Stem Cell Theory of Cancer: Origin of Metastasis and Sub-clonality.

Metastasis may be the secret weapon cancer uses to dominate and subjugate, to persist and prevail. However, it is no longer a secret when we realize that a stem cell has the same ways and means to fulfill its own omnipotence and accomplish its own omnipresence… and when we realize that a cancer cell has its own version of stem-ness origin and stem-like nature. In this perspective, we discuss whether stem-ness enables metastasis or mutations drive metastasis. We ponder about low-grade versus high-grade tumors and about primary versus metastatic tumors. We wonder about stochasticity and hierarchy in the genesis and evolution of cancer and of metastasis. We postulate that metastasis may hold the elusive code that makes or breaks a stem-cell versus a genetic theory of cancer. We speculate that the vaunted model of multistep carcinogenesis may be in error and needs some belated remodeling and a major overhaul. We propose that subsequent malignant neoplasms from germ cell tumors and donor-derived malignancies in organ transplants are quintessential experiments of nature and by man that may eventually empower us to elucidate a stem-cell origin of cancer and metastasis. Unfortunately, even the best experiments of cancer and of metastasis will be left unfinished, overlooked, or forgotten, when we do not formulate a proper cancer theory derived from pertinent and illuminating clinical observations. Ultimately, there should be no consternations when we realize that metastasis has a stem-cell rather than a genetic origin, and no reservations when we recognize that metastasis has been providing us some of the most enduring tests and endearing proofs to demonstrate that cancer is indeed a stem-cell rather than a genetic disease after all.

Pembrolizumab in Patients with Advanced Metastatic Germ Cell Tumors.

LESSONS LEARNED: Advanced germ cell tumors are aggressive and associated with poor prognosis. Pembrolizumab was overall well tolerated in 12 heavily pretreated patients. Three patients had radiographic stable disease that lasted for 10.9 months, 5.5 months, and 4.5 months, respectively. Published data of immunotherapeutic agents in patients with advanced germ cell tumors are confirmed. The limited antitumor activity of immunotherapy in germ cell tumors is, at least partially, attributed to tumor biology (low tumor mutational burden; low PD-1 expression) and other poor-risk features. Tumor profiling to understand the mechanisms of resistance to pembrolizumab and innovative clinical trials that may include immunotherapy are warranted. BACKGROUND: Advanced germ cell tumors are associated with poor prognosis. We investigated the role of pembrolizumab in patients with advanced germ cell tumors. METHODS: We analyzed a prespecified cohort of an open-label, phase II clinical trial in which patients with advanced germ cell tumors were treated with pembrolizumab (200 mg) intravenously every 21 days. The endpoints of the study were the non-progression rate (NPR) at 27 weeks, safety, and tolerability. An NPR >20% was considered successful and worthy of further pursuit. RESULTS: From August 2016 to February 2018, 12 patients (10 men, 2 women) were treated (median age, 35 years [range, 22-63 years]; median number of prior systemic therapies, 3.5 [range, 2-7]; median number of metastatic sites, 3 [range, 2-8]). Overall, pembrolizumab was well tolerated. One patient experienced both grade 1 immune-related skin rash and grade 3 immune-related pneumonitis. No patient died from toxicity. Three patients had radiographic stable disease that lasted for 10.9 months, 5.5 months, and 4.5 months, respectively. No objective response was noted. The median progression-free survival was 2.4 months (95% confidence interval [CI], 1.5-4.5 months), and the median overall survival was 10.6 months (95% CI, 4.6-27.1 months). The 27-week NPR was 9.0% (95% CI, 0.23-41.2%). CONCLUSION: Overall, pembrolizumab was safe and had limited antitumor activity in these patients. In the advanced, metastatic setting, tumor profiling to understand the mechanisms of resistance to immunotherapy and innovative clinical trials to identify efficacious combination regimens rather than off-label use of pembrolizumab are warranted.

Pembrolizumab for advanced penile cancer: a case series from a phase II basket trial.

