Pancreatic cancer is one of the deadliest human malignancies and little progress has been achieved in its treatment over the past decades. Advances in our understanding of the biology of this disease ...provide new potential opportunities for treatment. Pancreatic cancer is preceded by precursor lesions, the most common of which are known as Pancreatic Intraepithelial Neoplasia (PanIN). PanIN lesions, which are the focus of this review, have a high incidence of Kras mutations, and Kras mutations are a hallmark of the late-stage disease. We now know from genetically engineered mouse models that oncogenic Kras is not only driving the formation of pancreatic cancer precursor lesions, but it is also required for their progression, and for the maintenance of invasive and metastatic disease. Thus, an enormous effort is being placed in generating Kras inhibitors for clinical use. Additionally, alternative approaches, including understanding the role of Kras effector pathways at different stages of the disease progression, are being devised to target Kras effector pathways therapeutically. In particular, efforts have focused on the MAPK pathway and the PI3K pathway, for which inhibitors are widely available. Finally, recent studies have highlighted the need for oncogenic Kras to establish feedback mechanisms that maintain its levels of activity; the latter might constitute alternative ways to target Kras in pancreatic cancer. Here, we will review recent basic research and discuss potential therapeutic applications.
Glycine-12 mutations in the GTPase KRAS (KRAS
G12
) are an initiating event for development of lung adenocarcinoma (LUAD). KRAS
G12
mutations promote cell-intrinsic rewiring of alveolar type-II ...progenitor (AT2) cells, but to what extent such changes interplay with lung homeostasis and cell fate pathways is unclear. Here, we generated single-cell RNA-seq (scRNA-seq) profiles from AT2-mesenchyme organoid co-cultures, mice, and stage-IA LUAD patients, identifying conserved regulators of AT2 transcriptional dynamics and defining the impact of KRAS
G12D
mutation with temporal resolution. In AT2
WT
organoids, we found a transient injury/plasticity state preceding AT2 self-renewal and AT1 differentiation. Early-stage AT2
KRAS
cells exhibited perturbed gene expression dynamics, most notably retention of the injury/plasticity state. The injury state in AT2
KRAS
cells of patients, mice, and organoids was distinguishable from AT2
WT
states via altered receptor expression, including co-expression of ITGA3 and SRC. The combination of clinically relevant KRAS
G12D
and SRC inhibitors impaired AT2
KRAS
organoid growth. Together, our data show that an injury/plasticity state essential for lung repair is co-opted during AT2 self-renewal and LUAD initiation, suggesting that early-stage LUAD may be susceptible to interventions that target specifically the oncogenic nature of this cell state.
Synopsis
KRAS
G12
mutations promote cell-intrinsic rewiring of alveolar type II progenitor (AT2) cells, but to what extent such changes interplay with lung homeostasis and cell fate pathways is unclear. This study investigates the epigenetic and transcriptomic responses of AT2 cells to specific oncogenic events.
AT2
WT
organoids adopt a transient, transitional injury/plasticity state prior to both AT2 self-renewal and AT1 differentiation.
AT2
KRAS
cells co-opt and retain the transitional injury/plasticity state.
AT2
KRAS
cells in patients, mice, and organoids differ from AT2WT cells by altered gene expression, including co-expression of ITGA3 and SRC.
AT2
KRAS
cells in patients, mice, and organoids can be targeted using clinically-relevant KRASG12D and SRC inhibitors.
KRAS
G12
mutations cause persistence of a normally transient injury/plasticity state in progenitor cells, leading to initiation of lung adenocarcinoma.
CDK4 is emerging as a target in
-mutant non-small cell lung cancer (NSCLC). We demonstrate that
-mutant NSCLC cell lines are initially sensitive to the CDK4/6 inhibitor palbociclib, but readily ...acquire resistance associated with increased expression of CDK6, D-type cyclins and cyclin E. Resistant cells also demonstrated increased ERK1/2 activity and sensitivity to MEK and ERK inhibitors. Moreover, MEK inhibition reduced the expression and activity of cell cycle proteins mediating palbociclib resistance. In resistant cells, ERK activated mTOR, driven in part by upstream FGFR1 signaling resulting from the extracellular secretion of FGF ligands. A genetically-engineered mouse model of
-mutant NSCLC initially sensitive to palbociclib similarly developed acquired resistance with increased expression of cell cycle mediators, ERK1/2 and FGFR1. In this model, resistance was delayed with combined palbociclib and MEK inhibitor treatment. These findings implicate an FGFR1-MAP kinase-mTOR pathway resulting in increased expression of D-cyclins and CDK6 that confers palbociclib resistance and indicate that CDK4/6 inhibition acts to promote MAP kinase dependence.
