally affects children and adolescents. Therapeutic interventions for OS are limited, which is in part due to the complex tumor microenvironment (TME) that has proven to be refractory to immunotherapies. Thus, there is a need to better define the complexity of the OS TME. To address this need, we used single-cell RNA sequencing (scRNA-seq) to describe the cellular and molecular composition of the TME in 6 treatment-naïve dogs with spontaneously occurring primary OS. Through analysis of 35,310 cells, we identified 30 distinct immune cell types, 9 unique tumor populations, 1 cluster of fibroblasts, and 1 cluster of endothelial cells. Independent reclustering of major cell types revealed the presence of follicular helper T cells, mature regulatory dendritic cells (mregDCs), and 8 transcriptomically distinct macrophage/monocyte populations. Cell-cell interaction inference analysis predicted that mregDCs and tumor-associated macrophages (TAMs) play key roles in modulating T cell mediate immunity. Furthermore, we used publicly available human OS scRNA-seq data to complete a cross-species cell type gene signature homology analysis. The analysis revealed a high degree of cell type gene signature homology between species, suggesting the cellular composition of OS is largely conserved between humans and dogs. Our findings provide key new insights into the biology of canine OS and highlight the conserved features of OS across species. Generally, the data presented here acts as a cellular and molecular roadmap of canine OS which can be applied to advance the translational immuno-oncology research field.

Signal Pathways and microRNAs in Osteosarcoma Growth and the Dual Role of Mesenchymal Stem Cells in Oncogenesis

The major challenges in Osteosarcoma (OS) therapy are its heterogeneity and drug resistance. The development of new therapeutic approaches to overcome the major growth mechanisms of OS is urgently needed. The search for specific molecular targets and promising innovative approaches in OS therapy, including drug delivery methods, is an urgent problem. Modern regenerative medicine focuses on harnessing the potential of mesenchymal stem cells (MSCs) because they have low immunogenicity. MSCs are important cells that have received considerable attention in cancer research. Currently, new cell-based methods for using MSCs in medicine are being actively investigated and tested, especially as carriers for chemotherapeutics, nanoparticles, and photosensitizers. However, despite the inexhaustible regenerative potential and known anticancer properties of MSCs, they may trigger the development and progression of bone tumors. A better understanding of the complex cellular and molecular mechanisms of OS pathogenesis is essential to identify novel molecular effectors involved in oncogenesis. The current review focuses on signaling pathways and miRNAs involved in the development of OS and describes the role of MSCs in oncogenesis and their potential for antitumor cell-based therapy.

Shedding Light on Osteosarcoma Cell Differentiation: Impact on Biomineralization and Mitochondria Morphology

Osteosarcoma (OS) is the most common primary malignant bone tumor and its etiology has recently been associated with osteogenic differentiation dysfunctions. OS cells keep a capacity for uncontrolled proliferation showing a phenotype similar to undifferentiated osteoprogenitors with abnormal biomineralization. Within this context, both conventional and X-ray synchrotron-based techniques have been exploited to deeply characterize the genesis and evolution of mineral depositions in a human OS cell line (SaOS-2) exposed to an osteogenic cocktail for 4 and 10 days. A partial restoration of the physiological biomineralization, culminating with the formation of hydroxyapatite, was observed at 10 days after treatment together with a mitochondria-driven mechanism for calcium transportation within the cell. Interestingly, during differentiation, mitochondria showed a change in morphology from elongated to rounded, indicating a metabolic reprogramming of OS cells possibly linked to an increase in glycolysis contribution to energy metabolism. These findings add a dowel to the genesis of OS giving new insights on the development of therapeutic strategies able to restore the physiological mineralization in OS cells.

Mucormycosis (black fungus) ensuing COVID-19 and comorbidity meets - Magnifying global pandemic grieve and catastrophe begins

Post COVID-19, mucormycosis occurred after the SARS-CoV-2 has rampaged the human population and is a scorching problem among the pandemic globally, particularly among Asian countries. Invasive mucormycosis has been extensively reported from mild to severe COVID-19 survivors. The robust predisposing factor seems to be uncontrolled diabetes mellitus, comorbidity and immunosuppression acquired through steroid therapy. The prime susceptive reason for the increase of mucormycosis cases is elevated iron levels in the serum of the COVID survivors. A panoramic understanding of the infection has been elucidated based on clinical manifestation, genetic and non- genetic mechanisms of steroid drug administration, biochemical pathways and immune modulated receptor associations. This review lime-lights and addresses the "What", "Why", "How" and "When" about the COVID-19 associated mucormycosis (CAM) in a comprehensive manner with a pure intention to bring about awareness to the common public as the cases are inevitably and exponentially increasing in India and global countries as well. The article also unearthed the pathogenesis of mucormycosis and its association with the COVID-19 sequela, the plausible routes of entry, diagnosis and counter remedies to keep the infection at bay. Cohorts of case reports were analysed to spotlight the link between the pandemic COVID-19 and the nightmare-mucormycosis.