BACKGROUND: Treatment options for unresectable, locally advanced or metastatic penile squamous cell carcinoma (SCC) are limited. Previous studies have shown that 40-62% of patients with penile SCC express PD-L1. We report three cases of locally advanced or metastatic penile SCC treated with pembrolizumab. CASE PRESENTATIONS: Herein, we present three patients with recurrent, locally advanced or metastatic penile SCC who progressed on a platinum-based chemotherapy triplet and were treated with pembrolizumab, administered as part of a phase II clinical trial for rare tumors (NCT02721732). One patient with a microsatellite instability high (MSI-H) tumor experienced a durable partial response to pembrolizumab, underwent surgical consolidation, and remains disease-free 38.7 months later. Two patients experienced progressive disease within 3 months of beginning pembrolizumab. No one experienced a grade 3 or worse treatment-related adverse event. CONCLUSION: In sum, single-agent pembrolizumab was well tolerated as salvage therapy in a small cohort of patients with unresectable, locally advanced or metastatic penile SCC. Pembrolizumab produced an objective response in an MSI-H tumor, yet it did not control disease in two patients with MSS penile SCC. Rationale combination therapies, including pembrolizumab, warrant further investigation. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02721732 . Registered March 23, 2016.

Patterns of metastases of prostatic ductal adenocarcinoma.

BACKGROUND: The current study was conducted to investigate the patterns of metastases in men with metastatic prostatic ductal adenocarcinoma (DAC) and recurrence patterns after therapy. METHODS: All patients with a new diagnosis of DAC with de novo metastases and those with localized disease who developed metastases after treatment and were treated at the study institution from January 2005 to November 2018 were included. All patient and tumor characteristics and outcome data were collected. RESULTS: A total of 164 patients (37.7%) had metastatic DAC, including 112 with de novo metastases and 52 who developed metastases after treatment. Men with de novo metastases were found to have a significantly higher median prostate-specific antigen level and International Society of Urological Pathology grade but a lower cT3 and/or T4 classification compared with those with metastases that developed after treatment (all P < .05). Approximately 87% of men with de novo metastases progressed despite multiple systemic therapies, 37.6% required intervention for the palliation of symptoms, and 10.1% responded to systemic therapy and underwent treatment of the primary tumor. Men with de novo metastatic DAC and those who developed metastases after treatment had multiple metastatic sites (including bone and viscera), with higher rates of lung metastases noted in the posttreatment group (23.2% vs 44.2%; P = .01). A total of 45 patients who were treated with curative intent developed metastases at a median of 22 months (range, 0.9-74.8 months) after treatment, at low prostate-specific antigen levels (median, 4.4 ng/mL [interquartile range, 1.7-11.1 ng/mL]). CONCLUSIONS: The current study described the metastatic patterns of DAC in both patients with de novo metastatic disease and those who later progress to metastases. Men receiving treatment for DAC with curative intent require stringent long-term follow-up with imaging modalities, including chest imaging given the predilection toward lung metastases noted among these patients.

Intraoperative and early postoperative complications in postchemotherapy retroperitoneal lymphadenectomy among patients with germ cell tumors using validated grading classifications.