Previous studies have identified 2 clinically significant morphologic subtypes of intrahepatic cholangiocarcinoma (ICC) on the basis of anatomic location and/or histologic appearances. Recognizing ...that these classification schemes are not always applicable practically, this study aimed to establish a novel classification system based on mucin productivity and immunophenotype and to determine the rationale of this classification by examining the clinicopathologic and genetic characteristics of the 2 subtypes defined by this method. We retrospectively investigated 102 consecutive ICC cases and classified them on the basis of mucin productivity and immunophenotype (S100P, N-cadherin, and NCAM). We found that 42 and 56 cases were classified as type 1 and type 2 ICCs, respectively, and only 4 cases were of indeterminate type. Type 1 ICC, generally characterized by mucin production and diffuse immunoreactivity to S100P, arose less frequently in chronic liver diseases and showed higher levels of serum CEA and CA 19-9 than did type 2 ICC, which generally showed little mucin production and exhibited immunoreactivity to N-cadherin and/or NCAM. Type 1 ICC was characterized by several pathologic features, including higher frequencies of perineural invasion and lymph node metastasis. Although the log-rank test demonstrated that type 1 ICC had significantly worse survival, the multivariate Cox regression analysis showed no prognostic significance of this histologic subtype. Genetic analyses revealed that KRAS mutation was significantly more frequent in type 1 ICC, whereas IDH mutation and FGFR2 translocation were restricted to type 2 ICC. In conclusion, the present classification of ICC based on mucin productivity and immunophenotype identified 2 subtypes with clinicopathologic significance.
CAsE-PE cells are an arsenic-transformed, human prostate epithelial line containing oncogenic mutations in KRAS compared to immortalized, normal KRAS parent cells, RWPE-1. We previously reported ...increased copy number of mutated KRAS in CAsE-PE cells, suggesting gene amplification. Here, KRAS flanking genomic and transcriptomic regions were sequenced in CAsE-PE cells for insight into KRAS amplification. Comparison of DNA-Seq and RNA-Seq showed increased reads from background aligning to all KRAS exons in CAsE-PE cells, while a uniform DNA-Seq read distribution occurred in RWPE-1 cells with normal transcript expression. We searched for KRAS fusions in DNA and RNA sequencing data finding a portion of reads aligning to KRAS and viral sequence. After generation of cDNA from total RNA, short and long KRAS probes were generated to hybridize cDNA and KRAS enriched fragments were PacBio sequenced. More KRAS reads were captured from CAsE-PE cDNA versus RWPE-1 by each probe set. Only CAsE-PE cDNA showed KRAS viral fusion transcripts, primarily mapping to LTR and endogenous retrovirus sequences on either 5′- or 3′-ends of KRAS. Most KRAS viral fusion transcripts contained 4 to 6 exons but some PacBio sequences were in unusual orientations, suggesting viral insertions within the gene body. Additionally, conditioned media was extracted for potential retroviral particles. RNA-Seq of culture media isolates identified KRAS retroviral fusion transcripts in CAsE-PE media only. Truncated KRAS transcripts suggested multiple retroviral integration sites occurred within the KRAS gene producing KRAS retroviral fusions of various lengths. Findings suggest activation of endogenous retroviruses in arsenic carcinogenesis should be explored.
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•Mutated KRAS is an oncogenic driver in CAsE-PE human prostate cancer cells.•DNA-Seq, RNA-Seq showed KRAS viral fusions transcripts embedded in CAsE-PE genome.•KRAS pull-down of cDNA revealed viral-fusion transcripts only in CAsE-PE cells.•Extracts of CAsE-PE culture media identified KRAS retroviral fusion transcripts.•Activation of endogenous retroviruses in arsenic carcinogenesis should be explored.
