Antiplatelet drugs may increase the risk for checkpoint inhibitor-related pneumonitis in advanced cancer patients

BACKGROUND

Immune checkpoint inhibitors (ICIs) are indicated for various cancers and are the mainstay of cancer immunotherapy. They are often associated with ICI-related pneumonitis (CIP), however, hindering a favorable clinical course. Recently, non-oncology concomitant drugs have been reported to affect the efficacy and toxicity of ICIs; however, the association between these drugs and the risk for CIP is uncertain. The aim of this study was to assess the impact of baseline concomitant drugs on CIP incidence in ICI-treated advanced cancer patients.

PATIENTS AND METHODS

This was a single-center retrospective study that included a cohort of 511 patients with advanced cancer (melanoma and non-small-cell lung, head and neck, genitourinary, and other types of cancer) treated with ICIs. Univariable analysis was conducted to identify baseline co-medications associated with CIP incidence. A propensity score matching analysis was used to adjust for potential CIP risk factors, and multivariable analysis was carried out to assess the impact of the identified co-medications on CIP risk.

RESULTS

Forty-seven (9.2%) patients developed CIP. In these patients, the organizing pneumonia pattern was the dominant radiological phenotype, and 42.6% had grade ≥3 CIP, including one patient with grade 5. Of the investigated baseline co-medications, the proportion of antiplatelet drugs (n = 50, 9.8%) was higher in patients with CIP (23.4% versus 8.4%). After propensity score matching, the CIP incidence was higher in patients with baseline antiplatelet drugs (22% versus 6%). Finally, baseline antiplatelet drug use was demonstrated to increase the risk for CIP incidence regardless of cancer type (hazard ratio, 3.46; 95% confidence interval 1.21-9.86).

CONCLUSIONS

An association between concomitant antiplatelet drug use at baseline and an increased risk for CIP was seen in our database. This implies the importance of assessing concomitant medications for CIP risk management.

Type 1 interferon signature and cytotoxic T lymphocyte activation targeted against sweat ducts in inflammatory acquired idiopathic generalized anhidrosis

BACKGROUND

Acquired idiopathic generalized anhidrosis (AIGA) leads to heat intolerance due to the loss or reduction in thermoregulatory sweating over an extensive area of the body. The pathomechanism of AIGA is still unclear but is believed to be autoimmune.

OBJECTIVES

We investigated the clinical and pathological features of inflammatory AIGA (InfAIGA) and noninflammatory AIGA (non-InfAIGA) within the skin.

METHODS

We compared anhidrotic and normohidrotic skin samples from 30 patients with InfAIGA and non-InfAIGA, as well as skin samples of melanocytic nevus as a negative control. We conducted morphometric analysis and immunohistochemical analysis of cell types and expression of inflammatory molecules (TIA1, CXCR3 and MxA). MxA expression was used as a proxy for type 1 interferon activity.

RESULTS

We found that tissue samples from patients with InfAIGA exhibited inflammation within the sweat duct and atrophy of the sweat coil, whereas patients with non-InfAIGA exhibited only atrophy of the sweat coil. Cytotoxic T lymphocyte infiltration and MxA expression were only observed in the sweat ducts of patients with InfAIGA.

CONCLUSIONS

InfAIGA is associated with increased sweat duct inflammation and sweat coil atrophy, whereas non-InfAIGA is only associated with sweat coil atrophy. These data suggest that inflammation leads to epithelial destruction of sweat ducts associated with the sweat coil atrophy and subsequent loss of function. Non-InfAIGA may be regarded as a postinflammatory state of InfAIGA. These observations indicate the contribution of both type 1 and type 2 interferons to sweat gland injury. The mechanism involved is similar to the pathomechanism of alopecia areata (AA).