BACKGROUND: Postchemotherapy retroperitoneal lymphadenectomy (PC-RPLND) is an essential, yet potentially morbid, therapy for the management of patients with advanced germ cell tumors. In the current study, the authors sought to define the complication profile of PC-RPLND using validated grading systems for intraoperative adverse events (iAEs) and early postoperative complications. METHODS: Between 2000 and 2018, all patients who underwent PC-RPLND were analyzed for iAEs and early postoperative complications using the Kaafarani and Clavien-Dindo classifications, respectively. Logistic regression models were conducted to assess patient and tumor factors associated with iAEs and postoperative complications. RESULTS: Of the 453 patients identified, 115 patients (25%) and 252 patients (56%), respectively, experienced an iAE and postoperative complication. Major iAEs (grade ≥3) were observed in 15 patients (3%) and major postoperative complications (grade ≥3) were noted in 80 patients (18%). The most common iAE was vascular injury (112 of 132 events; 85%), which occurred in 92 patients (20%), and the most frequent postoperative complication was ileus, which occurred in 121 patients (27%). Original and postchemotherapy retroperitoneal mass size, nonretroperitoneal metastases, intermediate and/or poor International Germ Cell Cancer Collaborative Group classification, previous RPLND, elevated tumor markers at the time of RPLND, and anticipated adjuvant surgical procedures increased the risk of both iAEs and postoperative complications. Patients who experienced an iAE were significantly more likely to experience a postoperative complication (odds ratio, 2.50; 95% confidence interval, 1.58-3.97 [P < .001]). CONCLUSIONS: In what to the authors' knowledge is the first analysis of PC-RPLND using validated classifications for both iAEs and postoperative complications, advanced disease and surgical complexity significantly increased the risks of major iAEs and postoperative complications. Standardized reporting of adverse perioperative events allows providers and patients to appreciate the consequences of PC-RPLND during counseling and decision making.

Cabazitaxel plus carboplatin for the treatment of men with metastatic castration-resistant prostate cancers: a randomised, open-label, phase 1-2 trial.

BACKGROUND: Taxane-platinum combinations have shown promising activity in metastatic castration-resistant prostate cancers in single-group clinical studies but not in randomised trials. Distinct biological subsets of the disease might derive the greatest benefit from the addition of platinum. We aimed to determine whether adding carboplatin to cabazitaxel would improve the outcomes of men with metastatic castration-resistant prostate cancer. METHODS: We did a phase 1-2, open label, randomised study at two centres in men with progressive metastatic castration-resistant prostate cancer. In phase 1, patients received intravenous cabazitaxel 20-25 mg/m2 and intravenous carboplatin area under the curve (AUC) 3-4 mg/mL per min every 21 days. The maximum tolerated dose was defined as the highest dose cohort studied in which one of six or fewer patients experienced a dose-limiting toxicity. In phase 2, patients were randomly assigned (1:1) centrally by a computerised algorithm to intravenous cabazitaxel 25 mg/m2 with or without intravenous carboplatin AUC 4 mg/mL per min. All patients received growth factor support and oral prednisone 10 mg daily. The primary endpoints were the maximum tolerated dose of the combination in phase 1 and investigator-assessed progression-free survival in phase 2. This trial is registered at ClinicalTrials.gov, number NCT01505868. FINDINGS: Between Aug 17, 2012, and May 11, 2015, nine patients completed phase 1 as planned, and 160 were randomly assigned to cabazitaxel (n=79) or cabazitaxel plus carboplatin (n=81) in phase 2. During phase I, grade 3 adverse events were anaemia (n=2), fatigue (n=1), thrombocytopenia (n=1), hypomagnesaemia (n=1), diarrhoea (n=1), hypokalaemia (n=1), anorexia (n=1), and dehydration (n=1), and no grade 4 adverse events occurred. No dose-limiting toxicities were observed, therefore, a maximum tolerated dose of cabazitaxel of 25 mg/m2 and carboplatin of AUC 4 mg/mL per min was selected for phase 2. At a median follow-up of 31·0 months (IQR 20·5-37·1), the combination improved the median progression-free survival from 4·5 months (95% CI 3·5-5·7) to 7·3 months (95% CI 5·5-8·2; hazard ratio 0·69, 95% CI 0·50-0·95, p=0·018). In the phase 2 study, the most common grade 3-5 adverse events were fatigue (7 [9%] of 79 in the cabazitaxel group vs 16 [20%] of 81 in the combination group), anaemia (3 [4%] vs 19 [23%]), neutropenia (3 [4%] vs 13 [16%]), and thrombocytopenia (1 [1%] vs 11 [14%]). There were no treatment-related deaths. INTERPRETATION: Carboplatin added to cabazitaxel showed improved clinical efficacy compared with cabazitaxel alone for men with metastatic castration-resistant prostate cancer. Although adverse events were more common with the combination, the treatment was safe and generally well tolerated. Our data suggest that taxane-platinum combinations have a clinically beneficial role in advanced prostate cancer and a randomised phase 3 study is planned. FUNDING: Sanofi Genzyme, University of Texas MD Anderson Cancer Center Prostate Cancer Moon Shot Program, and Solon Scott III Prostate Cancer Research Fund.