This randomized study was designed to investigate the superiority of gemcitabine (gem) plus nimotuzumab (nimo), an anti-epidermal growth factor receptor monoclonal antibody, compared with gem plus ...placebo as first-line therapy in patients with advanced pancreatic cancer.
Patients with previously untreated, unresectable, locally advanced or metastatic pancreatic cancer were randomly assigned to receive gem: 1000 mg/m2, 30-min i.v. once weekly (d1, 8, 15; q29) and nimo: fixed dose of 400 mg once weekly as a 30-min infusion, or gem plus placebo, until progression or unacceptable toxicity. The primary end point was overall survival (OS), secondary end points included time to progression, overall response rate, safety and quality of life.
A total of 192 patients were randomized, with 186 of them being assessable for efficacy and safety (average age 63.6 years). One-year OS/progression-free survival (PFS) was 34%/22% for gem plus nimo compared with 19%/10% for gem plus placebo (HR = 0.69;P = 0.03/HR = 0.68;P = 0.02). Median OS/PFS was 8.6/5.1 months for gem plus nimo versus 6.0/3.4 mo in the gem plus placebo group (HR = 0.69;P = 0.0341/HR = 0.68;P = 0.0163), with very few grade 3/4 toxicities.KRAS wildtype patients experienced a significantly better OS than those withKRAS mutations (11.6 versus 5.6 months,P = 0.03).
This randomized study showed that nimo in combination with gem is safe and well tolerated. The 1-year OS and PFS rates for the entire population were significantly improved. Especially, those patients withKRAS wildtype seem to benefit.
The study was registered as protocol ID OSAG101-PCS07, NCT00561990 and EudraCT 2007-000338-38.
Pancreatic ductal adenocarcinomas (PDA) are extremely aggressive cancers and currently available therapies are only minimally effective in treating this disease. Tackling this devastating cancer has ...been a major challenge to the scientific and medical communities, in part due to its intense therapeutic resistance. One of the aspects of this tumor that contributes to its aggressive behavior is its altered cellular metabolism. Indeed, PDA cells seem to possess the ability to adapt their metabolism to the particular environment to which they are exposed, including utilizing diverse fuel sources depending on their availability. Moreover, PDA tumors are efficient at recycling various metabolic substrates through activation of different salvage pathways such as autophagy and macropinocytosis. Together, these diverse metabolic adaptations allow PDA cells to survive and thrive in harsh environments that may lack nutrients and oxygen. Not surprisingly, given its central role in the pathogenesis of this tumor, oncogenic Kras plays a critical role in much of the metabolic reprogramming seen in PDA. In this review, we discuss the metabolic landscape of PDA tumors, including the molecular underpinnings of the key regulatory nodes, and describe how such pathways can be exploited for future diagnostic and therapeutic approaches.
KRAS plays critical roles in regulating a range of normal cellular events as well as pathological processes in many tissues mediated through a variety of signaling pathways, including ERK1/2 and AKT ...signaling, in a cell-, context- and development-dependent manner. The
in vivo
function of KRAS and its downstream targets in gonadal steroidogenic cells for the development and homeostasis of reproductive functions remain to be determined. To understand the functions of KRAS signaling in gonadal theca and interstitial cells, we generated a
Kras
mutant (
tKrasMT
) mouse line that selectively expressed a constitutively active
Kras
G12D
in these cells.
Kras
G12D
expression in ovarian theca cells did not block follicle development to the preovulatory stage. However,
tKrasMT
females failed to ovulate and thus were infertile. The phosphorylated ERK1/2 and forkhead box O1 (FOXO1) and total FOXO1 protein levels were markedly reduced in
tKrasMT
theca cells.