Einstein-de Haas Nanorotor

We propose a nanoscale rotor embedded between two ferromagnetic electrodes that is driven by spin injection. The spin-rotation coupling allows this nanorotor to continuously receive angular momentum from an injected spin under steady current flow between ferromagnetic electrodes in an antiparallel magnetization configuration. We develop a quantum theory of this angular-momentum transfer and show that a relaxation process from a precession state into a sleeping top state is crucial for the efficient driving of the nanorotor by solving the master equation. Our work clarifies a general strategy for efficient driving of a nanorotor.

Influence of loading rate and limb position on patellar tendon mechanical properties in vivo

BACKGROUND

The aims of this study were to clarify the changes of patellar tendon length during isometric knee joint extension and the double leg squat position using ultrasonography.

METHODS

The left legs of 17 healthy adults were investigated. Isometric knee extension motion was performed at three positions of knee flexion 30° (knee 30°), knee flexion 60° (knee 60°), knee flexion 90° (knee 90°), and at each limb position, 0% (0% peak torque (PT)), 40% (40% PT), 50% (50% PT), and 60% (60% PT) of the maximum knee joint extension torque were executed at random. Both double leg squat motions were randomly performed in three positions: hip flexion 30°, knee flexion 30°, ankle dorsiflexion 10° (squat 30°); hip joint flexion 60°, knee joint flexion 60°, ankle dorsiflexion 20° (squat 60°); and hip joint flexion 90°, knee joint flexion 90°, ankle dorsiflexion 30° (squat 90°). Ultrasonography was used to measure patellar tendon length.

FINDINGS

There were no significant changes in patellar tendon length and strain between knee flexion angles of 30°, 60°, and 90° in isometric knee joint extension and the double leg squat limb position.

INTERPRETATION

The loading rate and limb position do not appear to affect the length and strain of the patellar tendon.

Degranulation and shrinkage of dark cells in eccrine glands and elevated serum carcinoembryonic antigen in patients with acquired idiopathic generalized anhidrosis

BACKGROUND

Acquired idiopathic generalized anhidrosis (AIGA) is characterized by anhidrosis/hypohidrosis without other autonomic and neurological dysfunctions. Pathologically, AIGA is considered to usually present no significant morphological alterations in eccrine glands, the secretory portion which consists of clear cells, dark cells, and myoepithelial cells. AIGA patients recently have been reported to show high serum concentrations of carcinoembryonic antigen (CEA).

OBJECTIVE

Our aim is to reveal morphological abnormalities of dark cells and investigate their relationship with serum CEA.

METHODS

We performed comparative analysis of eccrine glands between sweat-preserved and non-sweating skin in four AIGA patients. Serum CEA concentrations in 22 cases with AIGA were measured with healthy volunteers. Furthermore, we semiquantitatively investigated dermcidin, FoxA1 and CEA expression in eccrine glands of 12 cases with AIGA and 5 cases with non-AIGA.

RESULTS

Marked degranulation and shrinkage of dark cells consistently occurred in AIGA. Furthermore, high serum CEA concentrations were found in 14 of 22 AIGA patients (over 60%), but serum CEA levels were not correlated with CEA expression in eccrine glands. Dermcidin expression in dark cells apparently decreased in AIGA patients, severely in those with high serum CEA and moderately in those with low serum CEA, while well-preserved expression was found in non-AIGA subjects.

CONCLUSION

Our study suggests morphological damage and molecular dysregulation of dark cells, leading to impairment of their functions in AIGA patients. Severely damaged dark cells correspond to high serum CEA. Accordingly, these pathological changes in eccrine dark cells may be involved in anhidrosis/hypohidrosis of AIGA.

Squamous cell carcinoma arising from lupus vulgaris with a >60-year history

We report the case of a 71-year-old Japanese man with squamous cell carcinoma arising from lupus vulgaris on the face, >60 years after the appearance of the lupus vulgaris. The red plaque on the patient's face had been diagnosed as a hemangioma or rosacea at several hospitals, although he had had lung tuberculosis at the age of 4 and his father died from lung tuberculosis at 38 years of age. Although lupus vulgaris was the most frequent clinical form of true skin tuberculosis until the 1960s, it has become rare since then. Malignant tumors are known to occur in individuals with lupus vulgaris, with a reported rate of 0.5-10.5%. In light of Japan's "graying society," tuberculosis is still an important disorder, and clinicians must remain aware of cutaneous tuberculosis.