Managing seminomatous and nonseminomatous germ cell tumors.

PURPOSE OF REVIEW: In the present review, we summarize the recent developments in the management of germ cell tumors (GCTs). RECENT FINDINGS: Treatment-related acute and late-onset toxicity remains a key challenge in the management of GCTs, with recent evidence showing that the adverse health outcomes of etoposide and cisplatin for four cycles in comparison to bleomycin, etoposide, and cisplatin for three cycles appear to be similar. Recent data showed that multidisciplinary clinic approach and management in experienced academic centers were associated with improved overall survival in GCT patients. There are currently multiple conventional-dose chemotherapy options for salvage therapy in patients with refractory or recurrent disease. In addition, more efficacious high-dose chemotherapy regimens continue to be developed. The role of salvage conventional-dose chemotherapy versus high-dose chemotherapy is currently being investigated prospectively. Recent reports suggested that brentuximab vedotin could be a potential salvage option for cluster of differentiation 30 positive refractory GCTs. On the other hand the results of the first phase II clinical trial investigating pembrolizumab in refractory GCTs were disappointing showing no clinical activity.Finally, deep exploration of the immune profile of GCTs using immunohistochemistry and gene expression profiling has identified that advanced GCT stage was associated with decreased T-cell and Natural killer-cell signatures, whereas T regulatory, neutrophil, mast cell, and macrophage signatures increased with advanced stage. Even though these results indicated that activated T-cell infiltration correlated with seminoma histology and good prognosis, and could be used in the future as a biomarker, this approach needs to be validated in a large cohort. SUMMARY: Remaining challenges to be addressed include minimizing therapeutic toxicity, and improving outcomes in patients with refractory/recurrent GCTs.

Recent developments in the management of germ cell tumors.

PURPOSE OF REVIEW: In the present review, we summarize the recent developments in the management of germ cell tumors (GCTs). RECENT FINDINGS: Treatment-related acute and late-onset toxicity remains a key challenge in the management of GCTs. Recent data show that patients with large retroperitoneal lymph node metastases are at increased risk of venous thromboembolism and may benefit from prophylactic anticoagulation. Predictive models have been developed to identify patients with residual retroperitoneal lymph node masses who are more likely to benefit from surgical resection. However, their clinical use remains hampered by relatively low accuracy. There are currently multiple conventional-dose chemotherapy (CDCT) options for salvage therapy in patients with refractory or recurrent disease. In addition, more efficacious high-dose chemotherapy (HDCT) regimens continue to be developed. The role of salvage CDCT versus HDCT is currently being prospectively investigated.Finally, intratumoral heterogeneity is a common finding in cancer and an obvious observation in GCTs. Despite intratumoral heterogeneity, recent studies on nonseminomatous GCT have identified distinct histological subgroups and a potentially lethal clinical phenotype. Importantly, comprehensive molecular profiling so far has not elucidated the biologic basis or the clinical underpinnings of intratumoral heterogeneity in GCTs. SUMMARY: Remaining challenges to be addressed include minimizing therapeutic toxicity and improving outcomes in patients with refractory/recurrent GCTs or malignant transformation of teratomas.

Intratumoral heterogeneity: Role of differentiation in a potentially lethal phenotype of testicular cancer.