Kras
G12D
expression in theca cells also curtailed the phosphorylation of ERK1/2 and altered the expression of several ovulation-related genes in gonadotropin-primed granulosa cells. To uncover downstream targets of KRAS/FOXO1 signaling in theca cells, we found that the expression of bone morphogenic protein 7 (
Bmp7
), a theca-specific factor involved in ovulation, was significantly elevated in
tKrasMT
theca cells. Chromosome immunoprecipitation assays demonstrated that FOXO1 interacted with the
Bmp7
promoter containing forkhead response elements and that the binding activity was attenuated in
tKrasMT
theca cells. Moreover,
Foxo1
knockdown caused an elevation, whereas
Foxo1
overexpression resulted in an inhibition of
Bmp7
expression, suggesting that KRAS signaling regulates FOXO1 protein levels to control
Bmp7
expression in theca cells. Thus, the anovulation phenotype observed in
tKrasMT
mice may be attributed to aberrant KRAS/FOXO1/BMP7 signaling in theca cells. Our work provides the first
in vivo
evidence that maintaining normal KRAS activity in ovarian theca cells is crucial for ovulation and female fertility.
Background
Cell-free DNA (cfDNA) has arisen as an alternative target for evaluating somatic mutations in cancer. KRAS mutation status is critical for targeted therapy in colorectal adenocarcinoma ...(CRAC). We evaluated KRAS
G12/G13
mutations in cfDNA extracted from serum and compared the results with KRAS
G12/G13
mutations detected in tissue samples. We assessed the clinical significance of KRAS
G12/G13
mutation in serum in regard to recurrence and metastasis of CRAC.
Methods
A total of 146 CRAC patients were enrolled, and KRAS
G12/G13
mutations were evaluated in 146 pairs of serum and tissue samples. In addition, 35 pairs of primary and metastatic CRAC tissue samples were evaluated for KRAS
G12/G13
mutational status.
Results
Detection of KRAS
G12/13
mutation from serum and tissue had a 55% concordance rate, and serum detection had a sensitivity of 39.8%. Detection of the KRAS
G12/13
mutation yielded a 14% discordance rate between primary and metastatic tissue. CRAC patients with mutant KRAS
G12/13
mutation in serum but wild-type KRAS
G12/13
in tissue had concurrent KRAS
G12/13
-mutant metastatic tumors, indicating spatial genetic heterogeneity. Changes in serum KRAS
G12/G13
mutation status during postoperative follow-up were associated with recurrence. Conclusion: Although serum detection of the KRAS
G12/13
mutation cannot substitute for detection in tissue, serum testing can support the interpretation of a CRAC patient’s status in regard to concurrent metastasis. Dynamic changes in serum KRAS
G12/13
mutation status during follow-up indicated that cfDNA from serum represents a potential source for monitoring recurrence in CRAC patients.
Mitochondria undergo fission and fusion to maintain homeostasis, and tumors exhibit the dysregulation of mitochondrial dynamics. We recently demonstrated that ectopic HRasG12V promotes mitochondrial ...fragmentation and tumor growth through Erk phosphorylation of the mitochondrial fission GTPase Dynamin-related protein 1 (Drp1). However, the role of Drp1 in the setting of endogenous oncogenic KRas remains unknown. Here, we show that Drp1 is required for KRas-driven anchorage-independent growth in fibroblasts and patient-derived pancreatic cancer cell lines, and it promotes glycolytic flux, in part through the regulation of hexokinase 2 (HK2). Furthermore, Drp1 deletion imparts a significant survival advantage in a model of KRas-driven pancreatic cancer, and tumors exhibit a strong selective pressure against complete Drp1 deletion. Rare tumors that arise in the absence of Drp1 have restored glycolysis but exhibit defective mitochondrial metabolism. This work demonstrates that Drp1 plays dual roles in KRas-driven tumor growth: supporting both glycolysis and mitochondrial function through independent mechanisms.
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•Drp1 is required for oncogenic KRas-driven transformation•Drp1 promotes KRas-driven glycolysis•Loss of Drp1 inhibits pancreatic tumorigenesis•Loss of Drp1 impairs mitochondrial metabolism in tumor cells
Nagdas et al. find that the mitochondrial fission GTPase Drp1 is required for KRas-driven transformation and pancreatic tumor growth. The inhibition of Drp1 in cells expressing oncogenic KRas leads to impaired glycolytic flux and the eventual loss of mitochondrial metabolic function.
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