Fish collagen is an important panallergen in the Japanese population

Collagen was identified as a fish allergen in early 2000s. Although its allergenic potential has been suggested to be low, risks associated with collagen as a fish allergen have not been evaluated to a greater extent. In this study, we aimed to clarify the importance of collagen as a fish allergen. Our results showed that 50% of Japanese patients with fish allergy had immunoglobulin E (IgE) against mackerel collagen, whereas 44% had IgE against mackerel parvalbumin. IgE inhibition assay revealed high cross-reactivity of mackerel collagen to 22 fish species (inhibition rates: 87-98%). Furthermore, a recently developed allergy test demonstrated that collagen triggered IgE cross-linking on mast cells. These data indicate that fish collagen is an important and very common panallergen in fish consumed in Japan. The high rate of individuals' collagen allergy may be attributable to the traditional Japanese custom of raw fish consumption.

Phase II study of the immune-checkpoint inhibitor ipilimumab plus dacarbazine in Japanese patients with previously untreated, unresectable or metastatic melanoma

PURPOSE

Ipilimumab (IPI), a monoclonal antibody against immune-checkpoint receptor cytotoxic T lymphocyte antigen-4, is designed to enhance antitumor T cell function. IPI 10 mg/kg plus dacarbazine (DTIC) significantly improved overall survival in a phase 3 study involving predominantly Caucasian patients, with an adverse event (AE) profile similar to that of IPI monotherapy. We conducted a single-arm, phase 2 study to evaluate the safety and efficacy of IPI plus DTIC in Japanese patients.

METHODS

Previously untreated patients with unresectable stage III or IV melanoma received IPI 10 mg/kg plus DTIC 850 mg/m(2) every 3 weeks for four doses (q3w × 4), followed by DTIC q3w × 4 and then IPI every 12 weeks until disease progression or intolerable toxicity.

RESULTS

All 15 treated patients reported drug-related AEs, the most common of which were increases in alanine aminotransferase (n = 12, 80 %) and aspartate aminotransferase (n = 11, 73 %). Treatment-related serious AEs were reported in 11 (73 %) patients. Nine patients (60 %) discontinued treatment due to drug-related toxicities. Immune-related AEs (irAEs) were reported in 14 patients (93 %). The most frequent irAEs were liver (n = 12, 80 %) and skin (n = 10, 67 %) toxicities. Five deaths were reported; all were caused by progressive disease. Efficacy evaluation showed one complete response, one partial response and four patients with stable disease. Best overall response rate was 13 % (2/15), and the disease control rate was 40 % (6/15). The study was terminated early due to frequent, high-grade liver toxicities.

CONCLUSIONS

IPI 10 mg/kg plus DTIC 850 mg/m(2) was not considered tolerable in the Japanese patient population. ClinicalTrials.gov identifier: NCT01681212.

Clinical course of drug-induced hypersensitivity syndrome treated without systemic corticosteroids

BACKGROUND/AIM

Drug-induced hypersensitivity syndrome (DIHS) is a severe reaction to drugs which characteristically occurs after a long latency period. In addition, human herpes virus 6 (HHV-6) reactivation is a characteristic finding in DIHS, which has been known to be related to disease severity. Because DIHS has generally been treated by systemic corticosteroids, the natural clinical course is not clear.

METHODS

Data for patients with both DIHS and HHV-6 reactivation were retrospectively collected from four hospitals.