BACKGROUND: Intratumoral heterogeneity presents a major obstacle to the widespread implementation of precision medicine. The authors assessed the origin of intratumoral heterogeneity in nonseminomatous germ cell tumor of the testis (NSGCT) and identified distinct tumor subtypes and a potentially lethal phenotype. METHODS: In this retrospective study, all consecutive patients who had been diagnosed with an NSGCT between January 2000 and December 2010 were evaluated. The histologic makeup of primary tumors and the clinical course of disease were determined for each patient. A Fine and Gray proportional hazards regression analysis was used to determine the prognostic risk factors, and the Gray test was used to detect differences in the cumulative incidence of cancer death. In a separate prospective study, next-generation sequencing was performed on tumor samples from 9 patients to identify any actionable mutations. RESULTS: Six hundred fifteen patients were included in this study. Multivariate analysis revealed that the presence of yolk sac tumor in the primary tumor (P = .0003) was associated with an unfavorable prognosis. NSGCT could be divided into 5 subgroups. Patients in the yolk sac-seminoma subgroup had the poorest clinical outcome (P = .0015). These tumors tended to undergo somatic transformation (P < .0001). Among the 9 NSGCTs that had a yolk sac tumor phenotype, no consistent gene mutation was detected. CONCLUSIONS: The current data suggest that intratumoral heterogeneity is caused in part by differentiation of pluripotent progenitor cells. Integrated or multimodal therapy may be effective at addressing intratumoral heterogeneity and treating distinct subtypes as well as a potentially lethal phenotype of NSGCT. Cancer 2016;122:1836-43. © 2016 The Authors. Cancer published by Wiley Periodicals, Inc. on behalf of American Cancer Society. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

Randomized phase 2 study of bone-targeted therapy containing strontium-89 in advanced castrate-sensitive prostate cancer.

BACKGROUND: Radiopharmaceutical use may improve the survival time of patients with castrate-resistant prostate cancer and bone metastases. Whether androgen-deprivation therapy (ADT) combined with bone-targeted therapy provides a clinical benefit to patients with advanced castrate-sensitive prostate cancer has not been investigated. METHODS: Eighty male patients were enrolled, and 79 were randomized: 40 to the control arm and 39 to the strontium-89 (Sr-89) arm. After randomization, patients in both study arms received ADT, doxorubicin, and zoledronic acid. Kaplan-Meier methodology was used to evaluate the progression-free survival (PFS) time. Multivariate Cox proportional hazards regression was used to evaluate the effects of Sr-89 after controlling for the number of bone metastases. RESULTS: The median follow-up time for the 29 patients alive at the last follow-up was 76.9 months (range, 0.07-103.4 months). The median PFS time was 18.5 months (95% confidence interval, 9.7-49.4 months) for the control arm and 12.9 months (95% confidence interval, 8.9-72.5 months) for the Sr-89 arm (P = .86). No patient developed myelodysplastic syndrome or a hematologic malignancy. An unplanned subgroup analysis suggested increased efficacy of bone-targeted therapy with a greater extent of bone involvement (ie, >6 bone metastases vs ≤6 bone metastases on the bone scan). CONCLUSIONS: The data showed that bone-targeted therapy using 1 dose of Sr-89 combined with chemohormonal ablation therapy did not favorably affect the PFS of patients with castrate-sensitive prostate cancer. The combined therapy was feasible and safe. Whether such bone-targeted therapy provides a favorable outcome for those patients with a greater tumor burden in the bone warrants further investigation.

Variant prostate carcinoma and elevated serum CA-125.

INTRODUCTION: About 10% of tumors derived from nongynecologic, noncoelomic tissues react with the OC125 antibody. Some patients with advanced prostate cancer were found to have elevated serum CA-125 level. MATERIALS AND METHODS: We examined the clinical history of 11 patients with castration resistant prostate cancer and an elevated serum CA-125 level. Pathological review and immunohistochemical staining were performed on tumors from eight of these patients. RESULTS: Patients with advanced prostate cancer and an elevated serum CA-125 level responded to androgen ablative therapy (median duration, 27 months). They were predisposed to develop persistent or recurrent urinary symptoms and visceral metastases. Eight of 11 patients had a low or undetectable serum prostate-specific antigen level (≤ 4 ng/mL) or an elevated serum carcinoembryonic antigen level (> 6 ng/mL). In 3 of 7 patients whose specimens were available for further review, the tumors contained histologic features compatible with a diagnosis of ductal or endometrioid adenocarcinoma of the prostate. CONCLUSIONS: Patients with prostate cancer and an elevated serum CA-125 level have unique clinical and pathologic characteristics. Some of these patients possess tumors compatible with a subtype of prostate cancer known as ductal adenocarcinoma. Additional studies need to be performed to elucidate the biologic basis of the various subtypes of prostate cancer.

Vascular ligand-receptor mapping by direct combinatorial selection in cancer patients.

Molecules differentially expressed in blood vessels among organs or between damaged and normal tissues, are attractive therapy targets; however, their identification within the human vasculature is challenging. Here we screened a peptide library in cancer patients to uncover ligand-receptors common or specific to certain vascular beds. Surveying ~2.35 x 10(6) motifs recovered from biopsies yielded a nonrandom distribution, indicating that systemic tissue targeting is feasible. High-throughput analysis by similarity search, protein arrays, and affinity chromatography revealed four native ligand-receptors, three of which were previously unrecognized. Two are shared among multiple tissues (integrin α4/annexin A4 and cathepsin B/apolipoprotein E3) and the other two have a restricted and specific distribution in normal tissue (prohibitin/annexin A2 in white adipose tissue) or cancer (RAGE/leukocyte proteinase-3 in bone metastases). These findings provide vascular molecular markers for biotechnology and medical applications.

Epithelioid trophoblastic tumor in male patients with germ cell tumor: A clinicopathologic analysis of five cases.

Epithelioid trophoblastic tumor (ETT) is an extremely rare chorionic-type neoplasm in the testis, with only seven cases reported in the literature. Here, we report five cases of testicular ETT from a single institution, constituting the largest series of this rare tumor to date. The patients had a mean age of 44 years (range, 20-68 years). Four patients had a previous history of testicular germ cell tumor (GCT) treated with chemotherapy, and they developed ETT in metastatic sites in a mean of 11 years (range, 3-15 years) after the initial diagnosis of testicular GCT. Only one patient had ETT in the testis. Three patients had a normal serum beta-human chorionic gonadotropin (ß-hCG) level, and two patients had a level that was slightly elevated, but far below that typically seen in patients with choriocarcinoma. ETT was characterized by a proliferation of intermediate trophoblastic cells with abundant eosinophilic cytoplasm, and the tumors frequently had coagulative necrosis with eosinophilic debris, mimicking keratinizing squamous cell carcinoma. The trophoblastic phenotype of ETT was supported by its immunoreactivity for trophoblastic markers, including GATA-3 (3 of 3 cases tested), α-inhibin (3/4), p63 (3/5), and ß-hCG (3/4). ETT was also positive for cytokeratin (4/4) and GCT marker SALL4 (3/3). Despite surgery and chemotherapy, two patients died of disease 17 months after ETT diagnosis, and three patients were alive with metastatic disease at a mean of 20 months (range, 15-28 months). Our results demonstrate that ETT may be an aggressive disease associated with distinct pathologic features and poor clinical outcome.

Stem Cell Theory of Cancer: Clinical Implications for Cellular Metabolism and Anti-Cancer Metabolomics.