RESULTS

Data were collected on 12 patients ranging in age from 21 to 76 years (median, 65.5). All cases had been suspected of DIHS at their initial visit, and the elevation of serum anti-HHV-6 antibody had been confirmed (4-256 times: median; 32). The culprit drugs were carbamazepine (6), salazosulfapyridine (4), mexiletine (1) and zonisamide (1). The period of latency from the first administration of the drug ranged from 15 to 50 days (median, 30). All patients were treated conservatively for DIHS without systemic corticosteroids. The peaks of the patients' symptoms and laboratory findings were as follows (days from the onset of skin lesions): fever, 4-16 (median, 10.5); liver abnormality, 3-22 (median, 7.5); leukocytosis, 7-20 (median, 9). All patients recovered without pneumonia, myocarditis, nephritis or other systemic disease, from 7 to 37 days (median, 18) after withdrawal of the drug and from 11 to 44 days (median, 21) after the onset of skin lesions.

CONCLUSION

It might be unnecessary to give systemic corticosteroids immediately to all patients suspected of having DIHS.

Mutation analysis of BRAF and KIT in circulating melanoma cells at the single cell level

Background:

The availability of molecular-targeted therapies for the treatment of melanoma has emphasised the need to identify mutations in target genes such as BRAF and KIT. Circulating tumour cells (CTC) are present in the peripheral blood of a significant proportion of cancer patients.

Methods:

High molecular weight melanoma-associated antigen (HMW-MAA) was used to isolate melanoma cells from peripheral blood as it is selectively expressed at high levels on melanomas. The HMW-MAA-positive cells were isolated using immunomagnetic beads. After removing CD45⁺ cells, CTC were identified by staining with MART-1- and gp100-specific antibodies (HMW-MAA⁺, CD45⁻, MART-1/gp100⁺). Single, isolated CTC were then subjected to BRAF and KIT mutational analysis.

Results:

CTC (HMW-MAA⁺, CD45⁻, MART-1/gp100⁺) were isolated from the blood of 11 patients and BRAF and KIT were sequenced in nine and four patients, respectively. The BRAF sequences identified in the CTC were inconsistent with those identified in autologous melanoma tumours in three patients and the KIT sequences were inconsistent in three patients. In addition, polyclonal BRAF mutations were identified in one patient and concomitant mutations in BRAF and KIT were identified in another patient.

Conclusion:

Melanoma cells show clonal heterogeneity. Therefore, CTC genotyping may be crucial for successful molecular-targeted therapy.

The course of pregnancy and childbirth in three mothers with recessive dystrophic epidermolysis bullosa

BACKGROUND

Recessive dystrophic epidermolysis bullosa (RDEB) is an autosomal recessive skin disease caused by mutations in the type VII collagen gene (COL7A1), resulting in detachment of the entire epidermis due to loss or hypoplasticity of the anchoring fibrils that normally secure the basement membrane to the underlying dermis. Trauma-induced blistering is often complicated by chronic erosions and scarring. From that perspective, pregnancy in RDEB might be considered an indication for elective caesarean section in a bid to minimize perineal blistering. To date, only four cases of pregnancy and delivery in patients with RDEB have been reported.

CASES

We report three more women, each with RDEB-generalized other (RDEB-GO), all of whom had successful vaginal deliveries without major cutaneous or mucosal complications. One woman also had a second child, by vaginal delivery, indicating a lack of vaginal stenosis after the first birth.

CONCLUSIONS

These cases show that RDEB-GO is not an absolute primary indication for elective caesarean section and that, perhaps surprisingly, genital/perineal blistering and scarring are not inevitable consequences of childbirth. Moreover, breastfeeding is also feasible in women with RDEB-GO.

Cutaneous accumulation of abnormal polyglutamine proteins of patients with dentatorubral-pallidoluysian atrophy

BACKGROUND AND PURPOSE

Dentatorubral-pallidoluysian atrophy (DRPLA) is a hereditary spinocerebellar degeneration caused by expansion of a trinucleotide CAG repeat encoding a polyglutamine tract in a disease protein atrophin-1. The clinical features include ataxia, choreoathetosis, and dementia, which result from neural degeneration caused by the mutant atrophin-1.