Although Otto Warburg may be right about the role of glycolysis versus OXPHOS in cancer metabolism, it remains unclear whether an altered metabolism is causative or correlative and is the main driver or a mere passenger in the pathogenesis of cancer. Currently, most of our successful treatments are designed to eliminate non-cancer stem cells (non-CSCs) such as differentiated cancer cells. When the treatments also happen to control CSCs or the stem-ness niche, it is often unintended, unexpected, or undetected for lack of a pertinent theory about the origin of cancer that clarifies whether cancer is a metabolic, genetic, or stem cell disease. Perhaps cellular context matters. After all, metabolic activity may be different in different cell types and their respective microenvironments-whether it is in a normal progenitor stem cell vs. progeny differentiated cell and whether it is in a malignant CSC vs. non-CSC. In this perspective, we re-examine different types of cellular metabolism, e.g., glycolytic vs. mitochondrial, of glucose, glutamine, arginine, and fatty acids in CSCs and non-CSCs. We revisit the Warburg effect, an obesity epidemic, the aspartame story, and a ketogenic diet. We propose that a pertinent scientific theory about the origin of cancer and of cancer metabolism influences the direction of cancer research as well as the design of drug versus therapy development in cancer care.

Germ Cell Tumor of the Testis: Lethal Subtypes of a Curable Cancer.

Germ cell tumor of the testis (GCT) is a curable cancer even when it is widely metastatic; however, outcomes can differ based on tumor histology. Chemo-resistance in certain phenotypes, such as teratoma and yolk sac tumor, contributes to poor clinical outcomes in some patients with GCT. Despite this resistance to S-YSTemic therapy, many of these tumor subtypes remain amenable to surgical resection and possible cure. In this study, we report on a series of seven patients highlighting two chemo-resistant subtypes of nonseminomatous germ cell tumor (NSGCT), sarcomatoid yolk sac tumor (S-YST), and epithelioid trophoblastic tumor (ETT) for which early resection rather than additional salvage chemotherapy or high-dose intense chemotherapy might provide a superior clinical outcome and enhance cure rate.

Stem Cell Origin of Cancer: Clinical Implications beyond Immunotherapy for Drug versus Therapy Development in Cancer Care.

Although immunotherapy has revolutionized cancer care, there is still an urgent need to enhance its efficacy and ensure its safety. A correct cancer theory and proper scientific method empower pertinent cancer research and enable effective and efficient drug versus therapy development for patient care. In this perspective, we revisit the concept of immune privilege in a cancer cell versus normal cell, as well as in a cancer stem cell versus normal stem cell. We re-examine whether effective immunotherapies are efficacious due to their anti-cancer and/or immune modulatory mechanisms. We reassess why checkpoint inhibitors (CPIs) are not equal. We reconsider whether one can attribute the utility of immunotherapy to specific cancer subtypes and its futility to certain tumor/immune compartments, components, and microenvironments. We propose ways and means to advance immunotherapy beyond CPIs by combining anti-PD1/L1 with various other treatment modalities according to an appropriate scientific theory, e.g., stem cell origin of cancer, and based on available clinical evidence, e.g., randomized clinical trials. We predict that a stem cell theory of cancer will facilitate the design of better and safer immunotherapy with improved selection of its use for the right patient with the right cancer type at the right time to optimize clinical benefits and minimize potential toxic effects and complications.

Cancer: a "stem-cell" disease?

BACKGROUND: Nowadays, we believe that cancer is a genetic disease. We focus on the genetic targets and epigenetic changes in a tumor. Remarkably, many crucial signal pathways in a malignant cell involve "stem-ness" genes. The prevalence of stem-ness in cancer suggests that cancer has a stem-cell origin and is a stem-cell disease. PRESENTATION OF THE HYPOTHESIS: The observation that many innate stem-ness properties are easily interchangeable with malignant hallmarks needs to be further elucidated. There appears to be a malignant potential in every stem cell and a stem cell potential in every malignant cell. I hypothesize that cancer is a stem-cell disease rather than a genetic disease. TESTING THE HYPOTHESIS: We will use homeobox genes to endow a certain progenitor cell with specific stem-ness properties and confer different stem-cell phenotypes to the particular cell type in a hierarchical manner. We will demonstrate that an earlier homeobox gene plus a genetic defect (such as Pten loss) tend to form a more virulent tumor, while a later homeobox gene plus the same genetic defect tend to express a more indolent phenotype. Importantly, we will show that in clinically relevant cancer subtypes, those with worse clinical outcomes may paradoxically harbor fewer genetic mutations than those with better outcomes do. IMPLICATIONS OF THE HYPOTHESIS: The recognition that cancer is a stem-cell disease will instigate major paradigm shifts in our basic understanding of cancer. Many fundamental principles of oncology, such as multistep carcinogenesis, need to be reconciled. The realization that cancer is a stem-cell disease will also have profound clinical implications on personalized care. Many aspects of our current clinical trials need to be reevaluated.