METHODS

We performed skin biopsy in two patients with DRPLA.

RESULTS

We found multiple clear cells in the epidermis, which were positive for proteins containing an expanded polyglutamine stretches. The clear cells were p63 (+), S-100 (-), and cytokeratin 20 (-), showing that they were keratinocytes. Negative or weak signals of pan-cytokeratin were consistent with the finding of decreased tonofilaments at the electron microscopic level.

CONCLUSIONS

The presence of clear keratincoytes showed that the mutant proteins interfered in cellular functions not only in neural cells but also in keratinocytes. The skin is accessible by biopsy, making it important in the diagnosis. Furthermore, the polyglutamine staining in the skin may be useful for evaluation of therapeutic modalities for DRPLA and other polyglutamine diseases.

Profiles of Foxp3+ regulatory T cells in eczematous dermatitis, psoriasis vulgaris and mycosis fungoides

BACKGROUND

It is well known that regulatory T cells (Tregs), identified by their expression of CD4, CD25 and Foxp3, play a crucial role in maintaining peripheral tolerance. Recently, it has been demonstrated that a Treg population resides in normal human skin. However, only a few studies have demonstrated the presence of Foxp3+ Tregs in inflammatory skin disorders.

OBJECTIVES

In this study, we immunohistologically examined the presence of CD4+ CD25+ Foxp3+ Tregs in the lesional skin of psoriasis vulgaris, mycosis fungoides and eczematous dermatitis.

METHODS

We used immunohistochemistry to examine the presence of Foxp3+ Tregs in fixed sections of the lesional skin from 16 patients with psoriasis vulgaris, 17 patients with mycosis fungides and 18 patients with eczematous dermatitis in addition to 10 normal skin samples.

RESULTS

In normal skin, epidermal and dermal Foxp3+ cells were rare. The psoriasis vulgaris, mycosis fungoides and eczematous dermatitis samples contained substantial numbers of epidermal and dermal CD3+, CD4+ and CD25+ Foxp3+ Tregs. The epidermis contained a higher percentage of CD3+, CD4+ and CD25+ Foxp3+ cells than the dermis. The percentage of Foxp3+ cells among CD3+ or CD4+ cells was significantly lower in eczematous dermatitis than in psoriasis vulgaris or mycosis fungoides, and that of dermal Foxp3+ cells was significantly lower in psoriasis vulgaris than in eczematous dermatitis or mycosis fungoides.

CONCLUSIONS

The lower percentage of epidermal or dermal Foxp3+ cells in eczematous dermatitis or psoriasis vulgaris, respectively, might contribute to their pathogenesis.

p51/p63 Inhibits ultraviolet B-induced apoptosis via Akt activation

The epidermis must be protected against excess apoptotic cell death in response to ultraviolet-B (UV-B) irradiation. p53 is known to be critical for this protection. Although the p53 family member DeltaNp51B/DeltaNp63alpha (an N terminal-deleted form of p51/p63) is abundantly expressed in keratinocytes, its contribution to UV-B-dependent apoptosis is largely unknown. We found that, after a transient increase, DeltaNp51B is downregulated in UV-B-irradiated keratinocytes undergoing apoptosis, whereas p53 is upregulated with delayed kinetics. Furthermore, the reduction of DeltaNp51B by small interfering RNAs augmented UV-B-dependent apoptosis in keratinocytes, indicating that DeltaNp51B blocks keratinocyte apoptosis. Although the exogenous expression of DeltaNp51B in keratinocytes did not further block the UV-B-dependent apoptosis, to our surprise the expression of TAp51B (an isoform with a full NH(2)-terminal transactivation domain that is structurally and functionally similar to p53) decreased apoptosis significantly. The blockade of keratinocyte apoptosis by the p51 was dependent on the phosphorylation of Akt, resulting in the activation of a survival pathway. Thus, in addition to its indispensable roles in epithelial development, p51 acts in adult cells to protect the epidermis against UV-B irradiation by preventing excess depletion of keratinocytes.

p53 homologue, p51/p63, maintains the immaturity of keratinocyte stem cells by inhibiting Notch1 activity

p53 homologue, p51/p63, predominantly expressed in keratinocyte stem cells, is indispensable for the formation of epidermis. Notch1, another such gene indispensable for the process, induces growth arrest and differentiation in keratinocytes. We found that exogenous expression of DeltaNp51B (DeltaNp63alpha), one of the isoforms of p51 specifically expressed in basal keratinocytes, blocked Notch 1-dependent growth arrest and differentiation in mouse keratinocytes by inhibiting p21 expression and maintaining integrins expression. Furthermore, DeltaNp51B by itself was found to have ability to induce expression of integrin alpha6beta4, which promotes attachment of basal cells to basal membrane thereby keeping the cells in immature state. Therefore, we conclude that DeltaNp51B expression warrants integrin expression even under the influence of Notch1 and that DeltaNp51B is a long-sought factor required to maintain basal cell keratinocytes immaturity by inhibiting Notch1 activity. We will postulate a plausible model explaining the maintenance of the squamous epithelium architectures as well as offering mechanistic explanations for pathological features of skin diseases, including cancers, psoriasis along with physiological wound healings.

Effects of heat stress and mechanical stretch on protein expression in cultured skeletal muscle cells

Effects of heat stress, mechanical stretching or a combination of both on the expression of heat shock proteins (HSPs) and total protein level were studied in a culture system. Rat skeletal muscle cells (L6) were cultured on flexible-bottomed culture plates. They were subjected to one of the four following conditions: (1) 97 h incubation at 37 degrees C, (2) 1 h incubation at 41 degrees C followed by 96 h incubation at 37 degrees C, (3) 1 h incubation at 37 degrees C followed by 96 h cyclic stretching (18% of initial length, 2-s stretch and 4-s release) at 37 degrees C or (4) 1 h incubation at 41 degrees C followed by 96 h cyclic stretching at 37 degrees C. The expression of HSP72 and HSP90 and total protein was determined in the crude homogenates, supernatant and pellets. Cellular protein concentrations in the homogenates and pellets were increased by heat stress and/or mechanical stress (stretch). A cumulative effect of the combination of heating and stretch on the protein concentration in the homogenates and in the pellets was noted. The expressions of HSP72 and HSP90 in the pellets were also increased by heat stress and/or stretch. However, HSP90 in the supernatant did not change following heat stress and/or stretch. The regulation of HSP72 and HSP90 expression in skeletal muscle cells may be closely related to total protein, the abundance of which is also stimulated by mechanical and heat stresses. These observations suggest strongly that heating and passive stretch of muscle may be useful as a means of increasing muscle mass, not only in athletes but also in patients during rehabilitation.

Molecular events occurring behind ultraviolet-induced skin inflammation

We reviewed a recent advance in the studies of the molecular mechanisms for 'ultraviolet responses', paying special attention to two transcription factors, nuclear factor kappa B and p53, and to a balance noted between an anti-apoptotic phosphatidylinositol 3-kinase-Akt pathway and its inhibitory ceramide-caveolin-1 pathway. These studies were mostly carried out using in vitro or animal models. On the basis of these results, we determined that phase by phase molecular events clarified in these studies correspond well with the three phases of ultraviolet-induced inflammation observed, i.e. the early vasodilatory phase, the second inflammatory phase in which many inflammatory cells such as neutrophils and T cells accumulate in the skin, and the last regressive phase based on several anti-inflammatory events.