Clinically atypical seminomas with yolk sac tumor features.

INTRODUCTION: A small subset of young men die from seminoma. Studying these high risk, clinically atypical seminomas (CASs)-aggressive tumors with visceral metastases and chemotherapy resistance-may provide clues to the nature of drug resistance and the origin of testicular cancers. We explored the possibility that these seminomas are a unique clinical and biologic entity with intrinsic yolk sac tumor (YST) features. MATERIALS AND METHODS: We assayed available archived tissue samples (n = 22) for chemotherapy-resistance markers found in YSTs. Specifically, we analyzed tissues and clinical histories from patients with CASs (those who had visceral metastases and recurrent disease), classical seminomas, and mixed germ-cell tumors containing YST. By using immunohistochemical testing, we evaluated the expression of bone morphogenetic protein 2, alpha fetoprotein, and glutathione S-transferase (pi) [GST (pi)]. RESULTS: GST (pi) expression significantly predicted for overall survival (p = .036). In addition, according to the results of GST (pi) immunohistochemical staining, the CASs appeared to resemble YSTs more than they did classical seminomas (p = 0.043). Less-advanced tumors, both those that expressed GST (pi) and those that were negative for GST (pi), were more amenable to local therapies, and the patients who had those tumors had better clinical outcomes. CONCLUSIONS: Results from this exploratory study suggest that certain CASs that express GST (pi) are more similar to YST than they are to classical seminomas, and that GST (pi) expression may be able to be used as a prognosticator of disease-specific survival. Such CASs thus may have a unique biologic origin that differs from that of classical seminomas. Additional studies are needed to determine the natural history and therapeutic implications of these CASs.

Stem Cell Origin of Cancer: Implications of Oncogenesis Recapitulating Embryogenesis in Cancer Care.

From this perspective, we wonder about the clinical implications of oncology recapturing ontogeny in the contexts of neoantigens, tumor biomarkers, and cancer targets. We ponder about the biological ramifications of finding remnants of mini-organs and residuals of tiny embryos in some tumors. We reminisce about classical experiments showing that the embryonic microenvironment possesses antitumorigenic properties. Ironically, a stem-ness niche-in the wrong place at the wrong time-is also an onco-niche. We marvel at the paradox of TGF-beta both as a tumor suppressor and a tumor promoter. We query about the dualism of EMT as a stem-ness trait engaged in both normal development and abnormal disease states, including various cancers. It is uncanny that during fetal development, proto-oncogenes wax, while tumor-suppressor genes wane. Similarly, during cancer development, proto-oncogenes awaken, while tumor-suppressor genes slumber. Importantly, targeting stem-like pathways has therapeutic implications because stem-ness may be the true driver, if not engine, of the malignant process. Furthermore, anti-stem-like activity elicits anti-cancer effects for a variety of cancers because stem-ness features may be a universal property of cancer. When a fetus survives and thrives despite immune surveillance and all the restraints of nature and the constraints of its niche, it is a perfect baby. Similarly, when a neoplasm survives and thrives in an otherwise healthy and immune-competent host, is it a perfect tumor? Therefore, a pertinent narrative of cancer depends on a proper perspective of cancer. If malignant cells are derived from stem cells, and both cells are intrinsically RB1 negative and TP53 null, do the absence of RB1 and loss of TP53 really matter in this whole narrative and an entirely different perspective of cancer?