Cytosolic O-GlcNAc accumulation is not involved in beta-cell death in HIT-T15 or Min6

O-linked N-acetylglucosamine (O-GlcNAc) is attached to and detached from proteins by O-GlcNAc transferase (OGT) and O-GlcNAcase, respectively. It has been proposed that streptozotocin induces pancreatic beta-cell death by blocking O-GlcNAcase and increasing O-GlcNAc. To elucidate the relationship between cytosolic O-GlcNAc accumulation and beta-cell death, we treated beta-cell lines HIT-T15 and Min6 with glucosamine. Glucosamine markedly reduced cell viability in both cell lines only at 10 mM. The measurement of cytosolic O-GlcNAc under glucosamine treatment revealed that O-GlcNAc accumulation was observed even at 2 mM glucosamine and maximized at 5 mM, but did not occur very well at 10 mM. Furthermore, 100 microM PUGNAc, an inhibitor of O-GlcNAcase, increased cytosolic O-GlcNAc but did not induce cell death in these cells. Therefore, no correlation between accumulation of cytosolic O-GlcNAc and beta-cell death was suggested. Alternatively, inosine partially rescued cell death induced by glucosamine in Min6 cells, suggesting that energy depletion partly contributes to beta-cell death by glucosamine.

Maximal and submaximal forces of slow fibers in human soleus after bed rest

The effects of 2 and 4 mo of bed rest, with or without exercise countermeasures, on the contractile properties of slow fibers in the human soleus muscle were examined. Mean fiber diameters were 8 and 36% smaller after 2 and 4 mo of bed rest, respectively, than the pre-bed rest level. Maximum tetanic force (P(o)), maximum activated force (F(max)) per cross-sectional area (CSA), and the common-logarithm value of free Ca(2+) concentration required for half-maximal activation (pCa(50)) also decreased after 2 and 4 mo of bed rest. In contrast, maximum unloaded shortening velocity (V(o)) was increased after 2 and 4 mo of bed rest. After 1 mo of recovery, fiber diameters, P(o), F(max) per CSA (P > 0.05), and pCa(50) were increased and V(o) decreased toward pre-bed rest levels. Effects of knee extension/flexion exercise by wearing an anti-G Penguin suit for 10 h daily, and the effects of loading or unloading of the plantar flexors with (Penguin-1) or without (Penguin-2) placing the elastic loading elements of the suit, respectively, were investigated during ~2 mo of bed rest. In the Penguin-1 group, mean fiber diameter, P(o), F(max) per CSA, V(o), and pCa(50) were similar before and after bed rest. However, the responses of fiber size and contractile properties to bed rest were not prevented in the Penguin-2 group, although the degree of the changes was less than those induced by bed rest without any countermeasure. These results indicate that long-term bed rest results in reductions of fiber size, force-generation capacity, and Ca(2+) sensitivity, and enhancement of shortening velocity in slow fibers of the soleus. The data indicate that continuous mechanical loading on muscle, such as stretching of muscle, is an effective countermeasure for the prevention of muscular adaptations to gravitational unloading.

p21(WAF1/Cip1) functions as a suppressor of malignant skin tumor formation and a determinant of keratinocyte stem-cell potential

p21(WAF1/Cip1) is one of the best characterized downstream targets of p53, and the growth suppressing function of this cyclin-dependent kinase inhibitor is well established. However, whether p21 exerts a tumor-suppressing function of its own remains to be established. We report here that, similarly to loss of p53, disruption of the p21(WAF1/Cip1) gene results in a markedly increased susceptibility to chemically induced skin carcinoma formation, whereas the number of papillomas is reduced. Previous evidence indicates that malignant versus benign keratinocyte tumor formation is likely to involve distinct target-cell populations with a different commitment to differentiation. In parallel with the increased susceptibility to carcinoma formation, loss of p21(WAF1/Cip1) was found to promote keratinocyte subpopulations with increased growth/differentiation potential, including clonal growth capability, reversible commitment to differentiation, and capability to generate all types of terminally differentiated keratinocytes present in vivo, not only in the interfollicular epidermis but also in hair follicles. Thus, these findings have revealed a function of p21 as a suppressor of malignant but not benign skin-tumor formation and a determinant of the growth/differentiation potential of keratinocyte subpopulations.